| By Author | [ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z | Other Symbols ] |
| By Title | [ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z | Other Symbols ] |
| By Language |
|
Download this book: [ ASCII | HTML | PDF ] Look for this book on Amazon Tweet |
Title: Human Foods and Their Nutritive Value
Author: Snyder, Harry
Language: English
As this book started as an ASCII text book there are no pictures available.
*** Start of this LibraryBlog Digital Book "Human Foods and Their Nutritive Value" ***
This book is indexed by ISYS Web Indexing system to allow the reader find any word or number within the document.
VALUE***
Transcribers note:
In this text, subscripted numbers are represented thus: _{12}
HUMAN FOODS AND THEIR NUTRITIVE VALUE
by
HARRY SNYDER, B.S.
New York
The MacMillan Company
1914
All rights reserved
Copyright, 1908,
by the MacMillan Company.
Set up and electrotyped. Published November, 1908. Reprinted
October, 1909; September, 1910; February, 1911; September, 1912;
May, December, 1913; June, 1914.
Norwood Press
J. S. Cushing Co.--Berwick & Smith Co.
Norwood, Mass., U.S.A.
PREFACE
Since 1897 instruction has been given at the University of Minnesota,
College of Agriculture, on human foods and their nutritive value. With
the development of the work, need has been felt for a text-book
presenting in concise form the composition and physical properties of
foods, and discussing some of the main factors which affect their
nutritive value. To meet the need, this book has been prepared,
primarily for the author's classroom. It aims to present some of the
principles of human nutrition along with a study of the more common
articles of food. It is believed that a better understanding of the
subject of nutrition will suggest ways in which foods may be selected
and utilized more intelligently, resulting not only in pecuniary saving,
but also in greater efficiency of physical and mental effort.
Prominence is given in this work to those foods, as flour, bread,
cereals, vegetables, meats, milk, dairy products, and fruits, that are
most extensively used in the dietary, and to some of the physical,
chemical, and bacteriological changes affecting digestibility and
nutritive value which take place during their preparation for the table.
Dietary studies, comparative cost and value of foods, rational feeding
of men, and experiments and laboratory practice form features of the
work. Some closely related topics, largely of a sanitary nature, as the
effect upon food of household sanitation and storage, are also briefly
discussed. References are given in case more extended information is
desired on some of the subjects treated. While this book was prepared
mainly for students who have taken a course in general chemistry, it has
been the intention to present the topics in such a way as to be
understood by the layman also.
This work completes a series of text-books undertaken by the author
over ten years ago, dealing with agricultural and industrial subjects:
"Chemistry of Plant and Animal Life," "Dairy Chemistry," "Soils and
Fertilizers," and "Human Foods and their Nutritive Value." It has been
the aim in preparing these books to avoid as far as possible repetition,
but at the same time to make each work sufficiently complete to permit
its use as a text independent of the series.
One of the greatest uses that science can serve is in its application to
the household and the everyday affairs of life. Too little attention is
generally bestowed upon the study of foods in schools and colleges, and
the author sincerely hopes the time will soon come when more prominence
will be given to this subject, which is the oldest, most important, most
neglected, and least understood of any that have a direct bearing upon
the welfare of man.
HARRY SNYDER.
CONTENTS
CHAPTER I
PAGE
GENERAL COMPOSITION OF FOODS 1
Water; Dry Matter; Variations in Weight of Foods;
Ash; Function of Ash in Plant Life; Organic Matter;
Products of Combustion of Organic Matter; Classification
of Organic Compounds; Non-nitrogenous Compounds;
Carbohydrates; Cellulose; Amount of Cellulose in Foods;
Crude Fiber; Starch; Microscopic Structure of Starch;
Dextrin; Food Value of Starch; Sugar; Pectose Substances;
Nitrogen-free-extract; Fats; Fuel Value of Fats;
Iodine Number of Fats; Glycerol Content of Fats; Ether
Extract and Crude Fat; Organic Acids; Dietetic Value
of Organic Acids; Essential Oils; Mixed Compounds;
Nutritive Value of Non-nitrogenous Compounds; Nitrogenous
Compounds; General Composition; Protein; Sub-divisions
of Proteins; Crude Protein; Food Value of
Protein; Albuminoids; Amids and Amines; Alkaloids;
General Relationship of the Nitrogenous Compounds.
CHAPTER II
CHANGES IN COMPOSITION OF FOODS DURING COOKING AND
PREPARATION 27
Raw and Cooked Foods compared as to Composition;
Chemical Changes during Cooking; General Changes
affecting Cellulose, Starch, Sugar, Pectin Bodies, Fats,
Proteids; Effect of Chemical Changes on Digestibility;
Physical Changes during Cooking; Action of Heat on
Animal and Plant Tissues; Amount of Heat required for
Cooking; Bacteriological Changes; Insoluble Ferments;
Soluble Ferments; Bacterial Action Necessary in Preparation
of Some Foods; Injurious Bacterial Action; General
Relationship of Chemical, Physical, and Bacteriological
Changes; Esthetic Value of Foods; Color of Foods;
Natural and Artificial Colors; Conditions under which
Use of Chemicals in Preparation of Foods is Justifiable.
CHAPTER III
VEGETABLE FOODS 37
General Composition; Potatoes; Chemical and Mechanical
Composition; Uses of Potatoes in Dietary; Sweet
Potatoes; Carrots; Parsnips; Cabbage; Cauliflower;
Beets; Cucumbers; Lettuce; Onions; Spinach; Asparagus;
Melons; Tomatoes; Sweet Corn; Eggplant;
Squash; Celery; Dietetic Value of Vegetables; Nutrient
Content of Vegetables; Sanitary Condition of Vegetables;
Miscellaneous Compounds in Vegetables; Canned Vegetables;
Edible Portion and Refuse of Vegetables.
CHAPTER IV
FRUITS, FLAVORS AND EXTRACTS 48
General Composition; Food Value; Apples; Oranges;
Lemons; Grape Fruit; Strawberries; Grapes; Peaches;
Plums; Olives; Figs; Dried Fruits; Uses of Fruit in
the Dietary; Canning and Preservation of Fruits; Adulterated
Canned Fruits; Fruit Flavors and Extracts; Synthetic
Preparation of Flavors.
CHAPTER V
SUGARS, MOLASSES, SYRUP, HONEY, AND CONFECTIONS 58
Composition of Sugars; Beet Sugar; Cane Sugar;
Manufacture of Sugar; Sulphur Dioxid and Indigo, Uses
of, in Sugar Manufacture; Commercial Grades of Sugar;
Sugar in the Dietary; Maple Sugar; Adulteration of
Sugar; Dextrose Sugars; Inversion of Sugars; Molasses;
Syrups; Adulteration of Molasses; Sorghum Syrup;
Maple Syrup; Analysis of Sugar; Adulteration of Syrups;
Honey; Confections; Coloring Matter in Candies; Coal
Tar Dyes; Saccharine.
CHAPTER VI
LEGUMES AND NUTS 71
General Composition of Legumes; Beans; Digestibility
of Beans; Use of Beans in the Dietary; String
Beans; Peas; Canned Peas; Peanuts; General Composition
of Nuts; Chestnuts; The Hickory Nut; Almonds;
Pistachio; Cocoanuts; Uses of Nuts in the Dietary.
CHAPTER VII
MILK AND DAIRY PRODUCTS 80
Importance in the Dietary; General Composition; Digestibility;
Sanitary Condition of Milk; Certified Milk;
Pasteurized Milk; Tyrotoxicon; Color of Milk; Souring
of Milk; Use of Preservatives in Milk; Condensed Milk;
Skim Milk; Cream; Buttermilk; Goat's Milk; Koumiss;
Prepared Milks; Human Milk; Adulteration of Milk;
Composition of Butter; Digestibility of Butter; Adulteration
of Butter; General Composition of Cheese;
Digestibility; Use in the Dietary; Cottage Cheese; Different
Kinds of Cheese; Adulteration of Cheese; Dairy
Products in the Dietary.
CHAPTER VIII
MEATS AND ANIMAL FOOD PRODUCTS 98
General Composition; Mineral Matter; Fat; Protein;
Non-nitrogenous Compounds; Why Meats vary in Composition;
Amides; Albuminoids; Taste and Flavor of
Meats; Alkaloidal Bodies in Meats; Ripening of Meats
in Cold Storage; Beef; Veal; Mutton; Pork; Lard;
Texture and Toughness of Meat; Influence of Cooking
upon the Composition of Meats; Beef Extracts; Miscellaneous
Meat Products; Pickled Meats; Saltpeter in
Meats; Smoked Meats; Poultry; Fish; Oysters, Fattening
of; Shell Fish; Eggs, General Composition; Digestibility
of Eggs; Use of Eggs in the Dietary; Canned
Meats, General Composition.
CHAPTER IX
CEREALS 121
Preparation and Cost of Cereals; Various Grains used
in making Cereal Products; Cleanliness of; Corn Preparations;
Corn Flour; Use of Corn in Dietary; Corn Bread;
Oat Preparations; Cooking of Oatmeal; Wheat Preparations;
Flour Middlings; Breakfast Foods; Digestibility
of Wheat Preparations; Barley Preparations; Rice Preparations;
Predigested Foods; The Value of Cereals in the
Dietary; Phosphate Content of Cereals; Phosphorus Requirements
of a Ration; Mechanical Action of Cereals
upon Digestion; Cost and Nutritive Value of Cereals.
CHAPTER X
WHEAT FLOUR 133
Use for Bread Making; Winter and Spring Wheat
Flours; Composition of Wheat and Flour; Roller Process
of Flour Milling; Grades of Flour; Types of Flour; Composition
of Flour; Graham and Entire Wheat Flours;
Composition of Wheat Offals; Aging and Curing of Flour;
Macaroni Flour; Color; Granulation; Capacity of Flour
to absorb Water; Physical Properties of Gluten; Gluten
as a Factor in Bread Making; Unsoundness; Comparative
Baking Tests; Bleaching; Adulteration of Flour; Nutritive
Value of Flour.
CHAPTER XI
BREAD AND BREAD MAKING 158
Leavened and Unleavened Bread; Changes during
Bread Making; Loss of Dry Matter during Bread Making;
Action of Yeast; Compressed Yeast; Dry Yeast; Production
of Carbon Dioxid Gas and Alcohol; Production
of Soluble Carbohydrates; Production of Acids in Bread
Making; Volatile Compounds produced during Bread
Making; Behavior of Wheat Proteids in Bread Making;
Production of Volatile Nitrogenous Compounds; Oxidation
of Fat; Influence of the Addition of Wheat Starch
and Gluten to Flour; Composition of Bread; Use of
Skim Milk and Lard in Bread Making; Influence of
Warm and Cold Flours in Bread Making; Variations in
the Process of Bread Making; Digestibility of Bread;
Use of Graham and Entire Wheat in the Dietary; Mineral
Content of White Bread; Comparative Digestibility
of New and Old Bread; Different Kinds of Bread; Toast.
CHAPTER XII
BAKING POWDERS 186
General Composition; Cream of Tartar Powders; Residue
from Cream of Tartar Baking Powders; Tartaric
Acid Powders; Phosphate Baking Powders; Mineral and
Organic Phosphates; Phosphate Residue; Alum Baking
Powders; Residue from Alum Baking Powders; Objections
urged against Alum Powders; Action of Baking
Powders and Yeast Compared; Keeping Qualities of
Baking Powders; Inspection of Baking Powders; Fillers;
Home-made Baking Powders.
CHAPTER XIII
VINEGAR, SPICES, AND CONDIMENTS 193
Vinegar; Chemical Changes during Manufacture of
Vinegar; Ferment Action; Materials used in Preparation
of Vinegars; Characteristics of a Good Vinegar; Vinegar
Solids; Acidity of Vinegar; Different Kinds of Vinegars;
Standards of Purity; Adulteration of Vinegar; Characteristics
of Spices; Pepper; Cayenne; Mustard; Ginger;
Cinnamon and Cassia; Cloves; Allspice; Nutmeg; Adulteration
of Spices and Condiments; Essential Oils of;
Uses of Condiments in Preparation of Foods; Action of
Condiments upon Digestion; Condiments and Natural
Flavors.
CHAPTER XIV
TEA, COFFEE, CHOCOLATE, AND COCOA 203
Tea; Sources of Tea Supply; Composition of Tea;
Black Tea and Green Tea; Judging Teas; Adulteration
of Tea; Food Value and Physiological Properties of Tea;
Composition of Coffee; Adulteration of Coffee; Chicory
in Coffee; Glazing of Coffee; Cereal Coffee Substitutes;
Cocoa and Chocolate Preparations; Composition of Cocoa;
Chocolate; Cocoa Nibs; Plain Chocolate; Sweet Chocolate;
Cocoa Butter; Nutritive Value of Cocoa; Adulteration
of Chocolate and Cocoa; Comparative Composition
of Beverages.
CHAPTER XV
THE DIGESTIBILITY OF FOOD 214
Digestibility, how Determined; Completeness and Ease
of Digestion Process; Example of Digestion Experiment;
Available Nutrients; Available Energy; Caloric Value of
Foods; Normal Digestion and Health; Digestibility of
Animal Foods; Digestibility of Vegetable Foods; Factors
influencing Digestion; Combination of Foods; Amount
of Food; Method of Preparation of Food; Mechanical
Condition of Foods; Mastication; Palatability of Foods;
Physiological Properties of Foods; Individuality; Psychological
Factors.
CHAPTER XVI
COMPARATIVE COST AND VALUE OF FOODS 231
Cost and Nutrient Content of Foods; How to compare
Two Foods as to Nutritive Value; Cheap Foods; Expensive
Foods; Nutrients Procurable for a Given Sum; Examples;
Comparing Nutritive Value of Common Foods
at Different Prices; Cost and Value of Nutrients.
CHAPTER XVII
DIETARY STUDIES 244
Object of Dietary Studies; Wide and Narrow Rations;
Dietary Standards; Number of Meals per Day; Mixed
Dietary Desirable; Animal and Vegetable Foods;
Economy of Production; Food Habits; Underfed Families;
Cheap and Expensive Foods; Food Notions;
Dietary of Two Families Compared; Food in its Relation
to Mental and Physical Vigor; Dietary Studies in Public
Institutions.
CHAPTER XVIII
RATIONAL FEELING OF MAN 261
Object; Human and Animal Feeding Compared; Standard
Rations; Why Tentative Dietary Standards; Amounts
of Food Consumed; Average Composition of Foods;
Variations in Composition of Foods; Example of a Ration;
Calculations of Balanced Rations; Requisites of a
Balanced Ration; Examples; Calculations of Rations for
Men at Different Kinds of Labor.
CHAPTER XIX
WATER 268
Importance; Impurities in Water; Mineral Impurities;
Organic Impurities; Interpretation of a Water Analysis;
Natural Purification of Water; Water in Relation to
Health; Improvement of Waters; Boiling of Water; Filtration;
Purification of Water by Addition of Chemicals;
Ice; Rain Waters; Waters of High and Low Purity;
Chemical Changes which Organic Matter of Water Undergoes;
Bacterial Content of Water; Mineral Waters;
Materials for Softening Water; Uses of; Economic Value
of a Pure Water Supply.
CHAPTER XX
FOOD AS AFFECTED BY HOUSEHOLD SANITATION AND
STORAGE 284
Injurious Compounds in Foods; Nutrient Content and
Sanitary Condition of Food; Sources of Contamination
of Food; Unclean Ways of Handling Food; Sanitary Inspection
of Food; Infection from Impure Air; Storage
of Food in Cellars; Respiration of Vegetable Cells; Sunlight,
Pure Water, and Pure Air as Disinfectants; Foods
contaminated from Leaky Plumbing; Utensils for Storage
of Food; Contamination from Unclean Dishcloths; Refrigeration;
Chemical Changes that take Place in the
Refrigerator; Soil; Disposal of Kitchen Refuse; Germ
Diseases spread by Unsanitary Conditions around Dwellings
due to Contamination of Food; General Considerations;
Relation of Food to Health.
CHAPTER XXI
LABORATORY PRACTICE 299
Object of Laboratory Practice; Laboratory Note-book
and Suggestions for Laboratory Practice; List of Apparatus
Used; Photograph of Apparatus Used; Directions
for Weighing; Directions for Measuring; Use of Microscope;
Water in Flour; Water in Butter; Ash in Flour;
Nitric Acid Test for Nitrogenous Organic Matter; Acidity
of Lemons; Influence of Heat on Potato Starch Grains;
Influence of Yeast on Starch Grains; Mechanical Composition
of Potatoes; Pectose from Apples; Lemon Extract;
Vanilla Extract; Testing Olive Oil for Cotton Seed Oil;
Testing for Coal Tar Dyes; Determining the Per Cent of
Skin in Beans; Extraction of Fat from Peanuts; Microscopic
Examination of Milk; Formaldehyde in Cream or
Milk; Gelatine in Cream or Milk; Testing for Oleomargarine;
Testing for Watering or Skimming of Milk; Boric
Acid in Meat; Microscopic Examination of Cereal Starch
Grains; Identification of Commercial Cereals; Granulation
and Color of Flour; Capacity of Flour to absorb
Water; Acidity of Flour; Moist and Dry Gluten; Gliadin
from Flour; Bread-making Test; Microscopic Examination
of Yeast; Testing Baking Powders for Alum; Testing
Baking Powders for Phosphoric Acid; Testing Baking
Powders for Ammonia; Vinegar Solids; Specific Gravity
of Vinegar; Acidity of Vinegar; Deportment of Vinegar
with Reagents; Testing Mustard for Turmeric; Examination
of Tea Leaves; Action of Iron Compounds upon
Tannic Acid; Identification of Coffee Berries; Detecting
Chicory in Coffee; Comparative Amounts of Soap Necessary
with Hard and Soft Water; Solvent Action of Water
on Lead; Suspended Matter in Water; Organic Matter
in Water; Deposition of Lime by Boiling Water; Qualitative
Tests for Minerals in Water; Testing for Nitrites
in Water.
REVIEW QUESTIONS 323
REFERENCES 350
INDEX 357
HUMAN FOODS AND THEIR NUTRITIVE VALUE
CHAPTER I
GENERAL COMPOSITION OF FOODS
1. Water.--All foods contain water. Vegetables in their natural
condition contain large amounts, often 95 per cent, while in meats there
is from 40 to 60 per cent or more. Prepared cereal products, as flour,
corn meal, and oatmeal, which are apparently dry, have from 7 to 14 per
cent. In general the amount of water in a food varies with the
mechanical structure and the conditions under which it has been
prepared, and is an important factor in estimating the value, as the
nutrients are often greatly decreased because of large amounts of water.
The water in substances as flour and meal is mechanically held in
combination with the fine particles and varies with the moisture
content, or hydroscopicity, of the air. Oftentimes foods gain or lose
water to such an extent as to affect their weight; for example, one
hundred pounds of flour containing 12 per cent of water may be reduced
in weight three pounds or more when stored in a dry place, or there may
be an increase in weight from being stored in a damp place. In tables
of analyses the results, unless otherwise stated, are usually given on
the basis of the original material, or the dry substance. Potatoes, for
example, contain 2-1/2 per cent of crude protein on the basis of 75 per
cent of water; or on a dry matter basis, that is, when the water is
entirely eliminated, there is 10 per cent of protein.
The water of foods is determined by drying the weighed material in a
water or air oven at a temperature of about 100° C, until all of the
moisture has been expelled in the form of steam, leaving the dry matter
or material free from water.[1] The determination of dry matter, while
theoretically a simple process, is attended with many difficulties.
Substances which contain much fat may undergo oxidation during drying;
volatile compounds, as essential oils, are expelled along with the
moisture; and other changes may occur affecting the accuracy of the
work. The last traces of moisture are removed with difficulty from a
substance, being mechanically retained by the particles with great
tenacity. When very accurate dry matter determinations are desired, the
substance is dried in a vacuum oven, or in a desiccator over sulphuric
acid, or in an atmosphere of some non-oxidizing gas, as hydrogen.
2. Dry Matter.--The dry matter of a food is a mechanical mixture of
the various compounds, as starch, sugar, fat, protein, cellulose, and
mineral matter, and is obtained by drying the material. Succulent
vegetable foods with 95 per cent of water contain only 5 per cent of
dry matter, while in flour with 12 per cent of water there is 88 per
cent, and in sugar 99 per cent. The dry matter is obtained by
subtracting the per cent of water from 100, and in foods it varies from
5 per cent and less in some vegetables to 99 per cent in sugar.
[Illustration: FIG. 1.--APPARATUS USED FOR THE DETERMINATION OF DRY
MATTER AND ASH IN FOODS.
1, desiccator; 2, muffle furnace for combustion of foods and obtaining
ash; 3, water oven for drying food materials.]
3. Ash.--The ash, or mineral matter, is that portion obtained by
burning or igniting the dry matter at the lowest temperature necessary
for complete combustion. The ash in vegetable foods ranges from 2 to 5
per cent and, together with the nitrogen, represents what was taken from
the soil during growth. In animal bodies, the ash is present mainly in
the bones, but there is also an appreciable amount, one per cent or
more, in all the tissues. Ash is exceedingly variable in composition,
being composed of the various salts of potassium, sodium, calcium,
magnesium, and iron, as sulphates, phosphates, chlorides, and silicates
of these elements. There are also other elements in small amounts. In
the plant economy these elements take an essential part and are
requisite for the formation of plant tissue and the production in the
leaves of the organic compounds which later are stored up in the seeds.
Some of the elements appear to be more necessary than others, and
whenever withheld plant growth is restricted. The elements most
essential for plant growth are potassium, calcium, magnesium, iron,
phosphorus, and sulphur.[1]
In the animal body minerals are derived, either directly or indirectly,
from the vegetable foods consumed. The part which each of the mineral
elements takes in animal nutrition is not well understood. Some of the
elements, as phosphorus and sulphur, are in organic combination with the
nitrogenous compounds, as the nucleated albuminoids, which are very
essential for animal life. In both plant and animal bodies, the mineral
matter is present as mineral salts and organic combinations. It is held
that the ash elements which are in organic combination are the forms
mainly utilized for tissue construction. While it is not known just what
part all the mineral elements take in animal nutrition, experiments show
that in all ordinary mixed rations the amount of the different mineral
elements is in excess of the demands of the body, and it is only in rare
instances, as in cases of restricted diet, or convalescence from some
disease, that special attention need be given to increasing the mineral
content of the ration. An excess of mineral matter in foods is equally
as objectionable as a scant amount, elimination of the excess entailing
additional work on the body.
The composition of the ash of different food materials varies widely,
both in amount, and form of the individual elements. When for any reason
it is necessary to increase the phosphates in a ration, milk and eggs do
this to a greater extent than almost any other foods. Common salt, or
sodium chloride, is one of the most essential of the mineral
constituents of the body. It is necessary for giving the blood its
normal composition, furnishing acid and basic constituents for the
production of the digestive fluids, and for the nutrition of the cells.
While salt is a necessary food, in large amounts, as when the attempt is
made to use sea water as a beverage, it acts as a poison, suggesting
that a material may be both a food and a poison. When sodium chloride is
entirely withheld from an animal, death from salt starvation ensues.
Many foods contain naturally small amounts of sodium chloride.
4. Organic Matter.--That portion of a food material which is converted
into gaseous or volatile products during combustion is called the
organic matter. It is a mechanical mixture of compounds made up of
carbon, hydrogen, oxygen, nitrogen, and sulphur, and is composed of
various individual organic compounds, as cellulose, starch, sugar,
albumin, and fat. The amount in a food is determined by subtracting the
ash and water from 100. The organic matter varies widely in composition;
in some foods it is largely starch, as in potatoes and rice, while in
others, as forage crops consumed by animals, cellulose predominates. The
nature of the prevailing organic compound, as sugar or starch,
determines the nutritive value of a food. Each has a definite chemical
composition capable of being expressed by a formula. Considered
collectively, the organic compounds are termed organic matter. When
burned, the organic compounds are converted into gases, the carbon
uniting with the oxygen of the air to form carbon dioxide, hydrogen to
form water, sulphur to form sulphur dioxide, and the nitrogen to form
oxides of nitrogen and ammonia.
5. Classification of Organic Compounds.--All food materials are
composed of a large number of organic compounds. For purposes of study
these are divided into classes. The element nitrogen is taken as the
basis of the division. Compounds which contain this element are called
nitrogenous, while those from which it is absent are called
non-nitrogenous.[2] The nitrogenous organic compounds are composed of
the elements nitrogen, hydrogen, carbon, oxygen, and sulphur, while the
non-nitrogenous compounds are composed of carbon, hydrogen, and oxygen.
In vegetable foods the non-nitrogenous compounds predominate, there
being usually from six to twelve parts of non-nitrogenous to every one
part of nitrogenous, while in animal foods the nitrogenous compounds are
present in larger amount.
NON-NITROGENOUS COMPOUNDS
6. Occurrence.--The non-nitrogenous compounds of foods consist mainly
of cellulose, starch, sugar, and fat. For purposes of study, they are
divided into subdivisions, as carbohydrates, pectose substances or
jellies, fats, organic acids, essential oils, and mixed compounds. In
plants the carbohydrates predominate, while in animal tissue the fats
are the chief non-nitrogenous constituents.
7. Carbohydrates.--This term is applied to a class of compounds
similar in general composition, but differing widely in structural
composition and physical properties. Carbohydrates make up the bulk of
vegetable foods and, except in milk, are found only in traces in animal
foods. They are all represented by the general formula CH_2n_2n, there
being twice as many hydrogen as oxygen atoms, the hydrogen and oxygen
being present in the same proportion as in water. As a class, the
carbohydrates are neutral bodies, and, when burned, form carbon dioxide
and water.
[Illustration: FIG. 2.--CELLULAR STRUCTURE OF PLANT CELL.]
8. Cellulose is the basis of the cell structure of plants, and is
found in various physical forms in food materials.[3] Sometimes it is
hard and dense, resisting digestive action and mechanically inclosing
other nutrients and thus preventing their being available as food. In
the earlier stages of plant growth a part of the cellulose is in
chemical combination with water, forming hydrated cellulose, a portion
of which undergoes digestion and produces heat and energy in the body.
Ordinarily, however, cellulose adds but little in the way of nutritive
value, although it is often beneficial mechanically and imparts bulk to
some foods otherwise too concentrated. The mechanical action of
cellulose on the digestion of food is discussed in Chapter XV.
Cellulose usually makes up a very small part of human food, less than 1
per cent. In refined white flour there is less than .05 of a per cent;
in oatmeal and cereal products from .5 to 1 per cent, depending upon the
extent to which the hulls are removed, and in vegetable foods from .1 to
1 per cent. The cellulose content of foods is included in the crude
fiber of the chemist's report.
9. Starch occurs widely distributed in nature, particularly in the
seeds, roots, and tubers of some plants. It is formed in the leaves of
plants as a result of the joint action of chlorophyll and protoplasm,
and is generally held by plant physiologists to be the first
carbohydrate produced in the plant cell. Starch is composed of a number
of overlapping layers separated by starch cellulose; between these
layers the true starch or amylose is found. Starch from the various
cereals and vegetables differs widely in mechanical structure; in wheat
it is circular, in corn somewhat angular, and in parsnips exceedingly
small, while potato starch granules are among the largest.[4] The nature
of starch can be determined largely from its mechanical structure as
studied under the microscope. It is insoluble in cold water because of
the protecting action of the cellular layer, but on being heated it
undergoes both mechanical and chemical changes; the grains are partially
ruptured by pressure due to the conversion into steam of the moisture
held mechanically. The cooking of foods is beneficial from a mechanical
point of view, as it results in partial disintegration of the starch
masses, changing the structure so that the starch is more readily acted
upon by the ferments of the digestive tract. At a temperature of about
120° C. starch begins to undergo chemical change, resulting in the
rearrangement of the atoms in the molecule with the production of
dextrine and soluble carbohydrates. Dextrine is formed on the crust of
bread, or whenever potatoes or starchy foods are browned. At a still
higher temperature starch is decomposed, with the liberation of water
and production of compounds of higher carbon content. When heated in
contact with water, it undergoes hydration changes; gelatinous-like
products are formed, which are finally converted into a soluble
condition. In cooking cereals, the hydration of the starch is one of the
main physical and chemical changes that takes place, and it simply
results in converting the material into such a form that other chemical
changes may more readily occur. Before starch becomes dextrose,
hydration is necessary. If this is accomplished by cooking, it saves the
body just so much energy in digestion. Many foods owe their value
largely to the starch. In cereals it is found to the extent of 72 to 76
per cent; in rice and potatoes in still larger amounts; and it is the
chief constituent of many vegetables. When starch is digested, it is
first changed to a soluble form and then gradually undergoes oxidation,
resulting in the production of heat and energy, the same
products--carbon dioxide and water--being formed as when starch is
burned. Starch is a valuable heat-producing nutrient; a pound yields
1860 calories. See Chapter XV.
10. Sugar.--Sugars are widely distributed in nature, being found
principally in the juices of the sugar cane, sugar beet, and sugar
maple. They are divided into two large classes: the sucrose group and
the dextrose group, the latter being produced from sucrose, starch, and
other carbohydrates by inversion and allied chemical changes. Because of
the importance of sugar in the dietary, Chapter V is devoted to the
subject.
11. Pectose Substances are jelly-like bodies found in fruits and
vegetables. They are closely related in chemical composition to the
carbohydrates, into which form they are changed during digestion; and in
nutrition they serve practically the same function. In the early stages
of growth the pectin bodies are combined with organic acids, forming
insoluble compounds, as the pectin in green apples. During the ripening
of fruit and the cooking of vegetables, the pectin is changed to a more
soluble and digestible condition. In food analysis, the pectin is
usually included with the carbohydrates.
12. Nitrogen-free-extract.--In discussing the composition of foods,
the carbohydrates other then cellulose, as starch, sugar, and pectin,
are grouped under the name of nitrogen-free-extract. Methods of
chemical analysis have not yet been sufficiently perfected to
enable accurate and rapid determination to be made of all these
individual carbohydrates, and hence they are grouped together as
nitrogen-free-extract. As the name indicates, they are compounds which
contain no nitrogen, and are extractives in the sense that they are
soluble in dilute acid and alkaline solutions. The nitrogen-free-extract
is determined indirectly, that is, by the method of difference. All the
other constituents of a food, as water, ash, crude fiber (cellulose),
crude protein, and ether extract, are determined; the total is
subtracted from 100, and the difference is nitrogen-free-extract. In
studying the nutritive value of foods, particular attention should be
given to the nature of the nitrogen-free-extract, as in some instances
it is composed of sugar and in others of starch, pectin, or pentosan
(gum sugars). While all these compounds have practically the same fuel
value, they differ in composition, structure, and the way in which they
are acted upon by chemicals and digestive ferments.[1]
[Illustration: FIG. 3.--APPARATUS USED FOR THE DETERMINATION OF
FAT.]
13. Fat.--Fat is found mainly in the seeds of plants, but to some
extent in the leaves and stems. It differs from starch in containing
more carbon and less oxygen. In starch there is about 44 per cent of
carbon, while in fat there is 75 per cent. Hence it is that when fat is
burned or undergoes combustion, it yields a larger amount of the
products of combustion--carbon dioxid and water--than does starch. A
gram of fat produces 2-1/4 times as much heat as a gram of starch. Fat
is the most concentrated non-nitrogenous nutrient. As found in food
materials, it is a mechanical mixture of various fats, among which are
stearin, palmitin, and olein. Stearin and palmitin are hard fats,
crystalline in structure, and with a high melting point, while olein is
a liquid. In addition to these three, there are also small amounts of
other fats, as butyrin in butter, which give character or individuality
to materials. There are a number of vegetable fats or oils which are
used for food purposes and, when properly prepared and refined, have a
high nutritive value. Occasionally one fat of cheaper origin but not
necessarily of lower nutritive value is substituted for another. The
fats have definite physical and chemical properties which enable them to
be readily distinguished, as iodine number, specific gravity, index of
refraction, and heat of combustion. By iodine number is meant the
percentage of iodine that will unite chemically with the fat. Wheat oil
has an iodine number of about 100, meaning that one pound of wheat oil
will unite chemically with one pound of iodine. Fats have a lower
specific gravity than water, usually ranging from .89 to .94, the
specific gravity of a fat being fairly constant. All fats can be
separated into glycerol and a fatty acid, glycerol or glycerine being
common constituents, while each fat yields its own characteristic acid,
as stearin, stearic acid; palmitin, palmitic acid; and olein, oleic
acid. The fats are soluble in ether, chloroform, and benzine. In the
chemical analysis of foods, they are separated with ether, and along
with the fat, variable amounts of other substances are extracted, these
extractive products usually being called "ether extract" or "crude
fat."[5] The ether extract of plant tissue contains in addition to fat
appreciable amounts of cellulose, gums, coloring, and other materials.
From cereal products the ether extract is largely fat, but in some
instances lecithin and other nitrogenous fatty substances are present,
while in animal food products, as milk and meat, the ether extract is
nearly pure fat.
14. Organic Acids.--Many vegetable foods contain small amounts of
organic acids, as malic acid found in apples, citric in lemons, and
tartaric in grapes. These give characteristic taste to foods, but have
no direct nutritive value. They do not yield heat and energy as do
starch, fat, and protein; they are, however, useful for imparting flavor
and palatability, and it is believed they promote to some extent the
digestion of foods with which they are combined by encouraging the
secretion of the digestive fluids. Many fruits and vegetables owe their
dietetic value to the organic acids which they contain. In plants they
are usually in chemical combination with the minerals, forming compounds
as salts, or with the organic compounds, producing materials as acid
proteins. In the plant economy they take an essential part in promoting
growth and aiding the plant to secure by osmotic action its mineral food
from the soil. Organic acids are found to some extent in animal foods,
as the various lactic acids of meat and milk. They are also formed in
food materials as the result of ferment action. When seeds germinate,
small amounts of carbohydrates are converted into organic acids. In
general the organic acids are not to be considered as nutrients, but as
food adjuncts, increasing palatability and promoting digestion.
15. Essential Oils.--Essential or volatile oils differ from fats, or
fixed oils, in chemical composition and physical properties.[6] The
essential oils are readily volatilized, leaving no permanent residue,
while the fixed fats are practically non-volatile. Various essential
oils are present in small amounts in nearly all vegetable food
materials, and the characteristic flavor of many fruits is due to them.
It is these compounds which are used for flavoring purposes, as
discussed in Chapter IV. The amount in a food material is very small,
usually only a few hundredths of a per cent. The essential oils have no
direct food value, but indirectly, like the organic acids, they assist
in promoting favorable digestive action, and are also valuable because
they impart a pleasant taste. Through poor methods of cooking and
preparation, the essential oils are readily lost from some foods.
16. Mixed Compounds.--Food materials frequently contain
compounds which do not naturally fall into the five groups
mentioned,--carbohydrates, pectose substances, fats, organic acids, and
essential oils. The amount of such compounds is small, and they are
classed as miscellaneous or mixed non-nitrogenous compounds. Some of
them may impart a negative value to the food, and there are others which
have all the characteristics, as far as general composition is
concerned, of the non-nitrogenous compounds, but contain nitrogen,
although as a secondary rather than an essential constituent.
17. Nutritive Value of Non-nitrogenous Compounds.--The non-nitrogenous
compounds, taken as a class, are incapable alone of sustaining life,
because they do not contain any nitrogen, and this is necessary for
producing proteid material in the animal body. They are valuable for
the production of heat and energy, and when associated with the
nitrogenous compounds, are capable of forming non-nitrogenous reserve
tissue. It is equally impossible to sustain life for any prolonged
period with the nitrogenous compounds alone. It is when these two
classes are properly blended and naturally united in food materials that
their main value is secured. For nutrition purposes they are mutually
related and dependent. Some food materials contain the nitrogenous and
non-nitrogenous compounds blended in such proportion as to enable one
food alone to practically sustain life, while in other cases it is
necessary, in order to secure the best results in the feeding of animals
and men, to combine different foods varying in their content of these
two classes of compounds.[7]
NITROGENOUS COMPOUNDS
18. General Composition.--The nitrogenous compounds are more complex
in composition than the non-nitrogenous. They are composed of a larger
number of elements, united in different ways so as to form a much more
complex molecular structure. Foods contain numerous nitrogenous organic
compounds, which, for purposes of study, are divided into four
divisions,--proteids, albuminoids, amids, and alkaloids. In addition to
these, there are other nitrogenous compounds which do not naturally fall
into any one of the four divisions.
[Illustration: FIG. 4.--APPARATUS USED FOR DETERMINING
TOTAL NITROGEN AND CRUDE PROTEIN IN FOODS.
The material is digested in the flask (3) with sulphuric acid and the
organic nitrogen converted into ammonium sulphate, which is later
liberated and distilled at 1, and the ammonia neutralized with standard
acid (2).]
Also in some foods there are small amounts of nitrogen in mineral forms,
as nitrates and nitrites.
19. Protein.--The term "protein" is applied to a large class of
nitrogenous compounds resembling each other in general composition, but
differing widely in structural composition. As a class, the proteins
contain about 16 per cent of nitrogen, 52 per cent of carbon, from 6 to
7 per cent of hydrogen, 22 per cent of oxygen, and less than 2 per cent
of sulphur. These elements are combined in a great variety of ways,
forming various groups or radicals. In studying the protein molecule a
large number of derivative products have been observed, as amid
radicals, various hydrocarbons, fatty acids, and carbohydrate-like
bodies.[8] It would appear that in the chemical composition of the
proteins there are all the constituents, or simpler products, of the
non-nitrogenous compounds, and these are in chemical combination with
amid radicals and nitrogen in various forms. The nitrogen of many
proteids appears to be present in more than one form or radical. The
proteids take an important part in life processes. They are found more
extensively in animal than in plant bodies. The protoplasm of both the
plant and animal cell is composed mainly of protein.
Proteids are divided into various subdivisions, as albumins, globulins,
albuminates, proteoses and peptones, and insoluble proteids. In plant
and animal foods a large amount of the protein is present as insoluble
proteids; that is, they are not dissolved by solvents, as water and
dilute salt solution. The albumins are soluble in water and coagulated
by heat at a temperature of 157° to 161° F. Whenever a food material is
soaked in water, the albumin is removed and can then be coagulated by
the action of heat, or of chemicals, as tannic acid, lead acetate, and
salts of mercury. The globulins are proteids extracted from food
materials by dilute salt solution after the removal of the albumins.
Globulins also are coagulated by heat and precipitated by chemicals. The
amount of globulins in vegetable foods is small. In animal foods myosin
in meat and vitellin, found in the yolk of the egg, and some of the
proteids of the blood, are examples of globulins. Albuminates are
casein-like proteids found in both animal and vegetable foods. They are
supposed to be proteins that are in feeble chemical combination with
acid and alkaline compounds, and they are sometimes called acid and
alkali proteids. Some are precipitated from their solutions by acids and
others by alkalies. Peas and beans contain quite large amounts of a
casein-like proteid called legumin. Proteoses and peptones are proteins
soluble in water, but not coagulated by heat. They are produced from
other proteids by ferment action during the digestion of food and the
germination of seeds, and are often due to the changes resulting from
the action of the natural ferments or enzymes inherent in the food
materials. As previously stated, the insoluble proteids are present in
far the largest amount of any of the nitrogenous materials of foods.
Lean meat and the gluten of wheat and other grains are examples of the
insoluble proteids. The various insoluble proteids from different food
materials each has its own composition and distinctive chemical and
physical properties, and from each a different class and percentage
amount of derivative products are obtained.[1] While in general it is
held that the various proteins have practically the same nutritive
value, it is possible that because differences in structural composition
and the products formed during digestion there may exist notable
differences in nutritive value. During digestion the insoluble proteids
undergo an extended series of chemical changes. They are partially
oxidized, and the nitrogenous portion of the molecule is eliminated
mainly in the form of amids, as urea. The insoluble proteins constitute
the main source of the nitrogenous food supply of both humans and
animals.
20. Crude Protein.--In the analysis of foods, the term "crude protein"
is used to designate the total nitrogenous compounds considered
collectively; it is composed largely of protein, but also includes the
amids, alkaloids, and albuminoids. "Crude protein" and "total
nitrogenous compounds" are practically synonymous terms. The various
proteins all contain about 16 per cent of nitrogen; that is, one part of
nitrogen is equivalent to 6.25 parts of protein. In analyzing a food
material, the total organic nitrogen is determined and the amount
multiplied by 6.25 to obtain the crude protein. In some food materials,
as cereals, the crude protein is largely pure protein, while in others,
as potatoes, it is less than half pure protein, the larger portion being
amids and other compounds. In comparing the crude protein content of one
food with that of another, the nature of both proteids should be
considered and also the amounts of non-proteid constituents. The factor
6.25 for calculating the protein equivalent of foods is not strictly
applicable to all foods. For example, the proteids of wheat--gliadin and
glutenin--contain over 18 per cent of nitrogen, making the nitrogen
factor about 5.68 instead of 6.25. If wheat contains 2 per cent of
nitrogen, it is equivalent to 12.5 per cent of crude protein, using the
factor 6.25; or to 11.4, using the factor 5.7. The nitrogen content of
foods is absolute; the protein content is only relative.[9]
21. Food Value of Protein.--Because of its complexity in composition,
protein is capable of being used by the body in a greater variety of
ways than starch, sugar, or fat. In addition to producing heat and
energy, protein serves the unique function of furnishing material for
the construction of new muscular tissue and the repair of that which is
worn out. It is distinctly a tissue-building nutrient. It also enters
into the composition of all the vital fluids of the body, as the blood,
chyme, chyle, and the various digestive fluids. Hence it is that protein
is required as a nutrient by the animal body, and it cannot be produced
from non-nitrogenous compounds. In vegetable bodies, the protein can be
produced synthetically from amids, which in turn are formed from
ammonium compounds. While protein is necessary in the ration, an
excessive amount should be avoided. When there is more than is needed
for functional purposes, it is used for heat and energy, and as foods
rich in protein are usually the most expensive, an excess adds
unnecessarily to the cost of the ration. Excess of protein in the ration
may also result in a diseased condition, due to imperfect elimination of
the protein residual products from the body.[10]
22. Albuminoids differ from proteids in general composition and, to
some extent, in nutritive value. They are found in animal bodies mainly
in the connective tissue and in the skin, hair, and nails. Some of the
albuminoids, as nuclein, are equal in food value to protein, while
others have a lower food value. In general, albuminoids are capable of
conserving the protein of the body, and hence are called "protein
sparers," but they cannot in every way enter into the composition of the
body, as do the true proteins.
23. Amids and Amines.--These are nitrogenous compounds of simpler
structure than the proteins and albuminoids. They are sometimes called
compound ammonia in that they are derived from ammonia by the
replacement of one of the hydrogen atoms with an organic radical. In
plants, amids are intermediate compounds in the production of the
proteids, and in some vegetables a large portion of the nitrogen is
amids. In animal bodies amids are formed during oxidation, digestion,
and disintegration of proteids. It is not definitely known whether or
not a protein in the animal body when broken down into amid form can
again be reconstructed into protein. The amids have a lower food value
than the proteids and albuminoids. It is generally held that, to a
certain extent, they are capable, when combined with proteids, of
preventing rapid conversion of the body proteid into soluble form. When
they are used in large amounts in a ration, they tend to hasten
oxidation rather than conservation of the proteids.
24. Alkaloids.--In some plant bodies there are small amounts of
nitrogenous compounds called alkaloids. They are not found to any
appreciable extent in food plants. The alkaloids, like ammonia, are
basic in character and unite with acids to form salts. Many medicinal
plants owe their value to the alkaloids which they contain. In animal
bodies alkaloids are formed when the tissue undergoes fermentation
changes, and also during disease, the products being known as ptomaines.
Alkaloids have no food value, but act physiologically as irritants on
the nerve centers, making them useful from a medicinal rather than from
a nutritive point of view. To medical and pharmaceutical students the
alkaloids form a very important group of compounds.
[Illustration: FIG. 5.--GRAPHIC COMPOSITION OF FLOUR.
1, flour; 2, starch; 3, gluten; 4, water; 5, fat; 6, ash.]
25. General Relationship of the Nitrogenous Compounds.--Among the
various subdivisions of the nitrogenous compounds there exists a
relationship similar to that among the non-nitrogenous compounds. From
proteids, amids and alkaloids may be formed, just as invert sugars and
their products are formed from sucrose. Although glucose products are
derived from sucrose, it is not possible to reverse the process and
obtain sucrose or cane sugar from starch. So it is with proteins, while
the amid may be obtained from the proteid in animal nutrition, as far
as known the process cannot be reversed and proteids be obtained from
amids. In the construction of the protein molecule of plants, nitrogen
is absorbed from the soil in soluble forms, as compounds of nitrates and
nitrites and ammonium salts. These are converted, first, into amids and
then into proteids. In the animal body just the reverse of this process
takes place,--the protein of the food undergoes a series of changes, and
is finally eliminated from the body as an amid, which in turn undergoes
oxidation and nitrification, and is converted into nitrites, nitrates,
and ammonium salts. These forms of nitrogen are then ready to begin
again in plant and animal bodies the same cycle of changes. Thus it is
that nitrogen may enter a number of times into the composition of plant
and animal tissues. Nature is very economical in her use of this
element.[5]
CHAPTER II
CHANGES IN COMPOSITION OF FOODS DURING COOKING AND PREPARATION
26. Raw and Cooked Foods Compared.--Raw and cooked foods differ in
chemical composition mainly in the content of water. The amount of
nutrients on a dry matter basis is practically the same, but the
structural composition is affected by cooking, and hence it is that a
food prepared for the table often differs appreciably from the raw
material. Cooked meat, for example, has not the same percentage and
structural composition as raw meat, although the difference in nutritive
value between a given weight of each is not large. During cooking, foods
are acted upon chemically, physically, and bacteriologically, and it is
usually the joint action of these three agencies that brings about the
desirable changes incident to their preparation for the table.
27. Chemical Changes during Cooking.--Each of the chemical compounds
of which foods are composed is influenced to a greater or less extent by
heat and modified in composition. The chemistry of cooking is mainly a
study of the chemical changes that take place when compounds, as
cellulose, starch, sugar, pectin, fat, and the various proteids, are
subjected to the joint action of heat, moisture, air, and ferments. The
changes which affect the cellulose are physical rather than chemical. A
slight hydration of the cellular tissue, however, does take place. In
human foods cellulose is not found to any appreciable extent. Many
vegetables, as potatoes, which are apparently composed of cellular
substances, contain but little true cellulose. Starch, as previously
stated, undergoes hydration in the presence of water, and, at a
temperature of 120° C., is converted into dextrine. At a higher
temperature disintegration of the starch molecule takes place, with the
formation of carbon monoxid, carbon dioxid, and water, and the
production of a residue richer in carbon than is starch. On account of
the moisture, the temperature in many cooking operations is not
sufficiently high for changes other than hydration and preliminary
dextrinizing. In Chapter XI is given a more extended account of the
changes affecting starch which occur in bread making.
During the cooking process sugars undergo inversion to a slight extent.
That is, sucrose is converted into levulose and dextrose sugars. At a
higher temperature, sugar is broken up into its constituents--water and
carbon dioxide. The organic acids which many fruits and vegetables
contain hasten the process of inversion. When sugar is subjected to dry
heat, it becomes a brown, caramel-like material sometimes called barley
sugar. During cooking, sugars are not altered in solubility or
digestibility; starches, however, are changed to a more soluble form,
and pectin--a jelly-like substance--is converted from a less to a more
soluble condition, as stated in Chapter I. Changes incident to the
cooking of fruits and vegetables rich in pectin, as in the making of
jellies, are similar to those which take place in the last stages of
ripening.
The fats are acted upon to a considerable extent by heat. Some of the
vegetable oils undergo slight oxidation, resulting in decreased
solubility in ether, but since there is no volatilization of the fatty
matter, it is a change that does not materially affect the total fuel
value of the food.[11]
There is a general tendency for the proteids to become less soluble by
the action of heat, particularly the albumins and globulins. The protein
molecule dissociates at a high temperature, with formation of volatile
products, and therefore foods rich in protein should not be subjected to
extreme heat, as losses of food value may result. During cooking,
proteids undergo hydration, which is necessary and preliminary to
digestion, and the heating need be carried only to this point, and not
to the splitting up of the molecule. Prolonged high temperature in the
cooking of proteids and starches is unnecessary in order to induce the
desired chemical changes. When these nutrients are hydrated, they are in
a condition to undergo digestion, without the body being compelled to
expend unnecessary energy in bringing about this preliminary change.
Hence it is that, while proper cooking does not materially affect the
total digestibility of proteids or starches, it influences ease of
digestion, as well as conserves available energy, thereby making more
economical use of these nutrients.
[Illustration: FIG. 6.--CELLS OF A PARTIALLY COOKED
POTATO. (After KÖNIG.)]
28. Physical Changes.--The mechanical structure of foods is influenced
by cooking to a greater extent than is the chemical composition. One of
the chief objects of cooking is to bring the food into better mechanical
condition for digestion.[12] Heat and water cause partial disintegration
of both animal and vegetable tissues. The cell-cementing materials are
weakened, and a softening of the tissues results. Often the action
extends still further in vegetable foods, resulting in disintegration of
the individual starch granules. When foods are subjected to dry heat,
the moisture they contain is converted into steam, which causes bursting
of the tissues. A good example of this is the popping of corn. Heat may
result, too, in mechanical removal of some of the nutrients, as the
fats, which are liquefied at temperatures ranging from 100° to 200° F.
Many foods which in the raw state contain quite large amounts of fat,
lose a portion mechanically during cooking, as is the case with bacon
when it is cut in thin slices and fried or baked until crisp. When foods
are boiled, the natural juices being of somewhat different density from
the water in which they are cooked, slight osmotic changes occur. There
is a tendency toward equalization of the composition of the juices of
the food and the water in which they are cooked. In order to achieve the
best mechanical effects in cooking, high temperatures are not necessary,
except at first for rupturing the tissues; softening of the tissues is
best effected by prolonged and slow heat. At a higher temperature many
of the volatile and essential oils are lost, while at lower temperatures
these are retained and in some instances slightly developed. The cooking
should be sufficiently prolonged and the temperature high enough to
effectually disintegrate and soften all of the tissues, but not to cause
extended chemical changes.
[Illustration: FIG. 7.--CELLS OF RAW POTATO, SHOWING STARCH
GRAINS. (After KÖNIG.)]
There is often an unnecessarily large amount of heat lost through faulty
construction of stoves and lack of judicious use of fuels, which greatly
enhances the cost of preparing foods. Ovens are frequently coated with
deposits of soot; this causes the heat to be thrown out into the room or
lost through the chimney, rather than utilized for heating the oven. In
an ordinary cook stove it is estimated that less than 7 per cent of the
heat and energy of the fuel is actually employed in bringing about
physical and chemical changes incident to cooking.[13]
29. Bacteriological Changes.--The bacterial organisms of foods are
destroyed in the cooking, provided a temperature of 150° F. is reached
and maintained for several minutes. The interior of foods rarely reaches
a temperature above 200° F., because of the water they contain which is
not completely removed below 212°. One of the chief objects in cooking
food is to render it sterile. Not only do bacteria become innocuous
through cooking, but various parasites, as trichina and tapeworm, are
destroyed, although some organisms can live at a comparatively high
temperature. Cooked foods are easily re-inoculated, in some cases more
readily than fresh foods, because they are in a more disintegrated
condition.
In many instances bacteria are of material assistance in the preparation
of foods, as in bread making, butter making, curing of cheese, and
ripening of meat. All the chemical compounds of which foods are
composed are subject to fermentation, each compound being acted upon by
its special ferment body. Those which convert the proteids into soluble
form, as the peptonizing ferments, have no action upon the
carbohydrates. A cycle of bacteriological changes often takes place in a
food material, one class of ferments working until their products
accumulate to such an extent as to prevent their further activity, and
then the process is taken up by others, as they find the conditions
favorable for development. This change of bacterial flora in food
materials is akin to the changes in the vegetation occupying soils. In
each case, there is a constant struggle for possession. Bacteria take a
much more important part in the preparation of foods than is generally
considered. As a result of their workings, various chemical products, as
organic acids and aromatic compounds, are produced. The organic acids
chemically unite with the nutrients of foods, changing their composition
and physical properties. Man is, to a great extent, dependent upon
bacterial action. Plant life also is dependent upon the bacterial
changes which take place in the soil and in the plant tissues. The
stirring of seeds into activity is apparently due to enzymes or soluble
ferments which are inherent in the seed. A study of the bacteriological
changes which foods undergo in their preparation and digestion more
properly belongs to the subject of bacteriology, and in this work only
brief mention is made of some of the more important parts which
microörganisms take in the preparation of foods.
30. Insoluble Ferments.--Insoluble ferments are minute, plant-like
bodies of definite form and structure, and can be studied only with the
microscope.[1] They are developed from spores or seeds, or from the
splitting or budding of the parent cells. Under suitable conditions they
multiply rapidly, deriving the energy for their life processes from the
chemical changes which they induce. For example, in the souring of milk
the milk sugar is changed by the lactic acid ferments into lactic acid.
In causing chemical changes, the ferment gives none of its own material
to the reacting substance. These ferment bodies undergo life processes
similar to plants of a higher order.
[Illustration: FIG. 8.--LACTIC ACID BACTERIA, MUCH
ENLARGED. (After RUSSELL.)]
All foods contain bacteria or ferments. In fact, it is impossible for a
food stored and prepared under ordinary conditions, unless it has been
specially treated, to be free from them. Some of them are useful, some
are injurious, while others are capable of producing disease. The
objectionable bacteria are usually destroyed by the joint action of
sunlight, pure air, and water.
31. Soluble Ferments.--Many plant and animal cells have the power of
secreting substances soluble in water and capable of producing
fermentation changes; to these the term "soluble ferments," or
"enzymes," is applied. These ferments have not a cell structure like
the organized ferments. When germinated seed, as malted barley, is
extracted, a soluble and highly nitrogenous substance, called the
diastase ferment, is secured that changes starch into soluble forms. The
soluble ferments induce chemical change by causing molecular disturbance
or splitting up of the organic compounds, resulting in the production of
derivative products. They take an important part in animal and plant
nutrition, as by their action insoluble compounds are brought into a
soluble condition so they can be utilized for nutritive purposes. In
many instances ferment changes are due to the joint action of soluble
and insoluble ferments. The insoluble ferment secretes an enzyme which
induces a chemical change, modified by the further action of the soluble
ferment. Many of the enzymes carry on their work at a low temperature,
as in the curing of meat and cheese in cold storage.[14]
32. General Relationship of Chemical, Physical, and Bacteriological
Changes.--It cannot be said that the beneficial results derived from
the cooking of foods are due to either chemical, physical, or
bacteriological change alone, but to the joint action of the three. In
order to secure a chemical change, a physical change must often precede,
and a bacteriological change cannot take place without causing a change
in chemical composition; the three are closely related and
interdependent.
33. Esthetic Value of Foods.--Foods should be not only of good
physical texture and contain the requisite nutrients, but they should
also be pleasing to the eye and served in the most attractive manner.
Some foods owe a part of their commercial value to color, and when they
are lacking in natural color they are not consumed with a relish. There
is no objection to the addition of coloring matter to foods, provided it
is of a non-injurious character and does not affect the amount of
nutrients, and that its presence and the kind of coloring material are
made known. Some foods contain objectionable colors which are eliminated
during the process of manufacture, as in the case of sugar and flour. As
far as removal of coloring matter from foods during refining is
concerned, there can be no objection, so long as no injurious reagents
or chemicals are retained, as the removal of the color in no way affects
the nutritive value or permits fraud, but necessitates higher
purification and refining. The use of chemicals and reagents in the
preparation and refining of foods is considered permissible in all cases
where the reagents are removed by subsequent processes. In the food
decisions of the United States Department of Agriculture, it is stated:
"Not excluded under this provision are substances properly used in the
preparation of food products for clarification or refining and
eliminated in the further process of manufacture." [15]
CHAPTER III
VEGETABLE FOODS
34. General Composition.--Vegetable foods, with the exception of
cereals, legumes, and nuts, contain a smaller percentage of protein than
animal food products. They vary widely in composition and nutritive
value; in some, starch predominates, while in others, sugar, cellulose,
and pectin bodies are most abundant. The general term "vegetable foods"
is used in this work to include roots, tubers, garden vegetables,
cereals, legumes, and all prepared foods of vegetable origin.
35. Potatoes contain about 75 per cent of water and 25 per cent of dry
matter, the larger portion being starch. There is but little nitrogenous
material in the potato, only 2.25 per cent, of which about half is in
the form of proteids. There are ten parts of non-nitrogenous substance
to every one part of nitrogenous; or, in other words, the potato has a
wide nutritive ratio, and as an article of diet needs to be supplemented
with foods rich in protein. The mineral matter, cellular tissue, and
fat in potatoes are small in amount, as are also the organic acids.
Mechanically considered, the potato is composed of three parts,--outer
skin, inner skin, and flesh. The layer immediately beneath the outer
skin is slightly colored, and is designated the fibro-vascular layer.
The outer and inner skins combined make up about 10 per cent of the
weight of the potato.
[Illustration: FIG. 9.--TRANSVERSE SECTION OF POTATO.
(After COWDEN and BUSSARD.) _a_, skin; _b_, cortical
layer; _c_, outer medullary layer; _d_, inner medullary layer.]
A large portion of the protein of the potato is albumin, which is
soluble in water. When potatoes are peeled, cut in small pieces, and
soaked in water for several hours before boiling, 80 per cent of the
crude protein, or total nitrogenous material, is extracted, rendering
the product less valuable as food. When potatoes are placed directly in
boiling water, the losses of nitrogenous compounds are reduced to about
7 per cent, and, when the skins are not removed, to 1 per cent.
Digestion experiments show that 92 per cent of the starch and 72 per
cent of the protein are digested.[12] Compared with other foods,
potatoes are often a cheap source of non-nitrogenous nutrients. If used
in excessive amounts, however, they have a tendency to make the ration
unbalanced and too bulky.
MECHANICAL COMPOSITION OF THE POTATO
================================================
|Per Cent
Unpeeled potatoes | 100.0
Outer, or true skin | 2.5
Inner skin, or fibro-vascular layer[A] | 8.5
Flesh | 89.0
================================================
CHEMICAL COMPOSITION OF THE POTATO
================================================================
| | | | CARBOHYDRATES
|-----|-------|---|------------------------
|Water| Crude |Fat|Nitrogen-free-| |
| |Protein| | extract |Fiber|Ash
| % | % | % | % | % |%
---------------------|-----|-------|---|--------------|-----|---
Outer, or true skin | 80.1| 2.7 |0.8| 14.|6 |1.8
Inner skin, or | | | | | |
fibro-vascular | | | | | |
layer | 83.2| 2.3 |0.1| 12.6 | 0.7 |1.1
Flesh | 81.1| 2.0 |0.1| 15.7 | 0.3 |0.8
Average of 86 | | | | | |
American analyses[B]| 78.0| 2.2 |0.1| 18.|8 |0.9
Average of 118 | | | | | |
European analyses[C]| 75.0| 2.1 |0.1| 21.0 | 0.7 |1.1
================================================================
[Footnote A: Including a small amount of flesh.]
[Footnote B: From an unpublished compilation of analyses of American
food products.]
[Footnote C: König, "Chemie der Nahrungs-und Genussmittel," 3d ed., II,
p. 626.]
36. Sweet Potatoes contain more dry matter than white potatoes, the
difference being due mainly to the presence of about 6 per cent of
sugar. There is approximately the same starch content, but more fat,
protein, and fiber. As a food, they supply a large amount of
non-nitrogenous nutrients.
37. Carrots contain about half as much dry matter as potatoes, and
half of the dry matter is sugar, nearly equally divided between sucrose
and levulose, or fruit sugar. Like the potato, carrots have some organic
acids and a relatively small amount of proteids. In carrots and milk
there is practically the same per cent of water. The nutrients in each,
however, differ both as to kind and proportion. Experiments with the
cooking of carrots show that if a large amount of water is used, 30 per
cent or more of the nutrients, particularly of the more soluble sugar
and albumin, are extracted and lost in the drain waters.[12] The color
of the carrot is due to the non-nitrogenous compound carrotin,
C_{26}H_{38}. Carrots are valuable in a ration not because of the
nutrients they supply, but for the palatability and the mechanical
action which the vegetable fiber exerts upon the process of digestion.
38. Parsnips contain more solid matter than beets or carrots, of which
3 to 4 per cent is starch. The starch grains are very small, being only
about one twentieth the size of the potato starch grains. There is 3 per
cent of sugar and an appreciable amount of fat, more than in any other
of the vegetables of this class, and seven times as much as in the
potato. The mineral matter is of somewhat different nature from that in
potatoes; in parsnips one half is potash and one quarter phosphoric
acid, while in potatoes three quarters are potash and one fifth
phosphoric acid.
39. Cabbage contains very little dry matter, usually less than 10 per
cent. It is proportionally richer in nitrogenous compounds than many
vegetables, as about two of the ten parts of dry matter are crude
protein, which makes the nutritive ratio one to five. During cooking 30
to 40 per cent of the nutrients are extracted. Cabbage imparts to the
ration bulk but comparatively little nutritive material. It is a
valuable food adjunct, particularly used raw, as in a salad, when it is
easily digested and retains all of the nutrients.[12]
[Illustration: FIG. 10.--GRAPHIC COMPOSITION OF CABBAGE.]
40. Cauliflower has much the same general composition as cabbage, from
which it differs mainly in mechanical structure.
41. Beets.--The garden beet contains a little more protein than
carrots, but otherwise has about the same general composition, and the
statements made in regard to the losses of nutrients in the cooking of
carrots and to their use in the dietary apply also to beets.
42. Cucumbers contain about 4 per cent of dry matter. The amount of
nutrients is so small as to scarcely allow them to be considered a food.
They are, however, a valuable food adjunct, as they impart palatability.
43. Lettuce contains about 7 per cent of solids, of which 1.5 is
protein and 2.5 starch and sugar. While low in nutrients, it is high in
dietetic value, because of the chlorophyll which it contains. It has
been suggested that it is valuable, too, for supplying iron in an
organic form, as there is iron chemically combined with the chlorophyll.
44. Onions are aromatic bulbs, valuable for condimental rather than
nutritive purposes. They contain essential and volatile oils, which
impart characteristic odor and flavor. In the onion there are about 1.5
per cent of protein and 9.5 per cent of non-nitrogenous material. Onions
are often useful in stimulating the digestive tract to action.
45. Spinach is a valuable food, not to be classed merely as a relish.
Its composition is interesting; for, although there is 90 per cent
water, and less than 10 per cent dry matter, it still possesses high
food value. Spinach contains 2.1 per cent crude protein, or about one
part to every four parts of carbohydrates. In potatoes, turnips, and
beets there are ten or more parts of carbohydrates to every one part of
protein.
46. Asparagus is composed largely of water, about 93 per cent. The dry
matter, however, is richer in protein than that of many vegetables.
Asparagus contains, too, an amid compound, asparagin, which gives some
of the characteristics to the vegetable.
47. Melons.--Melons contain from 8 to 10 per cent of dry matter, the
larger portion of which is sugar and allied carbohydrates. The flavor is
due to small amounts of essential oils and to organic acids associated
with the sugars. Melons possess condimental rather than nutritive value.
[Illustration: FIG. 11.--GRAPHIC COMPOSITION OF TOMATO.]
48. Tomatoes.--The tomato belongs to the night-shade family, and for
this reason was long looked upon with suspicion. It was first used for
ornamental purposes and was called "love-apple." Gradually, as the idea
of its poisonous nature became dispelled, it grew more and more popular
as a food, until now in the United States it is one of the most common
garden vegetables. It contains 7 per cent of dry matter, 4 per cent of
which is sucrose, dextrose, and levulose. It also contains some malic
acid, and a small amount of proteids, amids, cellulose, and coloring
material. In the canning of tomatoes, if too much of the juice is
excluded, a large part of the nutritive material is lost, as the sugars
and albumins are all soluble and readily removed.[16] If the seeds are
objectionable, they may be removed by straining and the juice added to
the fleshy portion. The product then has a higher nutritive value than
if the juice had been discarded with the seeds.
49. Sweet Corn.--Fresh, soft, green, sweet corn contains about 75 per
cent of water. The dry matter is half starch and one quarter sugar. The
protein content makes up nearly 5 per cent, a larger proportional amount
than is found in the ripened corn, due to the fact that the proteids are
deposited in the early stages of growth and the carbohydrates mainly in
the last stages. Sweet corn is a vegetable of high nutritive value and
palatability.
50. Eggplant contains a high per cent of water,--90 per cent. The
principal nutrients are starch and sugar, which make up about half the
weight of the dry matter. It does not itself supply a large amount of
nutrients, but the way in which it is prepared, by combination with
butter, bread crumbs, and eggs, makes it a nutritious and palatable
dish, the food value being derived mainly from the materials with which
it is combined, the eggplant giving the flavor and palatability.
51. Squash and Pumpkin.--Squash has much the same general composition
and food value as beets and carrots, although it belongs to a different
family. Pumpkins contain less dry matter than squash. The dry matter of
both is composed largely of starch and sugar and, like many other of the
vegetables, they are often combined with food materials containing a
large amount of nutrients, as in pumpkin and squash pies, where the food
value is derived mainly from the milk, sugar, eggs, flour, and butter or
other shortening used.
52. Celery.--The dry matter of celery is comparatively rich in
nitrogenous material, although the amount is small, and the larger
proportion is in non-proteid form. When grown on rich soil, celery may
contain an appreciable quantity of nitrates and nitrites, which have not
been converted into amids and proteids. The supposed medicinal value is
probably due to the nitrites which are generally present. Celery is
valuable from a dietetic rather than a nutritive point of view.
53. Sanitary Condition of Vegetables.--The conditions under which
vegetables are grown have much to do with their value, particularly from
a sanitary point of view. Uncooked vegetables often cause the spread of
diseases, particularly those, as cholera and typhoid, affecting the
digestive tract. Particles of dirt containing the disease-producing
organisms adhere to the uncooked vegetable and find their way into the
digestive tract, where the bacteria undergo incubation. When sewage has
been used for fertilizing the land, as in sewage irrigation, the
vegetables are unsound from a sanitary point of view. Such vegetables
should be thoroughly cleaned and also well cooked, in order to render
them sterile. Vegetables to be eaten in the raw state should be dipped
momentarily into boiling water, to destroy the activity of the germs
present upon the surface. They may then be immediately immersed in
ice-cold water, to preserve the crispness.
54. Miscellaneous Compounds in Vegetables.--In addition to the general
nutrients which have been discussed, many of the vegetables contain some
tannin, glucosides, and essential oils; and occasionally those grown
upon rich soils have appreciable amounts of nitrogen compounds, as
nitrates and nitrites, which have not been built up into proteids.
Vegetables have a unique value in the dietary, and while as a class they
contain small amounts of nutrients, they are indispensable for promoting
health and securing normal digestion of the food.
55. Canned Vegetables.--When sound vegetables are thoroughly cooked to
destroy ferments, and then sealed in cans while hot, they can be kept
for a long time without any material impairment of nutritive value.
During the cooking process there is lost a part of the essential oils,
which gives a slightly different flavor to the canned or tinned
goods.[17] In some canned vegetables preservatives are used, but the
enactment and enforcement of national and state laws have greatly
reduced their use. When the cans are made of a poor quality of tin, or
the vegetables are of high acidity, some of the metal is dissolved in
sufficient quantity to be objectionable from a sanitary point of
view.[18]
56. Edible Portion and Refuse of Vegetables.--Many vegetables have
appreciable amounts of refuse,[19] or non-edible parts, as skin, pods,
seeds, and pulp, and in determining the nutritive value, these must be
considered, as in some cases less than 50 per cent of the weight of the
material is edible portion, which proportionally increases the cost of
the nutrients. Ordinarily, the edible part is richer in protein than the
entire material as purchased. In some cases, however, the refuse is
richer in protein, but the protein is in a less available form. See
comparison of potatoes and potato skins.
CHAPTER IV
FRUITS, FLAVORS, AND EXTRACTS
57. General Composition.--Fruits are characterized by containing a
large amount of water and only a small amount of dry matter, which is
composed mainly of sugar and non-nitrogenous compounds. Fruits contain
but little fatty material and protein. A large portion of the total
nitrogen is in the form of amid compounds. Organic acids, as citric,
tartaric, and malic, are found in all fruits, and the essential oils
form a characteristic feature. The taste of fruits is due mainly to the
blending of the various organic acids, essential oils, and sugars.
Although fruits contain a high per cent of water, they are nevertheless
valuable as food.[20] The constituents present to the greatest extent
are sugars and acids. The sugar is not all like the common granulated
sugar, but in ripe fruits a part is in the form known as levulose or
fruit sugar, which is two and a half times sweeter than granulated
sugar. Sugars are valuable for heat-and fat-producing purposes, but not
for muscle repairing. Proteids are the muscle-forming nutrients. The
organic acids, as malic acid in apples, citric acid in lemons and
oranges, and tartaric acid in grapes, have characteristic medicinal
properties. The sugar, proteid, and acid content of some of our more
common fruits is given in the following table:[21]
COMPOSITION OF FRUITS
==============================================================
| WATER |PROTEIDS| SUGAR |ACID IN |KIND OF
| | | | JUICE | ACID
----------------|--------|--------|--------|--------|---------
|Per Cent|Per Cent|Per Cent|Per Cent|
Apples (Baldwin)| 85.0 | 0.50 | 10.75 | 0.92 |Malic
Apples, sweet | 86.0 | 0.50 | 11.75 | 0.20 |Malic
Blackberries | 88.9 | 0.90 | 11.50 | 0.75 |Malic
Currants | 86.0 | -- | 1.96 | 5.80 |Tartaric
Grapes | 83.0 | 1.50 |10 to 16|1.2 to 5|Tartaric
Strawberries | 90.8 | 0.95 | 5.36 | 1.40 |Malic
Oranges | 85.0 | 1.10 | 10.00 | 1.30 |Citric
Lemons | 84.0 | 0.95 | 2.00 | 7.20 |Citric
==============================================================
In addition to sugars, acids, and proteids, there are a great many other
compounds in fruits. Those which give the characteristic taste are
called essential or volatile oils.
58. Food Value.--When the nutrients alone are considered, fruits
appear to have a low food value, but they should not be judged entirely
on this basis, because they impart palatability and flavor to other
foods and exercise a favorable influence upon the digestive process. In
the human ration fruits are a necessary adjunct.
59. Apples.--Apples vary in composition with the variety and physical
characteristics of the fruit. In general they contain from 10 to 16 per
cent of dry matter, of which 75 per cent, or more, is sugar or allied
carbohydrates. Among the organic acids malic predominates, and the
acidity ranges from 0.1 to 0.8 per cent. Apples contain but little
protein, less than 1 per cent. There is some pectin, or jelly-like
substance closely related to the carbohydrates. The flavor of the apple
varies with the content of sugar, organic acids, and essential oils.
During storage some apples appear to undergo further ripening, resulting
in partial inversion of the sucrose, and there is a slight loss of
weight, due to the formation of carbon dioxide. The apple is an
important and valuable adjunct to the dietary.[22]
[Illustration: FIG. 12.--GRAPHIC COMPOSITION OF APPLE.]
[Illustration: FIG. 13.--GRAPHIC COMPOSITION OF ORANGE.]
60. Oranges contain nearly the same proportion of dry matter as
apples, the larger part of which is sugar. Citric acid predominates and
ranges in different varieties from 1 to 2.5 per cent. The amounts of
protein, fat, and cellulose are small. In some varieties of oranges
there is more iron and sulphur than is usually found in fruits. All
fruits, however, contain small amounts, but not as much as is found in
green vegetables. The average composition of oranges is as follows:
===========================================================
PHYSICAL COMPOSITION|CHEMICAL COMPOSITION OF EDIBLE PORTION
-----------------------------------------------------------
Per Cent| Per Cent
Rind 20 to 30| Solids 10 to 16
Pulp 25 to 35| Sugars 8 to 12
Juice 35 to 50| Citric acid 1 to 2.5
| Ash 0.5
===========================================================
61. Lemons differ from oranges in containing more citric acid and less
sucrose, levulose, and dextrose. The ash of the lemon is somewhat
similar in general composition to the ash of the orange, but is larger
in amount. The average composition of the lemon is as follows:
===========================================================
PHYSICAL COMPOSITION|CHEMICAL COMPOSITION OF EDIBLE PORTION
-----------------------------------------------------------
Per Cent| Per Cent
Rind 25 to 35| Solids 10 to 12
Pulp 25 to 35| Sugar 2 to 4
Juice 40 to 55| Citric acid 6 to 9
===========================================================
62. Grape Fruit.--The rind and seed of this fruit make up about 25 per
cent, leaving 75 per cent as edible portion. The juice contains 14 per
cent solids, of which nearly 10 per cent is sugar and 2.5 per cent is
citric acid. There is more acid in grape fruit than in oranges and
appreciably less than in lemons. The characteristic flavor is due to a
glucoside-like material. Otherwise the composition and food value are
about the same as of oranges.
[Illustration: FIG. 14.--GRAPHIC COMPOSITION OF STRAWBERRY.]
63. Strawberries contain from 8 to 12 per cent of dry matter, mainly
sugar and malic acid. The protein, fat, and ash usually make up less
than 2 per cent. Essential oils and coloring substances are present in
small amounts. It has been estimated that it would require 75 pounds of
strawberries to supply the protein for a daily ration. Nevertheless they
are valuable in the dietary. It has been suggested that the malic and
other acids have antiseptic properties which, added to the appearance
and palatability, make them a desirable food adjunct. Strawberries have
high dietetic rather than high food value.
64. Grapes contain more dry matter than apples or oranges. There is no
appreciable amount of protein or fat, and while they add some nutrients,
as sugar, to the ration, they do not contribute any quantity. Their
value, as in the case of other fruits, is due to palatability and
indirect effect upon the digestibility of other foods. In the juice of
grapes there is from 10 to 15 per cent or more of sugar, as sucrose,
levulose, and dextrose. Grapes contain also from 1 to 1.5 per cent of
tartaric acid, which, during the process of manufacture into wine, is
rendered insoluble by the alcohol formed, and the product, known as
argole, is used in the preparation of cream of tartar. Differences in
flavor and taste of grapes are due to variations in the sugar, acid, and
essential oil content.
65. Peaches contain about 12 per cent of dry matter, of which over 10
per cent is sugar and other carbohydrates. There is less than 1.5 per
cent of protein, fat, and mineral matter and about 0.5 per cent of acid.
The peach contains also a very small amount of hydrocyanic acid, which
is more liberally present in the kernel than in the fruit. Flavor is
imparted mainly by the sugar and essential oils. Peaches vary in
composition with variety and environment.[23]
66. Plums contain the most dry matter of any of the fruits, about 22
per cent, mainly sugar. About one per cent is acid and about 0.5 per
cent are protein and ash. There are a great many varieties of plums,
varying in composition. Dried plums (prunes) have mildly laxative
properties.
67. Olives.--The ripe olive contains about 15 per cent of oil,
exclusive of the pit, which makes up 20 per cent of the weight. In
green, preserved olives there is considerably less oil. Because of the
oil the olive has food value. Olive oil is slightly laxative and assists
mechanically in the digestion of foods.
68. Figs.--Dried figs contain about 50 per cent of sugar and 3.5 per
cent of protein. The fig has a mildly laxative action.
69. Dried Fruits.--Many fruits are prepared for market by drying. The
dried fruit has a slightly different composition from the fresh fruit
because of loss of the volatile and essential oils, and minor chemical
changes which take place during the drying process. When free from
preservatives, dried fruits are valuable adjuncts to the dietary and can
be advantageously used when fresh fruits are not obtainable.
70. Canning and Preservation of Fruits.--To obtain the best results in
canning, the fruit should not be overripe. After the ripened state has
been reached fermentation and bacterial changes occur, and it is more
difficult to preserve the fruit than when not so fully matured.[24] When
a fruit has begun to ferment, it is hard to destroy the ferment bodies
and their spores so as to prevent further ferment action. The chemical
changes that occur in the last stages of ripening are similar to those
which take place during the cooking process whereby the pectin or
jelly-like substances are rendered more soluble and digestible.
71. Adulterated Canned Fruits.--Analyses of a number of canned fruits,
made by various Boards of Health, show the presence of small amounts of
arsenic, tin, lead, and other poisonous metals. The quantity dissolved
depends upon the kind, age, and condition of the canned goods and the
state of the fruit when canned. The longer a can of fruit or vegetable
has been kept in stock, the larger is the amount of tin or metal that
has been dissolved. When fresh canned, there is usually very little
dissolved tin, but in old goods the amount may be comparatively large.
The tin used for the can is occasionally of poor quality and may contain
some arsenic, which also is dissolved. The occasional use of canned
goods preserved in tin is not objectionable, but they should not be used
continually if it can be avoided. Preservatives, as borax, salicylic
acid, benzoic acid, and sodium sulphate, are sometimes added to prevent
fermentation and to preserve the natural appearance of the fruit or
vegetable.[18]
72. Fruit Flavors and Extracts.--Formerly all fruit extracts and
flavors were obtained from vegetable sources; at present many are made
in the chemical laboratory by synthetic methods; that is, by combining
simpler organic compounds and radicals to produce the material having
the desired flavor and odor. The various fruit flavors are definite
chemical compounds, and can be produced in the laboratory as well as in
the cells of plants. When properly made, there is no difference in
chemical composition between the two. As prepared in the laboratory,
however, traces of acids, alkalies, and other compounds, used in
bringing about the necessary chemical combination, are often present,
not having been perfectly removed. Hence it is that natural and
artificial flavors differ mainly in the impurities which the artificial
flavors may contain.
Some of the flavoring materials have characteristic medicinal
properties, as the flavor of bitter almond, which contains hydrocyanic
acid, a poisonous substance. Flavors and extracts should not be
indiscriminately used. In small amounts they often exert a favorable
influence upon the digestion of foods, and the value of some fruits is
in a large measure due to the special flavors they contain. A study of
the separate compounds which impart flavor to fruits, as the various
aldehydes, ethers, and organic salts, belongs to organic chemistry
rather than to foods. Some of the simpler compounds of which flavors are
composed may exist in entirely different form or combination in food
products; as for example, pineapple flavoring is ethyl butrate. This can
be prepared by combination of butyric acid from stale butter with
alcohol which supplies the ethyl radical. The chemical union of the two
produces the new compound, ethyl butrate, the distinctive flavoring
substance of the pineapple. Banana flavor can be made from stale
butter, caustic soda, and chloroform. None of these materials, as such,
go into the flavor, but an essential radical is taken from each. These
manufactured products, when properly made, are in every essential
similar to the flavor made by the plant and stored up in the fruit. The
plant combines the material in the laboratory of the plant cell, and the
manufacturer of essences puts together these same constituents in a
chemical laboratory. In the fruit, however, the essential oil is
associated with a number of other compounds.
CHAPTER V
SUGARS, MOLASSES, SYRUP, HONEY, AND CONFECTIONS
73. Composition of Sugars.--The term "sugar" is applied to a large
class of compounds composed of the elements carbon, hydrogen, and
oxygen. Sugars used for household purposes are derived mainly from the
sugar cane and the sugar beet.[25] At the present time about two fifths
are obtained from the cane and about three fifths from the beet. When
subjected to the same degree of refining, there is no difference in the
chemical composition of the sugars from the two sources; they are alike
in every respect and the chemist is unable to determine their origin.
The production of sugar is an agricultural industry; the methods of
manufacture pertain more to industrial chemistry than to the chemistry
of foods, and therefore a discussion of them is omitted in this
work.[26]
[Illustration: FIG. 15.--SUGAR CRYSTALS.]
74. Commercial Grades of Sugar.--Sugars are graded according to the
size of the granule, the color and general appearance of the crystals,
and the per cent of sucrose or pure sugar. Common granulated sugar is
from 98.5 to 99.7 per cent pure sucrose. The impurities consist mainly
of moisture and mineral matter. In the process of refining, sulphur
fumes are frequently used for bleaching and clarifying the solution.[26]
The sulphurous acid formed is neutralized with lime, which is rendered
insoluble and practically all removed in subsequent filtrations. There
are, however, traces of sulphates and sulphites in ordinary sugar, but
these are in such small amounts as not to be injurious to health. When
sugar is burned, as in the bomb calorimeter, so as to permit collection
of all of the products of combustion, granulated sugar yields about 0.01
of a per cent of sulphur dioxid.[13] Occasionally coloring substances,
as a small amount of indigo, are added to yellow tinged sugars to impart
a white color, much on the same principle as the bluing of clothes. The
amount used is usually extremely small, and the effect on health has
never been determined. Occasionally, however, bluing is used to such an
extent that a blue scum appears when the sugar is boiled with water.
Sugar has high value for the production of heat and energy. Digestion
experiments show that when it is used in the dietary in not excessive
amounts, it is directly absorbed by the body and practically all
available. It can advantageously be combined with other foods to form a
part of the ration.[27] When a ration contains the requisite amount of
protein, sugar is used to the best advantage. Alone it is incapable of
sustaining life, because it does not contain any nitrogen. When sugar
was substituted for an excess of protein in a ration, it was found to
produce heat and energy at much less expense. Many foods, as apples,
grapes, and small fruits, contain appreciable amounts of sugar and owe
their food value almost entirely to their sugar content. In the dietary,
sugar is too frequently regarded as a condiment instead of a nutrient,
to be used for imparting palatability rather than for purposes of
nutrition. While valuable for improving the taste of foods, the main
worth of sugar is as a nutritive substance; used in the preparation of
foods it adds to the total heat and energy of the ration. Sugar is
sometimes used in excessive amounts and, as is the case with any food or
nutrient, when that occurs, nutrition disturbances result, due to misuse
of the food. Statistics show that the average consumption of sugar in
the United States is nearly 70 pounds a year per capita. In the dietary
of the adult, sugar to the extent of four ounces per day can be consumed
advantageously. The exclusion of sugar from the diet of children is a
great mistake, as they need it for heat and energy and to conserve the
protein for growth.
"Sugar is one of the most important forms in which carbohydrates
can be added to the diet of children. The great reduction in the
price of sugar which has taken place in recent years is probably
one of the causes of the improved physique of the rising
generation. The fear that sugar may injure children's teeth is,
largely illusory. The negroes who live largely on sugar cane have
the finest teeth the world can show. If injudiciously taken, sugar
may, however, injure the child's appetite and digestion. The
craving for sweets which children show is no doubt the natural
expression of a physiological need, but they should be taken with,
and not between, meals."[28]
[Illustration: FIG. 16.--NUTRIENTS OF A RATION WITH SUGAR.
The hacket parts represent the proportion of nutrients not digested.]
75. Sugar in the Dietary.--Sugar has an important place in the
dietary. It not only serves for the production of heat and energy in the
body, but is also valuable in enabling the proteids to be used more
economically. In reasonable amounts, it is particularly valuable in the
dietary of growing children, as the proteids of the food are then
utilized to better advantage for growth. The unique value of sugar
depends upon its intelligent use and its proper combination with other
foods, particularly with those rich in the nitrogenous compounds or
proteids. Sugar alone is incapable of sustaining life, but combined with
other foods is a valuable nutrient. The amount which can be
advantageously used depends largely upon the individual. Ordinarily
three to five ounces per day is sufficient, although some persons cannot
safely consume as much as this. In the case of diabetes mellitus, the
amount of sugar in the ration must be materially reduced. Persons in
normal health and engaged in outdoor work can use sugar to
advantage.[29] Many of the "harvest drinks," made largely from molasses
with a little ginger, and used extensively in some localities, are not
without merit, as they contain an appreciable amount of nutrients. Milk
contains more sugar as lactose or milk sugar than any other nutrient.
[Illustration: FIG. 17.--NUTRIENTS OF A RATION WITHOUT SUGAR.
The hacket parts represent the proportion of nutrients not digested.]
The craving for sugar by growing children and athletes is natural.
Sugar, however, is often injudiciously used, and a perverted taste may
be established which can be satisfied only by excessive amounts. This
results in impaired digestion and malnutrition.
76. Maple Sugar.--Sugar obtained by evaporation from the sap of the
maple tree (_Acer saccharinum_) is identical, except for the foreign
substances which it contains, with that from the beet and sugar cane.
The mottled appearance and characteristic color and taste of maple sugar
are due to the various organic acids and other compounds present in the
maple sap and recovered in the sugar. Maple sugar, as ordinarily
prepared, has 0.4 of a per cent or more of ash or mineral matter, while
refined cane sugar contains less than one tenth as much.[30] Hence, when
maple sugar is adulterated with cane and beet sugars, the ash content is
noticeably lowered, as is also the content of organic acids. It is
difficult, however, to determine with absolute certainty pure high grade
maple sugar from the impure low grade to which a small amount of
granulated sugar has been added.
77. Adulteration of Sugar.--Sugar at the present time is not
materially adulterated. Other than the substances mentioned which are
used for clarification and color, none are added during refining which
remain in the sugar in appreciable amounts. Sugar does not readily lend
itself to adulteration, as it has a definite crystalline structure, and
materials that would be suitable for its adulteration are of entirely
different physical character.[31] Cane sugar is not easily blended with
glucose, or starch sugar, because of the physical differences between
the two. The question of the kind of sugar to use in the household, as
granulated, loaf, or pulverized, is largely one of personal choice, as
there is no appreciable difference in the nutritive value or purity of
the different kinds.
78. Dextrose Sugars.--Products known as glucose and dextrose sugars
are made from corn and other starches; they can also be prepared from
cane sugar by the use of heat, chemicals, or ferments for carrying on
the process known as inversion. The dextrose sugars differ from cane
sugar in containing a dissimilar number of carbon, hydrogen, and oxygen
atoms in the molecule. The formula of the dextrose sugars is
C_{6}H_{12}_O{6}, while that of cane sugar is C_{12}H_{22}O_{11}. By the
addition of one molecule of water, H_{2}O, to a molecule of sucrose, two
molecules of invert sugar (dextrose and glucose) are produced:[1]
C_{12}H_{22}O_{11} + H_{2} = C_{6}H_{12}O_{6} + C_{6}H_{12}O_{6}. In
bringing about this change, acids are employed, but the acid in no way
enters into the chemical composition of the final product; it is removed
as described during the process of sugar manufacture. The action of the
acid brings about a catalytic change, the acid being necessary only as a
presence reagent to start the chemical reaction. When properly prepared
and the acid product thoroughly removed, dextrose and glucose have
practically the same food value as sugar. When they are digested, heat
and energy are produced, and a given weight has about the same fuel
value as an equal weight of sugar. Some of the glucose-yielding products
can be made at less expense than sugar, and when they are sold under
their right names there is no reason why they should not be used in the
dietary, as they serve the same nutritive purpose.
79. Molasses is a by-product obtained in the refining of sugar. It is
a mixture of cane sugar and invert sugars, as levulose and dextrose.
When in sugar making the sucrose is removed by crystallization, a point
is finally reached where the solution, or mother liquid, as it is
called, refuses to give up any further crystals;[31] then this product,
consisting of various sugars and small amounts of organic acids and ash,
is partially refined and clarified to form molasses. The term "New
Orleans" molasses was formerly applied to the product obtained by the
use of open kettles for the manufacture of sugar, but during recent
years the vacuum pan process has been introduced, and "New Orleans"
molasses is now an entirely different article. The terms first, second,
and third molasses are applied to the liquids obtained after the removal
of the first, second, and third crops of sugar crystals; first molasses
being richer in sucrose, while third molasses is richer in dextrose and
invert sugars. The ash in molasses ranges from 4 to 6.5 per cent. Some
of the low grades of molasses are used in the preparation of animal
foods.
The taste and physical characteristics of molasses are due largely to
the organic acids and impurities that are present, as well as to the
proportion in which the various sugars occur. When used with soda in
cooking and baking operations, the organic acid of the molasses
liberates carbon dioxide gas, which acts as a leavening agent. Because
of the organic acids, molasses should not be stored in tin or metalware
dishes, as the solvent action results in producing poisonous tin and
other metallic salts.
The food value of molasses is dependent entirely upon the amount of dry
matter and the per cent of sugar. A large amount of water is considered
an adulterant; ordinarily molasses contains from 20 to 33 per cent. If a
sample of molasses contains 75 per cent of dry matter, it has slightly
less than three fourths of the nutritive value of the same weight of
sugar.
80. Syrups.--The term "syrup" is applied to natural products obtained
by evaporation and purification of the saccharine juices of plants.
Sorghum syrup is from the sorghum plant, which is pressed by machinery
and the juice clarified and evaporated so as to contain about 25 per
cent of water. In sorghum syrups there are from 30 to 45 per cent of
cane sugar, and from 12 to 20 per cent of glucose and invert sugars.
Cane syrup is made from the clarified juice of the sugar cane, and has
about the same general composition as sorghum syrup. Maple syrup,
prepared from the juice of the sugar maple, is characteristically rich
in sucrose and contains but little glucose or reducing sugars. The
flavor of all the syrups is due mainly to organic acids, ethereal
products, and impurities. In some instances the essential flavor can be
produced synthetically, or derived from other and cheaper materials;
and by the use of these flavors, mixed syrups can be prepared closely
resembling many of the natural products. When properly made, they are
equal in nutritive value to natural syrups. When sold under assumed
names, they are to be considered and classified as adulterated, and not
as syrups from definite and specific products. Low-grade syrups and
molasses are often used for making fuel alcohol. They readily undergo
alcoholic fermentation and are valuable for this purpose, rendering it
possible for a good grade of fuel alcohol to be produced at low cost.
The manufacture of sugar, syrups, and molasses has been brought to a
high degree of perfection through the assistance rendered by industrial
chemistry. Losses in the process are reduced to a minimum, and the
various steps are all controlled by chemical analysis. Sugar has the
physical property of deflecting a ray of polarized light, the amount of
deflection depending upon the quantity of sugar in solution. This is
measured by the polariscope, an instrument by means of which the sugar
content of sugar plants is rapidly determined.
[Illustration: FIG. 18.--GRAPHIC COMPOSITION OF
SYRUP.]
81. Honey is composed largely of invert sugars gathered by the
honeybee from the nectar of flowers. It varies in composition and flavor
according to its source. The color depends upon the flower from which it
came, white clover giving a light-colored, pleasant-flavored honey,
while that from buckwheat and goldenrod is dark and has a slightly rank
taste. The comb is composed largely of wax, which has somewhat the same
general composition as fat, but contains ethereal instead of glycerol
bodies. On account of the predominance of invert sugars, pure honey has
a levulo or left-handed rotation when examined by the polariscope. Honey
contains from 60 to 75 per cent of invert sugars, and from 12 to 20 per
cent of water, while the ash content is small, less than one tenth of
one per cent. Strained honey is easily adulterated with glucose
products. Adulteration with cane sugar is readily detected, as pure
honey contains only a very small amount of sucrose. Honey can be made by
feeding bees on sugar; the sugar undergoes inversion, with the
production of dextrose. Such honey, although not adulterated, is
inferior in quality and lacking in natural flavor.[18]
82. Confections.--By blending various saccharine products, confections
are made. Usually sucrose (cane and beet sugar) is used as the basis for
their preparation. Sucrose has definite physical properties, as
crystalline structure, and forms chemical and mechanical combinations
with acid, alkaline, and other substances; it also unites with water,
and when heated undergoes changes in structural composition. The
presence of small amounts of acid substances, or variations in the
concentration of the sugar solution, materially affect the mechanical
relation of the sugar particles to each other, and their
crystallization. Usually crystallization takes place when there is less
than 25 per cent of water present. The form, size, and arrangement of
the crystals are influenced by agitation during cooling. To secure
desired results, often small quantities of various other substances are
employed for their mechanical action. Glucose is frequently used, and is
said to be necessary for the production of some kinds of candy.
Candies are colored with various dyes and pigments, many of which are
harmless, although some are injurious. Coal tar dyes are frequently
employed for this purpose. Objection has generally been urged against
their use, as it is believed many of them are injurious to health. It
cannot be said, however, that all are poisonous, as some are known to be
harmless. The use of a few coal tar dyes is allowed by the United States
government. Mineral colors are now rarely, if ever, used.
Impure candies result from objectionable ingredients, as starch,
paraffin, and large amounts of injurious coloring substances. Coal tar
coloring materials are identified in the way described in Experiment No.
13. Confectionery, when properly prepared and unadulterated, has the
same nutritive value as sugar and the other ingredients, and is entitled
to a place in the dietary for the production of heat and energy. Much
larger amounts of candies are sold and consumed during the winter than
the summer months, suggesting that in cold weather candy is most needed
in the dietary.
83. Saccharine is an artificial sweetening, five hundred times sweeter
than cane sugar. It contains in its molecule, chemically united,
benzine, sulphuric acid, and ammonia radicals. It is employed for
sweetening purposes in cases of diabetes mellitus, where physicians
advise against the use of sugar. It has no food value. A small amount is
sometimes added to canned corn and tomatoes to impart a sweet taste. The
physiological properties of saccharine have not been extensively
investigated.
CHAPTER VI
LEGUMES AND NUTS
84. General Composition of Legumes.--Peas, beans, lentils, and peanuts
are the legumes most generally used for human food. As a class, they are
characterized by high protein content and a comparatively low per cent
of starch and carbohydrates. They contain the largest amount of
nitrogenous compounds of any of the vegetable foods, and hence are
particularly valuable in the human ration as a substitute for meats.[32]
For feeding animals the legumes are highly prized, particularly the
forage crops, clover and alfalfa. These secure their nitrogen, which is
the characteristic element of protein, from the free nitrogen of the
air, through the workings of bacterial organisms found in the nodules on
the roots of the plants. The legumes appear to be the only plants
capable of making use of the nitrogen of the air for food purposes.
85. Beans contain about 24 per cent of protein and but little fat,
less than is found in any of the grain or cereal products. The protein
of the bean differs from that of cereals in its general and structural
composition. It is a globulin known as legumin, and is acted upon
mainly by ferments working in alkaline solutions, as in the lower part
of the digestive tract. Beans have about the same amount of ash as the
cereals, but the ash is richer in potash and lime.
[Illustration: FIG. 19.--GRAPHIC COMPOSITION OF BEANS.
HACKED PART INDIGESTIBLE.]
86. Digestibility of Beans.--Beans are usually considered
indigestible, but experiments show they are quite completely digested,
although they require more work on the part of the digestive tract than
many other foods. The digestibility was found to vary with individuals,
86 per cent of the protein being digested in one case, and only 72 per
cent in another. The protein of beans is not as completely digested as
that of meats. When beans were combined with other foods, forming a part
of a ration, they were more completely digested than when used in large
amounts and with only a few other foods. The presence of the skin is in
part responsible for low digestibility. When in the preparation of beans
the skins, which contain a large amount of cellulose, are removed, the
beans are more completely digested. By cooking from twenty minutes to
half an hour in rapidly boiling water containing a small amount of soda,
the skins are softened and loosened and are then easily removed by
rubbing in cold water. Some of the soda enters into combination with the
legumin. Along with the skins a portion of the germ is lost. The germ
readily ferments, which is probably the cause of beans producing
flatulence with some individuals during digestion. After the skins are
removed the nutrients are more susceptible to the action of the
digestive fluids. Experiments show that 42 per cent of the protein of
baked skinned beans is soluble in pepsin and pancreatin solutions, while
under similar conditions there is only 3.85 per cent of the protein
soluble from beans baked without removal of the skins.
[Illustration: FIG. 20.--BEANS, RAW AND COOKED. SKINS, WET
AND DRY.]
87. Use of Beans in the Dietary.--There is no vegetable food capable
of furnishing so much protein at such low cost as beans; from a pound
costing five cents about one fifth of a pound of protein and three
fifths of a pound of carbohydrates are obtained. Beans can, to a great
extent, take the place of meats in the dietary. There is more protein in
beans than in beef. Four ounces of uncooked beans or six ounces of baked
beans are as much as can conveniently be combined in the dietary, and
these will furnish a quarter of the protein of the ration. In the case
of active out-of-door laborers over a pound of baked beans per day is
often consumed with impunity.
88. String Beans.--String beans--green beans with pod--contain a large
amount of water, 85 to 88 per cent. The dry matter is rich in protein,
nearly 20 per cent, although in the green beans as eaten, containing 85
per cent water, there is less than 2-1/2 per cent. Lima beans are richer
in protein than string beans, as the green pod is not included. String
beans are valuable both for the nutrients they contain and for the
favorable influence they exert upon the digestibility of other foods.
89. Peas.--In general composition and digestibility, peas are quite
similar to beans. They belong to the same family, Leguminosæ, and the
protein of each is similar in quantity and general properties. The
statements made in regard to the composition, digestibility, and use of
beans in the dietary apply with minor modifications to peas. When used
in the preparation of soups, they add appreciable amounts of nutrients.
[Illustration: FIG. 21.--PEA STARCH GRANULES.]
90. Canned Peas.--In order to impart a rich green color, copper
sulphate has been used in the canning of peas. Physiologists differ as
to its effect upon health. While a little may not be particularly
injurious, much interferes with normal digestion of the food and forms
insoluble copper proteids. In some countries a small amount of copper
sulphate is tolerated, while in others it is prohibited.
91. Peanuts.--Peanuts differ from peas and beans in containing more
fat. They should be considered a food, for at ordinary prices they
furnish a large amount of protein and fat. Like the other members of the
legume family, the peanut is rather slow of digestion and requires
considerable intestinal work for completion of the process.
NUTS
92. General Composition.--Nuts should be regarded as food, for they
contribute to a ration appreciable amounts of nutrients. The edible
portion of nearly all is rich in fat; pecans, for example, contain as
high as 70 per cent. In protein content nuts range from 3 per cent in
cocoanuts to 30 per cent in peanuts. The carbohydrate content is usually
comparatively low, less than 5 per cent in hickory nuts, although there
is nearly 40 per cent in chestnuts. On account of high fat content, nuts
supply a large amount of heat and energy.[33]
93. Chestnuts are characterized by containing less fat and protein and
much more carbohydrate material, especially starch, than is found in
other nuts. In southern Europe chestnuts are widely used as food; the
skins are removed, and the nuts are steamed, boiled, or roasted, and
sometimes they are dried and ground into flour. Chestnuts are less
concentrated in protein and fat, and form a better balanced food used
alone than do other nuts.
94. The Hickory Nut, which is a characteristically American nut,
contains in the edible portion about 15 per cent protein, 65 per cent
fat, and 12 per cent carbohydrates.
95. The Almonds used in the United States come chiefly from southern
Europe, although they are successfully raised in California. They
contain about 55 per cent fat and 22 per cent protein. The flavor of
almonds is due to a small amount of hydrocyanic acid.
96. Pistachio.--Some nuts are used for imparting color and flavor to
food products, as the pistachio nut, the kernel of which is greenish in
color and imparts a flavor suggestive of almonds. The pistachio has high
food value, as it is rich in both fat and protein. It is employed in the
manufacture of confectionery and in ice cream for imparting flavor and
color.
97. Cocoanuts grow luxuriantly in many tropical countries, and have a
high food value. They are characteristically rich in fat, one half of
the edible portion being composed of this nutrient. For tropical
countries they supply the fat of a ration at less expense than any other
food. When used in large amounts they should be supplemented with foods
rich in carbohydrates, as rice, and in proteids, as beans. Cocoanut milk
is proportionally richer in carbohydrates and poorer in fat and protein
than the meat of the cocoanut. In discussing the cocoanut, Woods
states:[34]
"The small, green, and immature nuts are grated fine for medicinal
use, and when mixed with the oil of the ripe nut it becomes a
healing ointment. The jelly which lines the shell of the more
mature nut furnishes a delicate and nutritious food. The milk in
its center, when iced, is a most delicious luxury. Grated cocoanut
forms a part of the world-renowned East India condiment, curry.
Dried, shredded (desiccated) cocoanut is an important article of
commerce. From the oil a butter is made, of a clear, whitish color,
so rich in fat, that of water and foreign substances combined there
are but O.0068. It is better adapted for cooking than for table
use. At present it is chiefly used in hospitals, but it is rapidly
finding its way to the tables of the poor, particularly as a
substitute for oleomargarine."
98. Use of Nuts in the Dietary.--When nuts can be secured at a low
price per pound, ten cents or less, they compare favorably in nutritive
value with other staple foods. Digestion experiments with rations
composed largely of nuts show that they are quite thoroughly digested.
Professor Jaffa of the California Experiment Station, in discussing the
nutritive value of nuts and fruits, says:[35]
"It is certainly an error to consider nuts merely as an accessory
to an already heavy meal, and to regard fruit merely as something
of value for its pleasant flavor, or for its hygienic or medicinal
virtues. The agreement of one food or another with any person is
more or less a personal idiosyncrasy, but it seems fair to say that
those with whom nuts and fruits agree, can, if they desire, readily
secure a considerable part of their nutritive material from such
sources."
AVERAGE COMPOSITION OF NUTS
(From Fifteenth Annual Report, Maine Agricultural Experiment Station.)
===========================================================================
|REFUSE|EDIBLE | EDIBLE PORTION |VALUE[A]
| | |------------------------------|
| |PORTION|Water|Prot.| Fat |Carb.| Ash | PER LB.
---------------------------------------------------------------------------
| % | % | % | % | % | % | % |Calories
Almonds | 64.8 | 35.2 | 1.7 | 7.3 |19.3 | 6.2 | 0.7 | 1065
Almonds, kernels | -- | 100.0 | 4.8 |21.0 |54.9 |17.3 | 2.0 | 3030
Brazil nuts | 49.6 | 50.4 | 2.7 | 8.6 |33.6 | 3.5 | 2.0 | 1545
Filberts | 52.1 | 47.9 | 1.8 | 7.5 |31.3 | 6.2 | 1.1 | 1575
Filberts, kernels | -- | 100.0 | 3.7 |15.6 |65.3 |13.0 | 2.4 | 3290
Hickory nuts | 62.2 | 37.8 | 1.4 | 5.8 |25.5 | 4.3 | 0.8 | 1265
Pecans | 49.7 | 50.3 | 1.4 | 5.2 |35.6 | 7.2 | 0.8 | 1733
Pecans, kernels | -- | 100.0 | 2.9 |10.3 |70.8 |14.3 | 1.7 | 3445
Walnuts | 58.0 | 42.0 | 1.2 | 7.0 |27.0 | 6.1 | 0.7 | 1385
Walnuts, kernels | -- | 100.0 | 2.8 |16.7 |64.4 |14.8 | 1.3 | 3305
Chestnuts | 16.1 | 83.9 |31.0 | 5.7 | 6.7 |39.0 | 1.5 | 1115
Acorns | 35.6 | 64.4 | 2.6 | 5.2 |24.1 |30.9 | 1.6 | 1690
Beechnuts | 40.8 | 59.2 | 2.3 |13.0 |34.0 | 7.8 | 2.1 | 1820
Butternuts | 86.4 | 13.6 | 0.6 | 3.8 | 8.3 | 0.5 | 0.4 | 430
Litchi nuts | 41.6 | 58.4 |10.5 | 1.7 | 0.1 |45.2 | 0.9 | 875
Piñon, P. edulis | 40.6 | 59.4 | 2.0 | 8.7 |36.8 |10.2 | 1.7 | 1905
Piñon, P. monophylla| 41.7 | 58.3 | 2.2 | 3.8 |35.4 |15.3 | 1.6 | 1850
Piñon, P. sabiniana | 77.0 | 23.0 | 1.2 | 6.5 |12.3 | 1.9 | 1.1 | 675
Pistachio, kernels | -- | 100.0 | 4.2 |22.6 |54.5 |15.6 | 3.1 | 3010
Peanuts, raw | 26.4 | 73.6 | 6.9 |20.6 |30.7 |13.8 | 1.6 | 1935
Peanuts, kernels | -- | 100.0 | 9.3 |27.9 |42.0 |18.7 | 2.1 | 2640
Roasted peanuts | 32.6 | 67.4 | 1.1 |20.6 |33.1 |10.9 | 1.7 | 1985
Shelled peanuts | -- | 100.0 | 1.6 |30.5 |49.2 |16.2 | 2.5 | 2955
Peanut butter | -- | -- | 2.0 |29.3 |46.6 |17.1 |[B]5.0| 2830
Cocoanuts | 48.8 | 51.2 | 7.2 | 2.9 |25.9 |14.3 | 0.9 | 1415
Cocoanuts, shredded | -- | -- | 3.5 | 6.3 |57.3 |31.6 | 1.3 | 3125
Cocoanut milk | -- | -- |92.7 | 0.4 | 1.5 | 4.6 | 0.8 | 97
=========================================================================
[Footnote A: Calculated from analyses.]
[Footnote B: Including salt, 4.1.]
CHAPTER VII
MILK AND DAIRY PRODUCTS
99. Importance in the Dietary.--There is no article of food which
enters so extensively into the dietary as milk, and it is one of the few
foods which supply all the nutrients,--fats, carbohydrates, and
proteids.[36] Milk alone is capable of sustaining life for comparatively
long periods, and it is the chief article of food during many diseases.
An exclusive milk diet for a healthy adult, however, would be
unsatisfactory; in the case of young children, milk is essential,
because the digestive tract has not become functionally developed for
the digestion of other foods.
It is necessary to consider not only the composition and nutritive value
of milk, but also its purity or sanitary condition.
100. General Composition.--Average milk contains about 87 per cent
water and 13 per cent dry matter. The dry matter is composed
approximately of:
=======================
| Per Cent
Fat | 3.5
Casein | 3.25
Albumin | 0.50
Milk sugar | 5.00
Ash | 0.75
=======================
[Illustration: FIG. 22.--MILK FAT GLOBULES.]
Fat is the most variable constituent of milk. Occasionally it is found
as low as 2 per cent and as high as 6 per cent or more. The poorest and
richest milks differ mainly in fat content, as the sugar, ash, casein,
and albumin, or "solids of the milk serum," are fairly constant in
amount and composition. Variations in the content of fat are due to
differences in feed and in the breed and individuality of the animal.
101. Digestibility.--Milk is one of the most completely digested of
foods, about 95 per cent of the protein and fat and 97 per cent of the
carbohydrates being absorbed and utilized by the body.
In a mixed ration, the nutrients of milk are practically all absorbed.
Milk also exerts a favorable influence upon the digestibility of other
foods with which it is combined. This is doubtless due to the digestive
action of the special ferments or enzymes which milk contains. In milk
there is a soluble ferment material or enzyme which has the power of
peptonizing proteids. It is this ferment which carries on the ripening
process when cheese is cured in cold storage, and it is believed to be
this body which promotes digestion of other foods with which milk is
combined.[27]
Milk is not easily digested by some persons. The tendency to costiveness
caused by a milk diet can be largely overcome by the use of salt with
the milk, or of some solid food, as toast or crackers, to prevent
coagulation and the formation of masses resistant to the digestive
fluids. Barley water and lime water in small amounts are also useful for
assisting mechanically in the digestion of milk. Milk at ordinary prices
is one of the cheapest foods that can be used.
[Illustration: FIG. 23.--DIRT IN A SAMPLE OF UNSANITARY MILK.]
102. Sanitary Condition of Milk.--Equally as important as composition
is the sanitary condition or wholesomeness of milk. Milk is a food
material which readily undergoes fermentation and is a medium for the
distribution of germ diseases. The conditions under which it is produced
and the way in which it is handled determine largely its sanitary
value, and are of so much importance in relation to public health that
during recent years city and state boards of health have introduced
sanitary inspection and examination of milk along with the chemical
tests for detecting its adulteration. Some of the more frequent causes
of contaminated and unsound milk are: unhealthy animals, poor food and
water, unsanitary surroundings of the animals, and lack of cleanliness
and care in the handling and transporting of the milk. Outbreaks of
typhoid and scarlet fevers and other germ diseases have frequently been
traced to a contaminated milk supply.[37]
103. Certified Milk.--When milk is produced under the most sanitary
conditions, the number of bacterial bodies per cubic centimeter is
materially reduced. In order to supply high grade milk containing but
few bacteria, special precautions are taken in the care of the animals,
and in the feeding and milking, and all sources of contamination of the
milk are eliminated as far as possible. Such milk, when sold in
sterilized bottles, is commonly called "certified milk," indicating that
its purity is guaranteed by the producer and that the number of bacteria
per unit does not exceed a certain standard, as 8000 per cubic
centimeter. Ordinary market milk contains upwards of 50,000.
104. Pasteurized Milk.--In order to destroy the activity of the
bacterial organisms, milk is subjected to a temperature of 157° F. for
ten minutes or longer, which process is known as pasteurization. When
milk is heated to a temperature above 180°, it is sterilized. Below
157°, the albumin is not coagulated. By pasteurizing, milk is much
improved from a sanitary point of view, and whenever the milk supply is
of unknown purity, it should be pasteurized.[38] After the milk has been
thus treated, the same care should be exercised in keeping it protected
to prevent fresh inoculation or contamination, as though it were
unpasteurized milk. For family use milk can be pasteurized in small
amounts in the following way: Before receiving the milk, the receptacle
should be thoroughly cleaned and sterilized with boiling water or dry
heat, as in an oven. The milk is loosely covered and placed in a pan of
water, a false bottom being in the pan so as to prevent unequal heating.
The water surrounding the milk is gradually heated until a temperature
of 159° F. is registered, and the milk is kept at this temperature for
about ten minutes. It is then cooled and placed in the refrigerator.
[Illustration: FIG. 24.--PASTEURIZING MILK.]
105. Tyrotoxicon.--Tyrotoxicon is a chemical compound produced by a
ferment body which finds its way into milk when kept in unsanitary
surroundings. It induces digestion disorders similar to cholera, and
when present in large amounts, may prove fatal. It sometimes develops in
cream, ice cream, or cheese, but only when they have been kept in
unclean places or produced from infected milk.
601. Color of Milk is often taken as a guide to its purity and
richness in fat. While a yellow tinge is usually characteristic of
milks rich in fat, it is not a hard and fast rule, for frequently
light-colored milks are richer in fat than yellow-tinged ones. The
coloring material is independent of the percentage of fat, and it is not
always safe to judge the richness of milk on the basis of color.
107. Souring of Milk.--Souring of milk is due to the action of the
lactic acid organism, which finds its way into the milk through
particles of dust carried in the air or from unclean receptacles which
contain the spores of the organism.[39] When milk sours, a small amount
of sugar is changed to lactic acid which reacts upon the casein,
converting it from a soluble to an insoluble condition. When milk is
exposed to the air at a temperature of from 70° to 90° F., lactic acid
fermentation readily takes place. At a low temperature the process is
checked, and at a high temperature the organisms and spores are
destroyed. In addition to lactic acid ferments, there are large numbers
of others which develop in milk, changing the different compounds of
which milk is composed. In the processes of butter and cheese making,
these fermentation changes are controlled so as to develop the flavor
and secure the best grades of butter and cheese.
108. Use of Preservatives in Milk.--In order to check fermentation,
boric acid, formalin, and other preservatives have been proposed.
Physiologists object to their use because the quantity required to
prevent fermentation is often sufficient to have a medicinal effect.
The tendency is to use excessive amounts, which may interfere with
normal digestion of the food. Milk that is cared for under the most
sanitary conditions has a higher dietetic value and is much to be
preferred to that which has been kept sweet by the use of preservatives.
109. Condensed Milk is prepared by evaporating milk in vacuum pans
until it is reduced about one fourth in bulk, when it is sealed in cans,
and it will then keep sweet for a long time. Occasionally some cane
sugar is added to the evaporated product. When diluted, evaporated milk
has much the same composition as whole milk. When a can of condensed
milk has been opened, the same care should be exercised to prevent
fermentation as if it were fresh milk.
110. Skim Milk differs in composition from whole milk in fat content.
When the fat is removed by the separator, there is often left less than
one tenth of a per cent. Skim milk has a much higher nutritive value
than is generally conceded, and wherever it can be procured at a
reasonable price it should be used in the dietary as a source of
protein.
111. Cream ranges in fat content from 15 to 35 per cent. It is
generally preferred to whole milk, although it is not as well balanced a
food, because it is deficient in protein. Cream should contain at least
25 per cent of fat.
112. Buttermilk is the product left after removal of the fat from
cream by churning. It has about the same amount of nutrients as skim
milk. The casein is in a slightly modified form due to the development
of lactic acid during the ripening of the cream, and on this account
buttermilk is more easily digested and assimilated by many individuals
than milk in other forms. The development of the acid generally reduces
the number of species of other than the lactic organisms, and these are
increased.
113. Goat's Milk is somewhat richer in solids than cow's milk,
containing about one per cent more proteids, a little more fat, and less
sugar. When used as a substitute for human or cow's milk, it generally
needs to be slightly diluted, depending, however, upon the composition
of the individual sample.
114. Koumiss is a fermented beverage made from milk by the use of
yeast to secure alcoholic fermentation. Koumiss contains about one per
cent each of lactic acid and alcohol, and the casein and other nutrients
are somewhat modified by the fermentation changes. Koumiss is generally
considered a non-alcoholic beverage possessing both food and dietetic
value.
115. Prepared Milks.--Various preparations are made to resemble milk
in general composition. These are mechanical mixtures of sugar, fats,
and proteids. Milk sugar, casein, or malted proteids are generally the
materials employed in their preparation. Often the dried and pulverized
solids of skim milk are used. Many of the prepared milks are deficient
in fat. While they are not equal to cow's milk, their use is often made
necessary from force of circumstances.
116. Human Milk is not as rich in solid matter as cow's milk. It
contains about the same amount of fat, one per cent more sugar, and one
per cent less proteids. In human milk nearly one half of the protein is
in the form of albumins, while in cow's milk there is about one fifth in
this form. The fat globules are much smaller than those of cow's milk.
In infant feeding it is often necessary to modify cow's milk by the
addition of water, cream, and milk sugar, so as to make it more nearly
resemble in composition human milk.
[Illustration: FIG. 25.--APPARATUS USED IN TESTING MILK.
1, pipette; 2, lactometer; 3, acid measure; 4, centrifuge; 5, test
bottle.]
117. Adulteration of Milk.--Milk is not as extensively adulterated as
it was before the passage and enforcement of the numerous state and
municipal laws regulating its inspection and sale. The most frequent
forms of adulteration are addition of water and removal of cream. These
are readily detected from the specific gravity and fat content of the
milk. The specific gravity of milk is determined by means of the
lactometer, an instrument which sinks to a definite point in pure milk.
In watered milk it sinks to greater depth, depending upon the amount of
water added. The fat content of milk is readily and accurately
determined by the Babcock test, in which the fat is separated by
centrifugal action. For the detection of adulterated milk the student
is referred to Chapter VI, "Chemistry of Dairying," by Snyder.
BUTTER
118. Composition.--Butter is made by the churning or agitation of
cream and is composed mainly of milk fats and water, together with
smaller amounts of ash, salt, casein, milk sugar, and lactic acid.
Average butter has the following composition:
============================
|Per Cent
Water | 10.5
Ash and salt | 2.5
Casein and albumin | 1.0
Fat | 86.0
============================
When butter contains an abnormal amount of water, it is considered
adulterated. According to act of Congress standard butter should not
contain over 16 per cent of water nor less than 82.5 per cent of fat.
119. Digestibility of Butter.--Digestion experiments show that
practically all of the fat, 98 per cent, is digestible and available for
use by the body. Butter is valuable only for the production of heat and
energy. Alone, it is incapable of sustaining life, because it contains
no proteid material. It is usually one of the more expensive items of
food, but it is generally considered quite necessary in a ration.[5] It
has been suggested that it takes an important part mechanically in the
digestion of food.
120. Adulteration of Butter.--In addition to containing an excess of
water, butter is adulterated in other ways. Old, stale butter is
occasionally melted, washed, salted, and reworked. This product is known
as renovated butter, and has poor keeping qualities. Frequently
preservatives are added to such butter to delay fermentation changes.
Oleomargarine and butterine are made by mixing vegetable and animal
fats.[40] Highly colored stearin, cotton-seed oil, and lard are the
usual materials from which oleomargarine is made. It has practically the
same composition, digestibility, and food value as butter. When sold
under its true name and not as butter, there is no objection, as it is a
valuable food and supplies heat and energy at less cost than butter. The
main objection to oleomargarine and butterine is that they are sold as
butter.[41]
The coloring of butter is not generally looked upon as adulteration, for
butter naturally has a more or less yellow tinge. According to an act of
Congress, butter colors of a non-injurious character are allowed to be
used.
CHEESE
121. General Composition.--Cheese, is made by the addition of rennet
to ripened milk, resulting in coagulation of the casein, which
mechanically combines with the fat. It differs from butter in
composition by containing, in addition to fat, casein and appreciable
amounts of mineral matter. The composition varies with the character of
the milk from which the cheese was made. Average milk produces cheese
containing a larger amount of fat than proteids, while cheese from
skimmed or partially skimmed milk is proportionally poorer in fat.
Ordinarily there is about 35 per cent of water, 33 per cent of fat, and
27 per cent of casein, and albumin or milk proteids, the remainder being
ash, salt, milk sugar, and lactic acid. Cheese is characterized by its
large percentage of both fat and protein, and has high food value. It
contains more fat and protein than any of the meats; in fact, there are
but few foods which have such liberal amounts of these nutrients as
cheese.
The odor and flavor of cheese are due to workings of bacteria which
result in the production of aromatic compounds. The purity and condition
of the milk, as well as the method of manufacture and the kind of
ferment material used, determine largely the flavor and odor. Cheese is
generally allowed to undergo a ripening or curing process before it is
used as food. The changes resulting consist mainly in increased
solubility of the proteids, with the formation of a small amount of amid
and aromatic compounds.[42]
122. Digestibility.--Cheese is popularly considered an indigestible
food, but extended experiments show that it is quite completely
digested, although in the case of some individuals not easily digested.
In general, about 95 per cent of the fat and 92 per cent and more of the
protein is digested, depending upon the general composition of the
cheese and the digestive capacity of the individual. As far as total
digestibility is concerned, there appears to be but little difference
between green and well-cured cheese. So far as ease of digestion is
concerned, it is probable that some difference exists. There is also but
little difference in digestibility resulting from the way in which milk
is made into cheese, the nutrients of Roquefort, Swiss, Camembert, and
Cheddar being about equally digestible.[13] The differences in odor and
taste are due to variations in kind and amount of bacterial action. When
combined with other foods, cheese may exercise a beneficial influence
upon digestion in the same way as noted from the use of several foods in
a ration. No material differences were observed in digestibility when
cheese was used in small amounts, as for condimental purposes, or when
used in large amounts to furnish nutrients. Artificial digestion
experiments show that cheese is more readily acted upon by the
pancreatic than by the gastric fluids, suggesting that cheese undergoes
intestinal rather than gastric digestion. It is possible this is the
reason that cheese is slow of digestion in the case of some individuals.
123. Use in the Dietary.--Cheese should be used in the dietary
regularly and in reasonable amounts, rather than irregularly and then in
large amounts. Cheese is not a luxury, but ordinarily it is one of the
cheapest and most nutritious of human foods. A pound of cheese costing
15 cents contains about a quarter of a pound of protein and a third of a
pound of fat; at the same price, beef yields only about half as much fat
and less protein. Cheese at 18 cents per pound furnishes more available
nutrients and energy than beef at 12 cents per pound. In the dietary of
European armies, cheese to a great extent takes the place of beef. See
Chapter XVI.
124. Cottage Cheese is made by coagulating milk and preparing the curd
by mixing with it cream or melted butter and salt or sugar as desired.
When milk can be procured at little cost, cottage cheese is one of the
cheapest and most valuable foods.[43]
125. Different Kinds of Cheese.--By the use of different kinds of
ferments and variations in the process of manufacture different types or
kinds of cheese are made, as Roquefort, Swiss, Edam, Stilton, Camembert,
etc. In the manufacture of Roquefort cheese, which is made from goats'
and ewes' milk, bread is added and the cheese is cured in caves,
resulting in the formation of a green mold which penetrates the cheese
mass, and produces characteristic odor and flavor. Stilton is an English
soft, rich cheese of mild flavor, made from milk to which cream is
usually added. It is allowed to undergo an extended process of ripening,
often resulting in the formation of bluish green threads of fungus.
Limburger owes its characteristic odor and flavor to the action of
special ferment bodies which carry on the ripening process. Neufchatel
is a soft cheese made from sweet milk to which the rennet is added at a
high temperature. After pressing, it is kneaded and worked, and then put
into packages and covered with tin foil.
126. Adulteration of Cheese.--The most common forms of adulteration
are the manufacture of skim-milk cheese by the removal of the fat from
the milk, and substitution of cheaper and foreign fats, making a product
known as filled cheese. When not labeled whole milk cheese, or sold as
such, there is no objection to skim-milk cheese. It has a high food
value and is often a cheap source of protein. The manufacture of filled
cheese is now regulated by the national government, and all such cheese
must pay a special tax and be properly labeled. As a result, the amount
of filled cheese upon the market has very greatly decreased, and cheese
is now less adulterated than in former years. The national dairy law
allows the use of coloring matter of a harmless nature in the
manufacture of cheese.
127. Dairy Products in the Dietary.--The nutrients in milk are
produced at less expense for grain and forage than the nutrients in
beef, hence from a pecuniary point of view, dairy products, as milk and
cheese, have the advantage. In the case of butter, however, the cost
usually exceeds that of meat. In older agricultural regions, where the
cost of beef production reaches the maximum, dairying is generally
resorted to, as it yields larger financial returns, and as a result more
cheese and less beef are used in the dietary. As the cost of meats is
enhanced, dairy products, as cheese, naturally take their place.
CHAPTER VIII
MEATS AND ANIMAL FOOD PRODUCTS
128. General Composition.--Animal tissue is composed of the same
classes of compounds as plant tissue. In each, water makes up a large
portion of the weight, and the dry matter is composed of nitrogenous and
non-nitrogenous compounds, and ash or mineral matter. Plants and animals
differ in composition not so much as to the kinds of compounds, although
there are differences, but more in the percentage amounts of these
compounds. In plants, with the exception of the legumes, the protein
rarely exceeds 14 per cent, and in many vegetable foods, when prepared
for the table, there is less than 2 per cent. In meats the protein
ranges from 15 to 20 per cent. The non-nitrogenous compounds of plants
are present mainly in the form of starch, sugar, and cellulose, while in
animal bodies there are only traces of carbohydrates, but large amounts
of fat. Fat is the chief non-nitrogenous compound of meats; it ranges
between quite wide limits, depending upon kind, age, and general
condition of the animal. Meats contain the same general classes of
proteins as the vegetable foods; in each the proteins are made up of
albumins, glubulins, albuminates, peptone-like bodies, and insoluble
proteids. The larger portion of the protein of meats and cereals is in
insoluble forms. The meat juices, which contain the soluble portion of
the proteins, constitute less than 5 percent of the nitrogenous
compounds. Meats contain less amid substances than plants, in which the
amids are produced from ammonium compounds and are supposed to be
intermediate products in the formation of proteids, while in the animal
body they are derived from the proteids supplied in the food and, it is
generally believed, cannot form proteids. Albuminoids make up the
connective tissue, hair, and skin, and are more abundant in animal than
in plant tissue. One of the chief albuminoids is gelatine. Both plant
and animal foods undergo bacterial changes resulting in the production
of alkaloidal bodies known as ptomaines, of which there are a large
number. These are poisonous and are what cause putrid and stale meat to
be unwholesome. The protein in meat differs little in general
composition from that of vegetable origin; differences in structure and
cleavage products between the two are, however, noticeable.
[Illustration: FIG. 26.--MEAT AND EXTRACTIVE SUBSTANCES.]
While meats from different kinds of animals have somewhat the same
general composition, they differ in physical properties, and also in the
nature of the various nutrients. For example, pork contains less protein
than beef, but the protein of pork is materially different from that of
beef, as a larger portion is in the form of soluble proteids, while in
beef more is present in an insoluble form. Not only are differences in
the percentage of individual proteins noticeable, but there are equally
as great differences in the fats. As for example: some of the meats have
a larger proportion of the fat as stearin than do others. Hence meats
differ in texture and taste more than in nutritive value, due to the
variations in the percentage of the different proteins, fats, and
extractive material, rather than to differences in the total amounts of
these compounds. The taste and flavor of meat is to a large extent
influenced by the amount of extractive material.
While the nutrients of meats are divided into classes, as proteins and
fats, there are a large number of separate compounds which make up each
of the individual classes, and there are also small amounts of
compounds which are not included in these groups.
[Illustration: FIG. 27.--STANDARD CUTS OF BEEF.
(From Office of Experiment Station Bulletin.)]
129. Beef.--About one half of the weight of beef is water; the lean
meat contains a much larger amount than the fat. As a rule, the parts of
the animal that contain the most fat contain the least water. In some
meats there is considerable refuse, 25 to 30 per cent. In average meat
about 12 per cent of the butcher's weight is refuse and non-edible
parts.[44] A pound of average butcher's meat is about one half water,
and over 10 per cent waste and refuse, which leaves less than 40 per
cent fat and protein. Meat is generally considered to have a high
nutritive value, due to the comparatively large amounts of fat and
protein. Beef contains more protein than any vegetable food, except the
legumes, and from 1 to 1.5 per cent mineral matter, exclusive of bone.
Some of the mineral matter is chemically united with the protein and
other compounds. While figures are given for average composition of
beef, it is to be noted that wide variations are frequently to be met
with, some samples containing a much larger amount of waste and
trimmings than others, and this influences the percent of the nutritive
substances. In making calculations of nutrients consumed, as in dietary
studies, the figures for average composition of meat should be used only
in cases where the samples do not contain an excess either of fat or
trimmings.[45] When very lean, there is often a large amount of refuse,
and the meat contains less dry matter and is of poorer flavor than from
animals in prime condition. In the case of very fat animals, a large
amount of waste results, and the flavor is sometimes impaired.
130. Veal differs from beef in containing a smaller amount of dry
matter, richer in protein, but poorer in fat. Animals differ in
composition at different stages of growth in much the same way as
plants. In the earlier stages protein predominates in the plant tissue,
while later the carbohydrates are added in larger amounts, reducing the
percentage content of protein. In animals the same is noticeable. Young
animals are, pound for pound, richer in protein than old animals. While
in the case of vegetables the increase in size, or rotundity, is due to
starch and carbohydrates, in animals it is due to the addition of fat.
But plants, like animals, observe the same general laws as to changes in
composition at different stages of growth.
[Illustration: FIG. 28.--STANDARD CUTS OF MUTTON.
(From Office of Experiment Station Bulletin.)]
131. Mutton.--There is about the same amount of refuse matter in mutton
as in beef. In a side of mutton about 19 percent: are trimmings and
waste, and in a side of beef 18.5 per cent. Mutton, as a rule, contains
a little more fat and dry matter than beef, and somewhat less protein. A
side of beef, as purchased, contains about 50 per cent of water, 14.5
per cent protein, and 16.8 per cent of fat, while a side of mutton, as
purchased, contains 42.9 per cent water, 12.5 per cent protein, and 24.7
per cent fat. A pound of beef yields a smaller number of calories by 25
per cent than a pound of mutton. At the same price per pound more
nutrients can be purchased as mutton than as beef. The differences in
composition between lamb and mutton are similar to those between veal
and beef; viz. a larger amount of water and protein and a smaller amount
of fat in the same weight of the young animals. Differences in
composition between the various cuts of lamb are noticeable. The leg
contains the least fat and the most protein, while the chuck is richest
in fat and poorest in protein. As in the case of beef, many of the
cheaper cuts contain as much or more nutrients than the more expensive
cuts. They are not, however, as palatable and differ as to toughness and
other physical characteristics.
[Illustration: FIG. 29.--STANDARD CUTS OF PORK.
(From Office of Experiment Station Bulletin.)]
132. Pork is characterized by a high per cent of fat and a
comparatively low per cent of protein. It is generally richest in fat of
any of the meats. The per cent of water varies with the fatness of the
animal; in very fat animals there is a smaller amount, while lean
animals contain more. In lean salt pork there is about 20 per cent
water, and in fat salt pork about 7 per cent. There is less refuse and
waste in pork than in either beef or mutton. Ham contains from 14 to 15
per cent of refuse, and bacon about 7 per cent. Bacon has nearly twice
as much fat and a smaller amount of protein than ham. A pound of bacon,
as purchased, will yield nearly twice as much energy or fuel value as a
pound of ham. Digestion experiments show that bacon is quite readily and
completely digested and is often a cheaper source of fat and protein
than other meats. There is about three times as much fat in bacon as in
beef. When prepared for the table bacon contains, from 40 to 50 per cent
of fat. A pound of high grade, lean bacon furnishes from 0.1 to 0.3 of a
pound of digestible protein and from 0.4 to 0.6 of a pound of digestible
fat, which is about two thirds as much fat as is found in butter. Bacon
contains nearly as much digestible protein as other meats and from two
to three times as much fat, making it, at the same price per pound, a
cheaper food than other meats. In salt pork there is from 60 to 85 per
cent of fat, and less protein than in bacon. The protein and fat of pork
differ from those in beef not only in percentage amounts, but also in
the nature of the individual proteins and fats. The composition of pork
varies with the nature of the food that is consumed by the animal.
Experiments show that it is possible by judicious feeding in the early
stages of growth to produce pork with the maximum of lean meat and the
minimum of fat. After the animal has passed a certain period, it is not
possible by feeding to materially influence the percentage of nutrients
in the meat. The flavor, too, of pork, as of other meats, is dependent
largely upon the nature of the food the animal consumes. When there is a
scant amount of available protein in the ration, the meat is dry, nearly
tasteless, and contains less of the soluble nitrogenous compounds which
impart flavor and individuality.
133. Lard is prepared from the fat of swine, and is separated from
associated tissue by the action of heat. A large amount of fat is found
lining the back of the abdominal cavity, and this is known as leaf lard.
Slight differences are noticeable in the composition and quality of lard
made from different parts of the hog. Leaf lard is usually considered
the best. Lard is composed of the three fats, olein, stearin, and
palmatin, and has a number of characteristic physical properties, as
specific gravity, melting point, iodine absorption number, as well as
behavior with various reagents, and these enable the mixing of other
fats with lard to be readily detected. Lard is used in the preparation
of oleomargarine, and it is also combined with various vegetable oils,
as cotton-seed oil, in the making of imitation or compound lards.[46]
Lard substitutes differ little in general composition from pure lard,
except in the structure of the crystals and the percentage of the
various individual fats.
134. Texture and Toughness of Meats.--In discussing the texture of
meats, Professor Woods states:[45]
"Whether meats are tough or tender depends upon two things: the
character of the walls of the muscle tubes and the character of the
connective tissues which bind the tubes and muscles together. In
young and well-nourished animals the tube walls are thin and
delicate, and the connective tissue is small in amount. As the
animals grow older or are made to work (and this is particularly
true in the case of poorly nourished animals), the walls of the
muscle tubes and the connective tissues become thick and hard. This
is the reason why the flesh of young, well-fed animals is tender
and easily masticated, while the flesh of old, hard-worked, or
poorly fed animals is often so tough that prolonged boiling or
roasting seems to have but little effect on it.
"After slaughtering, meats undergo marked changes in texture. These
changes can be grouped under three classes or stages. In the first
stage, when the meat is just slaughtered, the flesh is soft, juicy,
and quite tender. In the next stage the flesh stiffens and the meat
becomes hard and tough. This condition is known as _rigor mortis,_
and continues until the third stage, when the first changes of
decomposition set in. In hot climates the meat is commonly eaten in
either the first or second stage. In cold climates it is seldom
eaten before the second stage, and generally, in order to lessen
the toughness, it is allowed to enter the third stage, when it
becomes soft and tender, and acquires added flavor. The softening
is due in part to the formation of lactic acid, which acts upon the
connective tissue. The same effect may be produced, though more
rapidly, by macerating the meat with weak vinegar. Meat is
sometimes made tender by cutting the flesh into thin slices and
pounding it across the cut ends until the fibers are broken."
135. Influence of Cooking upon the Composition of Meats.[47]--It is
believed by many that losses are prevented and the nutritive value
conserved when, in the cooking of meat, it is placed directly into
boiling water rather than into cold water and then brought to the
boiling point and cooked. Extensive experiments have been made by Dr.
Grindley in regard to this and other points connected with the cooking
of meats, and in general it was found that the temperature of the water
in which the meat was placed made little difference in its nutritive
value or the amount of material extracted. It was found that by both
methods there was dissolved 2.3 percent of the protein matter, 1 percent
of the nitrogenous extractives, 1.6 per cent of non-nitrogenous
material, and 0.8 per cent of ash, of the raw meat, which was equivalent
to about 13 per cent of the total proteid material and 81 percent of the
ash. The cold water extract contained bodies coagulated by heat. Cold
water did not extract any of the fat, but during the process of cooking,
appreciable amounts were lost mechanically. Cooked meats were found to
be less soluble in cold water than raw meats. During the process of
boiling, meat shrinks in weight about 40 or 45 per cent, depending
mainly upon the size of the pieces and the content of fat. The loss in
weight is practically a loss of water, and the loss of nutrients, all
told, amounts to about 4 per cent, or more, depending upon the
mechanical loss.[48] But slight differences were found in the
composition of the meats cooked three and five hour periods.
"Careful study in this laboratory has shown that when meat is
cooked in water at 80° to 85° C., placing meat in hot or cold water
at the start has little effect on the amount of nutrients in the
meat which passes into the broth. The meat was in the form of
cubes, one to two inches, and in pieces weighing from one to two
pounds.
"It is commonly supposed that when meat is plunged into boiling
water, the albumin coagulates and forms a crust, which prevents the
escape of nutritive materials into the broth. It is also believed
that if a rich broth is desired, to be used either as a soup or
with the meat as a stew, it is more desirable to place the meat in
cold water at the start. From the results of these experiments,
however, it is evident that, under these conditions, there can be
little advantage in using hot or cold water at the beginning. When
meats were cooked by dry heat, as in roasting, a larger amount of
nutrients was rendered soluble in water than during boiling. The
losses of nutrients were much smaller when meats were cooked by dry
heat than when cooked in water, being on the average, water 35 per
cent, nitrogenous extractives 9 per cent, non-nitrogenous
extractives 17 per cent, fat 7 per cent, ash 12 per cent, and a
small loss of protein."
The nutrients in the broth of the meat started in hot water amounted to
about 1 per cent of protein, 1 per cent of fat, and O.5 per cent of
ash, the amount of nutrients being directly proportional to the length
of time and temperature of the cooking. In general, the larger the
pieces, the smaller the losses. Beef that has been used in the
preparation of beef tea loses its extractive materials, which impart
taste and flavor, but there is only a small loss of actual nutritive
value. Clear meat broth contains little nutriment--less than unfiltered
broth. Most of the nitrogenous material of the broth is in the form of
creatin, sarkin, and xanthin, nitrogenous extractives or amid substances
having a much lower food value than proteids. Experiments show that some
of these extractives have physiological properties slightly stimulating
in their action, and it is believed the stimulating effect of a meat
diet is in part due to these.[49] They are valuable principally for
imparting taste and flavor, and cannot be regarded as nutrients. The
variations in taste and flavor of meats from different sources are due
largely to differences in extractive material.
"In general, the various methods of cooking materially modify the
appearance, texture, and flavor of meat, and hence its
palatability, but have little effect on total nutritive value.
Whether it be cooked in hot water, as in boiling or stewing, or by
dry heat, as in roasting, broiling, or frying, meat of all kinds
has a high food value, when judged by the kind and amount of
nutrient ingredients which are present." [50]
Beef extracts of commerce contain about 50 per cent of extractive
matters, as amids, together with smaller amounts of soluble proteids;
ash, mainly added salt, is also present in liberal amounts (20 per
cent). Beef extracts have condimental value imparting taste and flavor,
which make them useful for soup stocks, but they furnish little in the
way of nutritive substance.
136. Miscellaneous Meat Products.--By combining different parts of the
same animal, or different meats, a large number of products known as
sausage are made. These vary in composition with the ingredients used.
In general, they are richer in fat than beef and contain about the same
amount of protein. Potato flour and flour from cereals are sometimes
used in their preparations, but the presence of any material amount,
unless so stated on the package, is considered an adulterant.
Pickled meats are prepared by the use of condiments, as salt, sugar,
vinegar, and saltpeter. During the smoking and curing of meats, no
appreciable losses of nutrients occur.[51] The smoke acts as a
preservative, and imparts condimental properties. Saltpeter (potassium
nitrate) has been used from earliest times in the preparation of meats;
it preserves color and delays fermentation changes. When used in
moderate amounts it cannot be regarded as a preservative or injurious to
health. Excessive amounts, however, are objectionable. Smoked meats,
prepared with or without saltpeter, give appreciable reactions for
nitrites, compounds formed during combustion of the wood by which the
meat was smoked. Many vegetables contain naturally much larger amounts
of nitrates, taken from the soil as food, than meat that has been
preserved with saltpeter.[52]
137. Poultry.--The refuse and waste from chickens, as purchased on the
market, ranges from 15 to 30 per cent. The fat content is much lower
than in turkeys or ducks, the largest amount being found in geese. The
edible portion of all fowls is rich in protein, particularly the dark
meat, and the food value is about equal to that of meat in general. When
it is desired to secure a large amount of protein with but little fat,
chicken supplies this, perhaps, better than any other animal food. A
difference is observed in the composition of the meat of young and old
fowls similar to that between beef and veal. The physical composition
and, to a slight extent, the solubility of the proteids are altered by
prolonged cold storage, the difference being noticeable mainly in the
appearance of the connective tissue of the muscles. In discussing
poultry as food, Langworthy states:[53]
"A good, fresh bird shows a well-rounded form, with neat, compact
legs, and no sharp, bony angles on the breast, indicating a lack of
tender white meat. The skin should be a clear color (yellow being
preferred in the American market) and free from blotches and pin
feathers; if it looks tight and drawn, the bird has probably been
scalded before being plucked. The flesh should be neither flabby
nor stiff, but should give evenly and gently when pressed by the
finger."
138. Fish.--From 30 to 60 per cent of the weight of fresh fish is
refuse. The edible portion contains from 35 to 50 per cent, and in some
cases more, of water. The dry matter is rich in protein; richer than
many meats. The nutrients in fish range between comparatively wide
limits, the protein in some cases being as low as 6 per cent, in
flounder, and in others as high as 30 per cent, in dried codfish. The
amount of fat, except in a few cases, as salmon and trout, is small.
Salmon is the richest in fat of any of the fishes. When salted and
preserved, the proportion of water is lessened and that of the nutrients
is increased. Fish can take the place of meat in the dietary, but it is
necessary to add a larger amount of fat to the ration because of the
deficiency of most fish in this ingredient. Fish has about the same
digestibility as meats. It is believed by many to be valuable because it
supplies a large amount of available phosphates. Analyses, however, show
that the flesh of fish contains no more phosphorus compounds than meats
in general, and its food value is due to protein rather than to
phosphates.[54]
Fish appears to be as completely and easily digested as meats.
Differences in flavor, taste, and palatability are due to small amounts
of flavors and extractive materials, varying according to the food
consumed by the fish and the conditions under which they lived. The
flesh of fish decays more readily than that of other meats and produces
ptomaines, or toxic substances, which are the result of fermentation
changes usually associated with putrefaction. Cases of poisoning from
eating unsound fish are not infrequent.[55]
Shellfish have about the same general composition as fish. In clams
there is a larger amount of dry matter than in oysters, which contain
about 12 per cent, half of which is protein. When placed in fresh water,
the oyster increases in size and undergoes the process known as
"fattening." Oftentimes impure water is used for this purpose, which
makes the eating of raw oysters a questionable practice from a sanitary
point of view, as the water in which they are floated often contains
disease-producing germs, as typhoid. During the process of fattening,
although the oyster increases in size and weight, it decreases in
percentage of nutrients. In discussing the composition of oysters,
Atwater states:[7]
"They come nearer to milk than almost any other food material as
regards both the amounts and relative proportions of nutrients."
139. Eggs, General Composition.--Eggs are a type of concentrated
nitrogenous food. About 75 per cent (shell removed) is water, about one
third is yolk, and a little over 50 per cent is albumin or white. The
shell makes up from 10 to 12 per cent of the weight. The yolk and white
differ widely in composition. The yolk contains a much larger per cent
of solids than the white, and is rich in both fat and protein, from a
third to a half of the weight being fat. The white has about the same
amount of water, 88 per cent, as average milk, but, unlike milk, the dry
matter is mainly albumin. The entire egg (edible portion) contains
about equal parts of fat and protein; 12 to 13 per cent of each and an
appreciably large amount of ash or mineral matter,--from 0.8 to 1 per
cent, consisting mainly of phosphates associated with the albumin. There
is no material difference in chemical composition between white and dark
shelled eggs, or between eggs with different colored yolks. It is simply
a question of coloring matter. The egg is influenced to an appreciable
extent by feed and general care of the fowls. The egg and the potato
contain about the same amount of water. They are, however, distinct
types of food, the potato being largely composed of carbohydrates and
the egg of protein and fat. Eggs resemble meat somewhat in general
composition, although they contain rather less of protein and fat. When
eggs are boiled there is a loss of weight due to elimination of water;
otherwise the composition is unaltered, the coagulation of the albumin,
as stated in Chapter I, consisting simply in a rearrangement of the
atoms of the molecule. The egg is particularly valuable in the dietary
of the convalescent, when it is desired to secure the maximum amount of
phosphorus in organic combination.
[Illustration: FIG. 30.--GRAPHIC COMPOSITION OF AN EGG.]
The flavor of eggs is in part due to the food supplied to the fowls, as
well as the age of the egg. Experiments show that onions and some other
vegetables, when fed to fowls, impart odors and taste to the eggs. The
keeping qualities of eggs are also dependent upon the food supplied. In
experiments at the Cornell Experiment Station, when hens were fed on a
narrow, nitrogenous ration, a large number of eggs were produced
containing the minimum amount of solid matter and of poor keeping
quality, while a larger sized egg of better keeping quality was obtained
when a variety of foods, nitrogenous and non-nitrogenous, was supplied.
140. Digestibility of Eggs.--Digestion experiments show that there is
but little difference in the digestibility of eggs cooked in different
ways. A noticeable difference, however, is observed in the rapidity with
which the albumin and proteids are dissolved in a pepsin solution. In
general, it was found that, when the albumin was coagulated at a
temperature of 180°, it was more rapidly and completely dissolved in the
pepsin than when coagulated at a temperature of 212°. When eggs were
cooked at a temperature of 212°, the hard-boiled eggs appeared to be
slightly more digestible than the soft-boiled eggs, but the digestion
was not as complete as when the cooking was done at a temperature of
180°; then no difference in digestibility was found between eggs cooked
for a short or a long time. The egg is one of the most completely
digested of all foods, practically all the protein and fat being
absorbed and available to the body. Langworthy, in discussing
Jorissenne's investigations on the digestibility of eggs, states:[53]
"The yolk of raw, soft-boiled, and hard-boiled eggs is equally
digestible. The white of soft-boiled eggs, being semi-liquid,
offers little more resistance to the digestive juices than raw
white. The white of a hard-boiled egg is not generally very
thoroughly masticated. Unless finely divided, it offers more
resistance to the digestive juices than the fluid or semi-fluid
white, and undigested particles may remain in the digestive tract
many days and decompose. From this deduction it is obvious that
thorough mastication is a matter of importance. Provided
mastication is thorough, marked differences in the completeness of
digestion of the three sorts of eggs, in the opinion of the writer
cited, will not be found."
141. Use of Eggs in the Dietary.--When eggs are at the same price per
dozen as meat is per pound, they furnish a larger amount of nutrients.
In general, a dozen eggs have a little higher food value than a pound of
meat. Eggs are usually a cheaper source of food because a smaller amount
is served than of meat. When eggs are 25 cents per dozen, the cost of
ten eggs for a family of five is less than that of a pound or a pound
and a quarter of beef at 22 cents per pound. The meat, however, would
furnish the larger amount of nutrients. Eggs are valuable, too, in the
dietary because they are frequently combined with flour, cereal
products, and vegetables, which contain a large amount of starch, and
some of which contain small amounts of protein. This combination
furnishes a balanced ration, as well as secures palatability and good
mechanical combination of the foods. Eggs in combination with flour,
sugar, butter, and other materials have equally as great a value as when
used alone and as a substitute for meat.
Eggs vary in weight from 17.5 to 28 ounces, and more per dozen. They
should be purchased and sold by weight. When stored, eggs lose weight.
The egg cannot be considered as entirely germ proof, and care is
necessary in its handling and use, the same as with other food articles.
The cause of the spoiling of eggs is due largely to exterior bacterial
infection.
CANNED MEATS
142. General Composition.--Canned meats differ but little in
composition from fresh meats. Usually during the process of cooking and
canning there is a slight increase in the amount of dry matter, but the
relative proportion of protein and fat is about the same as in fresh
meat. It is frequently stated that the less salable parts are used in
the preparation of canned meats, as it is possible by cooking and the
addition of condiments to conceal the inferior physical properties. As
to the accuracy of these statements, the author is unable to say. The
shrinkage or loss in weight during canning amounts to from 30 to 40 per
cent. The liquids in which the cooking and parboiling are done are
sometimes used in the preparation of beef extracts. Salt, saltpeter, and
condiments are generally added during the canning process. Saltpeter is
used, as it assists in retaining the natural color and prevents some
objectionable fermentation changes. In moderate amounts it is not
generally considered an adulterant. An extensive examination by Wiley
and Bigelow of packing-house products and preserved meats showed that of
the latter only a small amount contained objectionable preservatives.
The authors, after an extended investigation, reported favorably upon
their composition and sanitary value, saying they found "so little to
criticise and so much to commend in these necessary products." In this
bulletin they do not classify saltpeter as an adulterant.[51]
Where fresh meats cannot be secured, canned meats are often
indispensable. Usually the nutrients of canned meats cost more than
those of fresh meats, and in their use as food much care should be
exercised to prevent contamination after opening the cans. Occasionally
the meat contains ferment materials that have not been entirely
destroyed during cooking, and these, when the cans are stored in warm
places, develop and cause deleterious changes to occur. Consequently
canned meats should be stored at a low temperature. By recent
congressional act, these preparations are now made under the
supervision of government inspectors. All diseased animals are
rejected, and the sanitary conditions under which the meat is prepared
have been greatly improved. Formerly, the most frequent forms of
adulteration were substitution of one meat for another, as the mixing of
veal with chicken, and the use of preservatives, as borax and sulphites.
While the cost of the nutrients in canned meats is generally much higher
than in fresh meats, the latter are not always easily obtained, or
capable of being kept for any length of time, and hence canned meats are
often indispensable.
CHAPTER IX
CEREALS
143. Preparation and Cost of Cereals.--The grains used in the
preparation of cereal foods are wheat, oats, corn, rice, and, to a less
extent, barley and rye. For some of these the entire cleaned grain is
ground or pulverized, while for others the bran and germ are first
removed. In order to improve their keeping qualities, they are often
sterilized before being put up in sealed packages. Special treatment, as
steaming or malting, is sometimes given to impart palatability and to
lessen the time required for cooking. As a class, the cereal foods are
clean, nutritious, and free from adulteration. Extravagant claims are
sometimes made as to their food value, and frequently excessive prices
are charged, out of proportion to the cost of the nutrients in the raw
material. Within recent years the number of cereal preparations has
greatly increased, due to improvements and variations in the methods of
manufacture.[56]
Cereal foods are less expensive than meats and the various animal food
products. They contain no refuse, are easily prepared for the table, and
may be kept without appreciable deterioration. Some of the
ready--to-eat brands are cooked, dried, and crushed, and sugar,
glucose, salt, and various condimental materials added to impart taste.
Others contain malt, or are subjected to a malting or germinating
process to develop the soluble carbohydrates, and such foods are
sometimes called predigested. It is believed that the cereals are being
more extensively used in the dietary, which is desirable both from an
economic and a nutritive point of view. Special care is necessary in the
cooking and preparation of cereals for the table, in order to develop
flavor and bring about hydration and rupturing of the tissues, as
explained in Chapter II.
144. Corn Preparations.--Corn or maize is characterized by a high
percent of fat and starch, and, compared with wheat and oats, a low
content of protein.[57] Removal of the bran and germ lessens the per
cent of fat. The germ is removed principally because it imparts poor
keeping qualities. Many of the corn breakfast foods contain 1 per cent
or less of fat and from 8 to 9 per cent of protein. Coarsely ground corn
foods are not as completely digested and assimilated as those more
finely ground. As in the case of wheat products, the presence of the
bran and germ appears to prevent the more complete absorption of the
nutrients. Finely ground corn meal compares favorably in digestibility
with wheat flour. Corn flour is prepared by removal of the bran and germ
and granulation of the more starchy portions of the kernel, and has
better keeping qualities than corn meal from which the bran and germ
have not been so completely removed. At times corn flour has been
sufficiently low in price to permit its use for the adulteration of
wheat flour. The mixing of corn and wheat flours, however, is prohibited
by law unless the product is so labeled. When combined with wheat flour,
corn bread and various other articles of food are prepared, but used
alone corn flour is not suitable for bread making, because its gluten
lacks the binding properties imparted to wheat flour by the gliadin. It
is essential that corn be used with foods of high protein content so as
to make a balanced ration; for when it forms a large part of the
dietary, the ration is apt to be deficient in protein. In a mixed
dietary, corn is one of the cheapest and best cereals that can be used.
Too frequently, however, excessive prices are charged for corn
preparations that contain no more nutrients than ordinary corn meal.
There is no difference between yellow and white corn meal so far as
nutritive value is concerned.
[Illustration: FIG. 31.--CORN STARCH.]
145. Oat Preparations are characterized by large amounts of both
protein and fat. Because of the removal of the hulls, they contain more
protein than the original grain. The oat preparations differ little in
chemical composition. They all have about 16 per cent of protein, 7 per
cent of fat, and 65 per cent of starch, and are richer in ash or mineral
matter than other cereals. The main difference is in method of
preparation and mechanical composition. Some are partially cooked and
then dried. Those costing 7 cents or more per pound do not contain any
greater amount of nutritive substance than those purchased in bulk at
about half the price. At one time it was believed that oats contained a
special alkaloid having a stimulating effect when fed to animals. Recent
investigations, however, show that there is no alkaloidal material in
oats, and whatever stimulating effect they may have results from the
nutrients they contain. Occasionally there is an appreciable amount of
cellulose, or fiber, left in the oat preparations, due to imperfect
milling. This noticeably lowers the digestibility. Oatmeal requires much
longer and more thorough cooking than many other cereals, and it is
frequently used as food when not well prepared. Digestion experiments
show that when oatmeal is cooked for four hours or more, it is more
readily acted upon by the diastase ferment and digested in a shorter
time than oatmeal cooked only a half hour.[5] Oatmeal is one of the
cheapest sources from which protein is obtained, and when well cooked it
can advantageously form an essential part of the ration. Unless
thoroughly cooked, the oat preparations do not appear to be quite so
completely or easily digested as some of the other cereals.
[Illustration: FIG. 32.--OAT STARCH GRANULES.]
[Illustration: FIG. 33.--WHEAT STARCH GRAINS.]
146. Wheat Preparations differ in chemical composition more than those
from oats or corn, because wheat is prepared in a greater variety of
ways. They are made either from the entire kernel, including the bran
and germ, or from special parts, as the granular middlings, as in the
case of some of the breakfast foods, and a few are made into a dough and
baked, then dried and toasted. Some special flours are advertised as
composed largely of gluten, but only those that have been prepared by
washing out the starch are entitled to be classed as gluten flours.[58]
For the food of persons suffering from diabetes mellitus physicians
advise the use of flour low in starch, and this can be made by washing
and thus removing a portion of the starch from wheat flour, as directed
in Experiment No. 30. The glutinous residue is then used for preparing
articles of food. Analyses of some of the so-called gluten flours show
that they contain no more gluten than ordinary flour, particularly the
low grades. A number of wheat breakfast foods are prepared by
sterilizing the flour middlings obtained after removal of the bran and
germ. These middlings are the same stock or material from which the
patent grades of flour are made, and they differ from wheat flour only
in mechanical structure and size of the particles. Where granular wheat
middlings can be secured in bulk at the same price as flour they furnish
a valuable and cheap cereal breakfast food.
As to the digestibility and food value, the wheat breakfast foods have
practically the same as graham, entire wheat, or ordinary patent flour,
depending upon the stock which they contain. Those with large amounts of
bran and germ are not as completely digested as when these parts of the
kernel are not included. Wheat preparations, next to oats, have the most
protein of any of the cereal foods. Occasionally they are prepared from
wheats low in gluten and not suitable for bread-making purposes. When
purchased in bulk the wheat preparations are among the cheapest foods
that can be used in the dietary.[56]
[Illustration: FIG. 34.--BARLEY STARCH.]
147. Barley Preparations are not so extensively used as wheat, oats,
and corn. Barley contains a little more protein than corn, but not quite
so much as wheat; otherwise it is quite similar to wheat in general
composition. Sometimes in the preparation of breakfast foods barley meal
is mixed with wheat or corn. Barley is supposed to be more readily
digested than some of the other cereals, because of the presence of
larger amounts of active ferment bodies, and it is frequently used for
making an extract known as "barley water," which, although it contains
very little nutritive value, as less than one per cent of the weight of
the barley is rendered soluble, is useful in its soothing influence and
mechanical action upon the mucous membrane of the digestive tract.
[Illustration: FIG. 35.--RICE STARCH.]
148. Rice Preparations.--Rice varies somewhat in composition, but
usually contains a slightly lower percentage of protein than corn and
also a smaller amount of fat. It is particularly rich in starch, and has
the least ash or mineral matter of any of the cereals. In order to make
a balanced ration, rice should be supplemented with legumes and other
foods rich in proteids. It is a valuable grain, but when used alone it
is deficient in protein. Rice is digested with moderate ease, but is not
as completely absorbed by the body as other cereals, particularly those
prepared by fine grinding or pulverization. Of late years rice culture
has been extensively introduced into some of the southern states, and
the domestic rice seems to have slightly higher protein content than the
imported. Rice contains less protein than other cereals, and the starch
grain is of different construction. Rice does not require such prolonged
cooking as oatmeal; it needs, however, to be thoroughly cooked.
149. Predigested Foods.[56]
"It is questionable whether it would be of advantage to a healthy
person to have his food artificially digested. The body under
normal conditions is well adapted to utilize such foods as the
ordinary mixed diet provides, among them the carbohydrates from the
cereals. Moreover, it is generally believed that for the digestive
organs, as for all others of the body, the amount of exercise they
are normally fitted to perform is an advantage rather than the
reverse. It has been said that 'a well man has no more need of
predigested food than a sound man has for crutches.' If the
digestive organs are out of order, it may be well to save them
work, but troubles of digestion are often very complicated affairs,
and the average person rarely has the knowledge needed to prescribe
for himself. In general, those who are well should do their own
work of digestion, and those who are ill should consult a competent
physician."--WOODS AND SNYDER.
150. The Value of Cereals in the Dietary.--Cereals are valuable in the
dietary because of the starch and protein they supply, and the heat and
energy they yield. They are among the most inexpensive of foods and,
when properly prepared, have a high degree of palatability; then, too,
they are capable of being blended in various ways with other foods. Some
are valuable for their mechanical action in digestion, rather than for
any large amount of nutrients. They do not furnish the quantity of
mineral matter and valuable phosphates that is popularly supposed. They
all contain from 0.5 to 1.5 percent of mineral matter, of which about
one third is phosphoric anhydrid. In discussing the phosphate content of
food, Hammersten states:[59]
"Very little is known in regard to the need of phosphates or
phosphoric acid.... The extent of this need is most difficult to
determine, as the body shows a strong tendency, when increased
amounts of phosphorus are introduced, to retain more than is
necessary. The need of phosphates is relatively smaller in adults
than in young developing animals."
In the coarser cereals, which include the bran and germ, there is the
maximum amount of mineral matter, but, as in the case of graham bread,
it is not as completely digested and absorbed by the body as the more
finely granulated products which contain less. The kind of cereal to use
in the dietary is largely a matter of personal choice. As only a small
amount is usually eaten at a meal, there is little difference in the
quantity of nutrients supplied by the various breakfast cereals.
TOTAL AND DIGESTIBLE NUTRIENTS AND FUEL VALUE OF CEREALS
[Transcriber's note: This table has been divided into two
parts to fit limits on page width.]
=======================================================
| TOTAL NUTRIENTS |
|-----+----+----+----------+----+
| | | | C.H. | |
KIND OF FOOD |Water|Pro.|Fat +----+-----+Ash |
| | | |N.F.|Fiber| |
| | | |Ext | | |
----------------------+-----+----+----+----+-----+----+
| % | % | % | % | % | % |
Oat Preparations: | | | | | | |
Oats, whole grain | 11.0|11.8| 5.0|59.7| 9.5| 3.0|
Oatmeal, raw | 7.3|16.1| 7.2|66.6| 9.9| 1.9|
Rolled, steam-cooked| 8.2|16.1| 7.4|65.2| 1.3| 1.8|
Wheat: | | | | | | |
Whole grain | 10.5|11.9| 2.1|71.9| 1.8| 1.8|
Cracked wheat | 10.1|11.1| 1.7|73.8| 1.7| 1.6|
Rolled, steam-cooked| 10.6|10.2| 1.8|74.4| 1.8| 1.5|
Shredded wheat | 8.1|10.6| 1.4|76.6| 2.1| 1.8|
Crumbed and malted | 5.6|12.2| 1.0|77.6| 1.7| 1.0|
Farina | 10.9|11.0| 1.4|75.9| 0.4| 0.4|
Rye: | | | | | | |
Whole grain | 11.6|10.6| 1.7|72.5| 1.7| 1.9|
Flaked, to be eaten | 11.1|10.0| 1.4| 75.8 | 1.7|
raw | | | | | | |
Barley: | | | | | | |
Whole grain | 10.9|12.4| 1.8|69.8| 2.7| 2.4|
Pearled barley | 11.5| 8.5| 1.1|77.5| 0.3| 1.1|
Buckwheat: | | | | | | |
Flour | 13.6| 6.4| 1.2|77.5| 0.4| 0.9|
Corn: | | | | | | |
Whole grain | 10.9|10.5| 5.4|69.6| 2.1| 1.5|
Corn meal, unbolted | 11.6| 8.4| 4.7| 74.0 | 1.3|
Corn meal, bolted | 12.5| 9.2| 1.9|74.4| 1.0| 1.0|
Hominy | 10.9| 8.6| 0.6|79.2| 0.4| 0.3|
Pop corn, popped | 4.3|10.7| 5.0|77.3| 1.4| 1.3|
Hulled corn | 74.1| 2.3| 0.9| 22.2 | 0.5|
Rice: | | | | | | |
Whole rice, polished| 12.3| 6.9| 0.3| 80.0 | 0.5|
Puffed rice | 7.1| 6.2| 0.6| 85.7 | 0.4|
Crackers | 6.8|10.7| 8.8|71.4| 0.5| 1.8|
Macaroni | 10.3|13.4| 0.9| 74.1 | 1.3|
=======================================================
=================================================
| DIGESTIBLE NUTRIENTS
|----+----+----+----+------
| | | | | Fuel
KIND OF FOOD |Pro.|Fat |C.H.|Ash | Value
| | | | | per lb.
| | | | |
----------------------+----+----+----+----+----------
| % | % | % | % | Calories.
Oat Preparations: | | | | |
Oats, whole grain | -- | -- | -- | -- | --
Oatmeal, raw |12.5| 6.5|65.5| 1.4| 1767
Rolled, steam-cooked|12.5| 6.7|64.5| 1.4| 1759
Wheat: | | | | |
Whole grain | -- | -- | -- | -- | --
Cracked wheat | 8.1| 1.5|68.7| 1.2| 1501
Rolled, steam-cooked| 8.5| 1.6|70.7| 1.1| 1541
Shredded wheat | 7.7| 1.3|71.1| 1.4| 1521
Crumbed and malted | 9.1| 0.9|73.7| 1.4| 1623
Farina | 8.9| 1.3|72.9| 0.5| 1609
Rye: | | | | |
Whole grain | -- | -- | -- | -- | --
Flaked, to be eaten | 7.8| 1.3|71.1| 1.3| 1516
raw | | | | |
Barley: | | | | |
Whole grain | -- | -- | -- | -- | --
Pearled barley | 6.6| 1.0|73.0| 0.3| 1514
Buckwheat: | | | | |
Flour | 5.0| 1.1|73.1| 0.7| 1471
Corn: | | | | |
Whole grain | -- | -- | -- | -- | --
Corn meal, unbolted | 6.2| 4.2|73.2| 1.0| 1728
Corn meal, bolted | 6.8| 1.7|74.6| 0.8| 1602
Hominy | 6.4| 0.5|78.7| 0.2| 1671
Pop corn, popped | 7.9| 4.5|77.8| 1.0| 1882
Hulled corn | 1.7| 0.8|21.8| 0.4| 492
Rice: | | | | |
Whole rice, polished| 5.8| 0.3|78.4| 0.4| 1546
Puffed rice | 5.1| 0.5|84.0| 0.3| 1639
Crackers | 9.1| 7.9|70.5| 1.4| 1905
Macaroni |11.6| 0.8|72.2| 1.0| 1660
=================================================
CHAPTER X
WHEAT FLOUR
151. Use for Bread Making.--Wheat is particularly adapted to
bread-making purposes because of the physical properties of the gliadin,
one of its proteids. It is the gliadin which, when wet, binds together
the flour particles, enabling the gas generated during bread making to
be retained, and the loaf to expand and become porous. Wheat varies in
chemical composition between wide limits; it may contain as high as 16
per cent of protein, or as low as 8 per cent; average wheat has from 12
to 14 per cent; and with these differences in composition, the
bread-making value varies.
[Illustration: FIG. 36.--STARCHY (LIGHT-COLORED) AND
GLUTINOUS (DARK-COLORED) WHEATS.]
152. Winter and Spring Wheat Flours.--There are two general classes of
wheat: spring wheat and winter wheat. The winter varieties are seeded in
the fall, and the spring varieties, which are grown mainly in the
Northwestern states, Minnesota, and North and South Dakota, and the
Canadian Northwest, are seeded in the spring and mature in the late
summer. Winter wheat is confined to more southern latitudes and regions
of less severe winter, and matures in the early summer. There are many
varieties of both spring and winter wheat, although wheats are
popularly characterized only as hard or soft, depending upon the
physical properties. The winter wheats are, as a rule, more soft and
starchy than the spring wheats, which are usually corneous or flinty to
different degrees. There is a general tendency for wheats to become
either starchy or glutinous, owing to inherited individuality of the
seed and to environment. There are often found in the same field wheat
plants yielding hard glutinous kernels, and other plants producing
starchy kernels containing 5 per cent less proteids. Wheats of low
protein content do not make high-grade flour; neither do wheats of the
maximum protein content necessarily make the best flour. For a more
extended discussion of wheat proteids, the student is referred to
Chapter XI.
[Illustration: FIG. 37.--LONGITUDINAL SECTION OF WHEAT KERNEL:
_a_, pericarp; _b_, bran layers; _c_, aleurone cells; _d_,
germ. (After KÖNIG.)]
153. Composition of Wheat and Flour.--In addition to 12 to 14 per cent
proteids, wheat contains 72 to 76 per cent of starch and small amounts
of other carbohydrates, as sucrose, dextrose, and invert sugar. The ash
or mineral matter ranges from 1.7 to 2.3 per cent. There is also about 2
per cent fiber, 2.25 per cent ether extract or crude fat, and about 0.2
per cent organic acids.
Summary:
COMPOSITION OF WHEAT FLOUR
========================================================
| Per Cent
Water | 12.00
|
{Potash } |
{Soda } |
{Lime } |
Ash {Magnesia } | 2.25
{Phosphoric anhydrid} |
{Sulphuric anhydrid } |
{Other substances } |
|
{Albumin 0.4} |
{Globulin 0.9} |
Protein {Gliadin 6.0} | 13.00
{Glutenin 5.3} |
{Other proteids 0.4} |
Other nitrogenous bodies, as amids, lecethin | 0.25
Crude fat, ether extract | 2.25
Cellulose | 2.25
Starch | 66.00
Sucrose, dextrose, soluble carbohydrates, etc.| 2.00
=======================================================
154. Roller Process of Flour Milling.--Flours vary in composition,
food value, and bread-making qualities with the character of the wheat
and the process of milling employed. Prior to 1870 practically all
wheat flour was prepared by grinding the wheat between millstones; but
with the introduction of the roller process, steel rolls were
substituted for millstones.[60] By the former process a smaller amount
of flour was secured from the wheat, but with the present improved
systems about 75 per cent of the weight of the grain is recovered as
merchantable flour and 25 per cent as wheat offals, bran, and
shorts[61].
[Illustration: FIG. 38.--GRANULAR WHEAT FLOUR PARTICLES.]
The wheat is first screened and cleaned, then passed on to the
corrugated rolls, or the first break, where it is partially flattened
and slightly crushed and a small amount of flour, known as the break
flour, is separated by means of sieves, while the main portion is
conveyed through elevators to the second break, where the kernels are
more completely flattened and the granular flour particles are partially
separated from the bran. The material passes over several pairs of rolls
or breaks, each succeeding pair being set a little nearer together. This
is called the gradual reduction process, because the wheat is not made
into flour in one operation. More complete removal of the bran and other
impurities from the middlings is effected by means of sieves,
aspirators, and other devices, and the purified middlings are then
passed on to smooth rolls, where the granulation is completed. The flour
finally passes through silk bolting cloths, containing upwards of 12,000
meshes per square inch. The dust and fine débris particles are removed
at various points in the process. The granulation of the middlings is
done after the impurities are removed, the object being first to
separate as perfectly as possible the middlings from the branny portions
of the kernel. If the wheat were first ground into a fine meal, it would
be impossible to secure complete separation of the flour from the
offal portions of the kernel.
[Illustration: FIG. 39.--EXTERIOR OF FLOUR MILL AND WHEAT ELEVATOR.]
Flour milling is entirely a mechanical process; the flour stock passes
from roll to roll by means of elevators. According to the number of
reductions which the middlings and stock undergo, the milling is
designated as a long or a short reduction system; the term 4, 6, 8, or
10 break process means that the stock has been subjected to that number
of reductions. With an 8-break system of milling, the process is more
gradual than with a 4-break, and greater opportunity is afforded for
complete removal of the bran. In some large flour mills, the wheat is
separated into forty or more different products, or streams, as they are
called, so as to secure a better granulation and more complete removal
of the offals, after which many of these streams are brought together to
form the finished flour. What is known as patent flour is derived from
the reduction of the middlings, while the break flours are recovered
before the offals are completely removed; hence they are not of so high
a grade. No absolute definition can be given, however, of the term
"patent flour," as usage varies the meaning in different parts of the
country.
155. Grades of Flour.--Flour is the purified, refined, and bolted
product obtained by reduction and granulation of wheat during and after
the removal of the branny portions of the wheat kernel. It is defined by
proclamation of the Secretary of Agriculture, under authority of an
act of Congress, as: "Flour is the fine, sound product made by bolting
wheat meal, and contains not more than thirteen and one half (13.5) per
cent of moisture, not less than one and twenty-five hundredths (1.25)
per cent of nitrogen, not more than one (1) per cent of ash, and not
more than fifty hundredths (0.50) per cent of fiber."
[Illustration: FIG. 40.--GRINDING FLOOR OF FLOUR MILL,
RUSSELL-MILLER MILLING CO., MINNEAPOLIS, MINN.]
Generally speaking, flour may be divided into two classes, high grade
and low grade. To the first class belong the first and second patents
and, according to some authorities, a portion of the straight grade, or
standard patent flour, and to the second class belong the second clear
and "red dog." About 72 per cent of the cleaned wheat as milled is
recovered in the higher grades of flour, and about 2 or 3 per cent as
low grades, a large portion of which is sold as animal food. The high
grades are characterized by a lighter color, more elastic gluten, better
granulation, and a smaller number of débris particles. Although the
lower grade flours contain a somewhat higher percentage of protein, they
are not as valuable for bread-making purposes because the gluten is not
as elastic, and consequently they do not make as good bread. If the
impurities from the low grades could be further eliminated, it is
believed that less difference would exist between high and low grade
flours.
Various trade names are used to designate flours, as a 95 per cent
patent, meaning that 95 per cent of the total flour is included in the
patent; or an 85 per cent patent, when 85 per cent of all the flour is
included in that particular patent. If all the flour streams were
purified and blended, and only one grade of flour made, it would be
called a 100 per cent patent. An 85 per cent patent is a higher grade
flour than a 95 per cent patent.
[Illustration: FIG. 41.--SILK BOLTING CLOTH USED IN
MANUFACTURE OF FLOUR, MAGNIFIED.]
156. Composition of Flour.--The composition of the different grades of
flour made from the same wheat is given in the following table:[62]
COMPOSITION, ACIDITY, AND HEATS OF COMBUSTION OF FLOURS AND OTHER
MILLED PRODUCTS OF WHEAT
===========================================================================
|WATER| PROTEIN | FAT| CARBO-| ASH| ACIDITY | HEAT OF
MILLED PRODUCT | |(N × 5.7)| | HY- | | CALCUL- |COMBUSTION
| | | | DRATES| |ATED AS | PER GRAM
| | | | | |LACTIC |DETERMINED
| | | | | | ACID |
---------------------------------------------------------------------------
| % | % | % | % | % | % |Calories
First patent flour |10.55| 11.08 |1.15| 76.85 |0.37| 0.08 | 4032
Second patent flour |10.49| 11.14 |1.20| 76.75 |0.42| 0.08 | 4006
Straight[A] or | | | | | | |
standard patent |10.54| 11.99 |1.61| 75.36 |0.50| 0.09 | 4050
flour | | | | | | |
First clear grade |10.13| 13.74 |2.20| 73.13 |0.80| 0.12 | 4097
flour | | | | | | |
Second clear grade |10.08| 15.03 |3.77| 69.37 |1.75| 0.56 | 4267
flour | | | | | | |
"Red dog" flour | 9.17| 18.98 |7.00| 61.37 |3.48| 0.59 | 4485
Shorts | 8.73| 14.87 |6.37| 65.47 |4.56| 0.14 | 4414
Bran | 9.99| 14.02 |4.39| 65.54 |6.06| 0.23 | 4198
Entire-wheat flour |10.81| 12.26 |2.24| 73.67 |1.02| 0.32 | 4032
Graham flour | 8.61| 12.65 |2.44| 74.58 |1.72| 0.18 | 4148
Wheat | 8.50| 12.65 |2.36| 74.69 |1.80| 0.18 | 4140
===========================================================================
[Footnote A: Straight flour includes the first and second patents and
first clear grade.]
In the table it will be noted that there is a gradual increase in
protein content from first patent to "red dog," the largest amount being
in the "red dog" flour. Although "red dog" contains the most protein, it
is by far the poorest flour in bread-making qualities, and in the
milling of wheat often it is not separated from the offals, but is sold
as an animal food. It will also be seen that there is a gradual increase
in the ash content from the highest to the lowest grades of flour, the
increase being practically proportional to the grade,--the most ash
being in the lowest grade. The grade to which a flour belongs can be
determined more accurately from the ash content than from any other
constituent. Patent grades of flour rarely contain more than 0.55 per
cent of ash,--the better grades less than 0.5 per cent. The more
completely the bran and offals are removed during the process of
milling, the lower the per cent of ash. The ash content, however, cannot
be taken as an absolute guide in all cases, as noticeable variations
occur in the amount of mineral matter or ash in different wheats;
starchy wheats that have reached full maturity often contain less than
hard wheats grown upon rich soil where the growing season has been
short, and from such wheats a soft, straight flour may have as low a per
cent of ash as a hard first patent flour. When only straight or standard
patent flour is manufactured by a mill, all of the flour is included
which would otherwise be designated first and second patents and first
clear.
157. Graham and Entire Wheat Flours.--When the germ and a portion of
the bran are retained in the flour, and the particles are not completely
reduced, the product is called "entire wheat flour." The name does not
accurately describe the product, as it includes all of the flour and
only a portion of the bran, and not the entire wheat kernel. Graham
flour is coarsely granulated wheat meal. No sieves or bolting cloths
are employed in its manufacture, and many coarse, unpulverized
particles are present in the product[62].
158. Composition of Wheat Offals.--Bran and shorts are characterized
by a high percentage of fiber, or cellulose. The ash, fat, and protein
content of bran are all larger than of flour. The protein, however, is
not in the form of gluten, but is largely albumin and globulins,[16]
which are mainly in the aleurone layer of the wheat kernel, and are
inclosed in branny capsules, and consequently are in a form not readily
digested by man.
[Illustration: FIG. 42.--FLOUR AND GLUTEN.
1, flour; 2, dough; 3, moist gluten; 4, dry gluten.]
The germ is generally included in the shorts, although occasionally it
is removed for special commercial purposes. It is sometimes sterilized
and used in breakfast food products. The germ is rich in oil and is
excluded from the flour mainly because it has a tendency to become
rancid and to impart to the flour poor keeping qualities. Wheat oil has
cathartic properties, and it is believed the physiological action of
whole wheat and graham bread is in part due to the oil. The germ is also
rich in protein, mainly in the form of globulins and proteoses. A dough
cannot be made of pure germ, because it contains so little of the
gliadin and glutenin.
159. Aging and Curing of Flour.--Flours well milled and made from
high-grade, cleaned wheat generally improve in bread-making value when
stored in clean, ventilated warehouses for periods of three to six
months[9]. High-grade flour becomes drier and whiter and produces bread
of slightly better quality when properly cured by storage. If the flour
is in any way unsound, it deteriorates during storage, due to the action
of ferment bodies. Wheat also, when properly cleaned and stored,
improves in milling and bread-making value. Certain enzymic changes
appear to take place which are beneficial. Wheats differ materially from
year to year in bread-making value, and those produced in seasons when
all the conditions for crop growth are normal do not seem to be so much
improved by storing and aging, either of the wheat or the flour, as when
the growing season has been unfavorable. When wheat is stored, specific
changes occur in both the germ and the cells of the kernel; these
changes are akin to the ripening process, and appear to be greater if,
for any reason, the wheat has failed to fully mature or is abnormal in
composition.
The flour yield of wheat is in general proportional to the weight per
bushel of the grain, well-filled, heavy grain producing more flour than
light grain.[61] The quality of the flour, however, is not necessarily
proportional to the weight of the grain. It is often necessary to blend
different grades and types of wheat in order to secure good flour.
160. Macaroni Flour is made from durum wheat, according to Saunders a
variety of hard, spring wheat. It is best grown in regions of restricted
rainfall. Durum and other varieties of hard spring wheat grown under
similar conditions, differ but little in general chemical composition,
except that the gluten of durum appears to have a different percentage
of gliadin and glutenin, and the flour has a more decided yellow color.
Durum wheats are not generally considered as valuable for bread making
as other hard wheat. They differ widely in bread-making value, some
being very poor, while others produce bread of fair quality.[68]
161. Color.--The highest grades of flour are white in color, or of a
slight creamy tinge. Dark-colored, slaty, and gray flours are of
inferior quality, indicating a poor grade of wheat, poor milling, or a
poor quality of gluten. Flours, after being on the market for a time,
bleach a little and improve to a slight degree in color. Color is one of
the characteristics by which the commercial value of flour is
determined; the whiter the flour, the better the grade, provided other
properties are equal[9]. The color, however, should be a pure or cream
white. Some flours have what is called a dead white color, and, while
not objectionable as far as color is concerned, they are not as valuable
for bread-making and general commercial purposes. One of the principal
trade requirements of a flour is that it possess a certain degree of
whiteness and none of the objectionable shades mentioned.
To determine the color of a flour, it is compared with a standard. If it
is a winter wheat flour, one of the best high-grade winter patents to be
found on the market is selected, and the sample in question is compared
with this; if it is a spring wheat patent flour, one of the best spring
wheat patent grades is taken as the standard. In making the comparison,
the flours should be placed side by side on a glass plate and smoothed
with the flour trier, the comparison being made preferably by a north
window. Much experience and practice are necessary in order to determine
with accuracy the color value of a flour.
162. Granulation.--The best patent grades of flour contain an
appreciable amount of granular middlings, which have a characteristic
"feel" similar to fine, sharp sand. A flour which has no granular
feeling is not usually considered of the highest grade, but is generally
a soft wheat flour of poor gluten. However, a flour should not be too
coarsely granulated. The percentage amounts of the different grades of
stock in a flour can be approximately determined by means of sieves and
different sized bolting cloths. To test a flour, ten grams are placed in
a sieve containing a No. 10 bolting cloth; with a camel's-hair brush and
proper manipulation, the flour is sieved, and that which passes through
is weighed. The percentage amount remaining on the No. 10 cloth is
coarser middlings. Nearly all high-grade flours leave no residue on the
No. 10 cloth. The sifted flour from the No. 10 cloth is also passed
through Nos. 11, 12, 13, and 14 cloths[63]. In this way the approximate
granulation of any grade of flour may be determined, and the granulation
of an unknown sample be compared with that of a standard flour. In
determining the granulation of a flour, if there are any coarse or
discolored particles of bran or dust, they should be noted, as it is an
indication of poor milling. When the flour is smoothed with a trier,
there should be no channels formed on the surface of the flour, due to
fibrous impurities caught under the edge of the trier. A hand magnifying
glass is useful for detecting the presence of abnormal amounts of dirt
or fibrous matter in the flour.
163. Capacity of Flour to absorb Water.--The capacity of a flour to
absorb water is determined by adding water from a burette to a weighed
amount of flour until a dough of standard consistency is obtained. Low
absorption is due to low gluten content. A good flour should absorb from
60 to 65 per cent of its weight of water. In making the test, it is
advisable to determine the absorption of a flour of known baking value
at the same time that an unknown flour is being tested. Flours of low
absorption do not make breads of the best quality; also there are a
smaller number of loaves per barrel, and the bread dries out more
readily.
164. Physical Properties of Gluten.--The percentages of wet and dry
gluten in a flour are determined as outlined in Experiment No. 27.
Flours of good character should show at least 30 per cent moist gluten
and from 10 to 12 per cent dry gluten. The quality of a flour is not
necessarily proportional to its gluten content, although a flour with
less than 10-1/2 per cent of dry gluten will not make the best quality
of bread, and flours with excessive amounts are sometimes poor bread
makers. The color of the gluten is also important; it should be white or
creamy. The statements made in regard to color of flour apply also to
color of the gluten. A dark, stringy, or putty-like gluten is of little
value for bread-making purposes.[64] In making the gluten test, it is
advisable to compare the gluten with that from a flour of known
bread-making value. Soft wheat flours have a gluten of different
character from hard wheat flours.
165. Gluten as a Factor in Bread Making.--The bread-making value of a
flour is dependent upon the character of the wheat and the method of
milling. It is not necessarily dependent upon the amount of gluten, as
the largest volume and best quality of bread are often made from flour
of average rather than maximum gluten content. But flours with low
gluten do not produce high-grade breads. When a flour contains more than
12 or 13 per cent of proteids, any increase does not necessarily mean
added bread-making value. The quality of the gluten, equally with the
amount, determines the value for bread-making purposes.
166. Unsoundness.--A flour with more than 14 per cent of moisture is
liable to become unsound. High acidity also is an indication of
unsoundness or of poor keeping qualities. The odor of a sample of flour
should always be carefully noted, for any suggestion of fermentation
sufficient to affect the odor renders the flour unsuited for making the
best bread. Any abnormal odor in flour is objectionable, as it is due to
contamination of some sort, and most frequently to fermentation changes.
A musty odor is always an indication of unsoundness. Some flours which
have but a slight suggestion of mustiness will, when baked into bread,
have it more pronounced; on the other hand, some odors are removed
during bread making. Flours may absorb odors because of being stored in
contaminated places or being shipped in cars in which oil or other
ill-smelling products with strong odors have previously been shipped.
Unsoundness is often due to faulty methods in handling, as well as to
poor wheat, or to lack of proper cleaning of the wheat or flour.
[Illustration: FIG. 43.--FUNGOUS GROWTH IN UNSOUND FLOUR.]
167. Comparative Baking Tests.--To determine the bread-making value of
a flour, comparative baking tests, as outlined in Experiment No. 29, are
made; the flour in question is thus compared as to bread-making value
with a flour of known baking quality. In making the baking tests, the
absorption of the flour, the way in which it responds in the doughing
process, and the general properties of the dough, are noted. The details
should be carried out with care, the comparison always being made with a
similar flour of known baking value, and the bread should be baked at
the same time and under the same conditions as the standard. The color
of the bread, the size and weight of the loaf, and its texture and odor,
are the principal characteristics to be noted.
[Illustration: FIG. 44.--COMPARATIVE BAKING TESTS.]
The quality of flour for bread-making purposes is not strictly
dependent upon any one factor, but appears to be the aggregate of a
number of desirable characteristics. The commercial grade of a flour can
be accurately determined from the color, granulation, absorption, gluten
and ash content, and the quality of the bread. Technical flour testing
requires much experience and a high degree of skill.
168. Bleaching.--In the process of manufacture, flours are often
subjected to air containing traces of nitrogen peroxide gas, generated
by electrical action and resulting in the union of the oxygen and
nitrogen of the air. This whitens and improves the color of the flour.
Bleached flours differ neither in chemical composition nor in nutritive
value from unbleached flours, except that bleached flours contain a
small amount (about one part to one million parts of flour) of nitrite
reacting material, which is removed during the process of bread making.
The amount of nitrites produced in flour during bleaching is less than
is normally present in the saliva, or is found naturally in many
vegetable foods, or in smoked or cured meats, or in bread made from
unbleached flour and baked in a gas oven where nitrites are produced
from combustion of the gas. The bleaching of flour cannot be regarded as
in any way injurious to health or as adulteration, and a bleached flour
which has good gluten and bread-making qualities is entirely
satisfactory. It is not possible to successfully bleach low-grade flours
so they will resemble the high grades, because the bran impurities of
the low grades blacken during bleaching and become more prominent.
Alway, of the Nebraska Experiment Station, has shown that there is no
danger to apprehend from over-bleaching, for when excess of the
bleaching reagent is used, flours become yellow in color[65]. Similar
results have been obtained at the Minnesota Experiment Station. As
bleaching is not injurious to health, and as it is not possible through
bleaching to change low grades so as to resemble the patent grades,
bleaching resolves itself entirely into the question of what color of
flour the consumer desires. Pending the settlement of the status of
bleaching the practice has been largely discontinued.
[Illustration: FIG. 45.--WHEAT HAIRS AND DÉBRIS IN LOW GRADE FLOURS.]
169. Adulteration of Flour.--Flour is not easily adulterated, as the
addition of any foreign material interferes with the expansion and
bread-making qualities and hence is readily detected. The mixing of
other cereals, as corn flour, with wheat flour has been attempted at
various times when wheat commanded a high price, but this also is
readily detected, by microscopic examination, as the corn starch and
wheat starch grains are quite different in mechanical structure. Such
flours are required to be labeled, in accord with the congressional act
of 1898, when Congress passed, in advance of the general pure food bill,
an act regulating the labeling and sale of mixed and adulterated flours.
Various statements have been made in regard to the adulteration of flour
with minerals, as chalk and barytes, but such adulteration does not
appear to be at all general.
170. Nutritive Value of Flour.--From a nutritive point of view, wheat
flour and wheat bread have a high value.[66] A larger amount of
nutrients can be secured for a given sum of money in the form of flour
than of any other food material except corn meal. According to
statistics, the average per capita consumption of wheat in the United
States is about 4-1/2 bushels, or, approximately, one barrel per year,
and from recent investigations it would appear that the amount of flour
used in the dietary is on the increase. According to the Bureau of
Labor, flour costs the average laborer about one tenth as much as all
other foods combined, although he secures from it a proportionally
larger amount of nutritive material than from any other food.
CHAPTER XI
BREAD AND BREAD MAKING
171. Leavened and Unleavened Bread.--To make unleavened bread the
flour is moistened and worked into a stiff dough, which is then rolled
thin, cut into various shapes, and baked, forming a brittle biscuit or
cracker.
The process of making raised or leavened bread consists, in brief, of
mixing the flour and water in proper proportions for a stiff dough,
together with some salt for seasoning, and yeast (or other agent) for
leavening. The moistened gluten of the flour forms a viscid, elastic,
tenacious mass, which is thoroughly kneaded to distribute the yeast. The
dough is then set in a warm place and the yeast begins to grow, or
"work," causing alcoholic fermentation, with the production of carbon
dioxid gas, which expands the dough, or causes it to "rise," thus
rendering it porous. After the yeast has grown sufficiently, the dough
is baked in a hot oven, where further fermentation is stopped because of
destruction of the yeast by the heat, which also causes the gas to
expand the loaf and, in addition, generates steam. The gas and steam
inflate the tenacious dough and finally escape into the oven. At the
same time the gluten of the dough is hardened by the heat, and the mass
remains porous and light, while the outer surface is darkened and formed
into a crust.
When the flour is of good quality, the dough well prepared, and the
bread properly baked, the loaf has certain definite characteristics. It
should be well raised and have a thin, flinty crust, which is not too
dark in color nor too tough, but which cracks when broken; the crumb, as
the interior of the loaf is called, should be porous, elastic, and of
uniform texture, without large holes, and should have good flavor, odor,
and color.
Meal or flour from any of the cereals may be used for unleavened bread,
but leavened bread can be made only from those that contain gluten, a
mixture of vegetable proteids which when moistened with water becomes
viscid, and is tenacious enough to confine the gas produced in the
dough. Most cereals, as barley, rice, oats, and corn, some of which are
very frequently made into forms of unleavened bread, are deficient or
wholly lacking in gluten, and hence cannot be used alone for making
leavened bread. For the leavened bread, wheat and rye, which contain an
abundance of gluten, are best fitted, wheat being in this country by far
the more commonly used.
172. Changes during Bread Making.--In bread making complex physical,
chemical, and biological changes occur. Each chemical compound of the
flour undergoes some change during the process. The most important
changes are as follows[64]:
1. Production of carbon dioxid gas, alcohol, and soluble carbohydrates
as the result of ferment action.
2. Partial rupturing of the starch grains and formation of a small
amount of soluble carbohydrates due to the action of heat.
3. Production of lactic and other organic acids.
4. Formation of volatile carbon compounds, other than alcohol and carbon
dioxid.
5. Change in the solubility of the gluten proteins, due to the action of
the organic acids and fermentation.
6. Changes in the solubility of the proteids due to the action of heat,
as coagulation of the albumin and globulin.
7. Formation and liberation of a small amount of volatile, nitrogenous
compounds, as ammonia and amids.
8. Partial oxidation of the fat.
173. Loss of Dry Matter during Bread Making.--As many of the compounds
formed during bread making are gases resulting from fermentation action,
and as these are volatile at the temperature of baking, appreciable
losses necessarily take place. Experiments show about 2 per cent of loss
of dry matter under ordinary conditions. These losses are not confined
to the carbohydrates alone, but also extend to the proteids and other
compounds. When 100 pounds of flour containing 10 per cent of water and
90 per cent of dry matter are made into bread, the bread contains about
88 pounds of dry matter. In exceptional cases, where there has been
prolonged fermentation, the losses exceed 2 per cent[64].
[Illustration: FIG. 46.--BREWERS' YEAST.]
174. Action of Yeast.--Yeast is a monocellular plant requiring sugar
and other food materials for its nourishment. Under favorable conditions
it rapidly increases by budding, and as a result produces the well-known
alcoholic fermentation. It requires mineral food, as do plants of a
higher order, and oftentimes the fermentation process is checked for
want of sufficient soluble mineral food. The yeast plant causes a
number of chemical changes to take place, as conversion of starch to a
soluble form and alcoholic fermentation.
C_{6}H_{10}O_{5} + H_{2}O = C_{6}H_{12}O_{6}.
C_{6}H_{12}O_{6} = 2 C_{2}H_{5}OH + 2 CO_{2}.
Alcoholic fermentation cannot occur until the starch has been converted
into dextrose sugar. The yeast plant is destroyed at a temperature of
131° F. It is most active from 70° to 90° F. At a low temperature it is
less active, and when it freezes the cells are ruptured. A number of
different kinds of fermentation are associated with the growth of the
yeast plant, and there are many varieties of yeast, some of which are
more active than others. For bread making an active yeast is desirable
to prevent the formation of acid bodies. If the work proceeds quickly,
the rising process is completed before the acid fermentation is far
advanced. If fermentation is too prolonged, some of the products of the
yeast plant impart an undesirable taste and odor to the bread, and
hinder the development of the gluten and expansion of the loaf.
175. Compressed Yeast.--The yeast most commonly used in bread making
is compressed yeast, a product of distilleries. The yeast floating on
the surface of the wort is skimmed off and that remaining is allowed to
settle to the bottom, and is obtained by running the wort into shallow
tanks or settling trays. It is then washed with cold water, and the
impurities are removed either by sieving through silk or wire sieves,
or, during the washing, by fractional precipitation. The yeast is then
pressed, cut into cakes, and wrapped in tinfoil. When fresh, it is of
uniform creamy color, moist, and of a firm, even texture[18]. It should
be kept cold, as it readily decomposes.
176. Dry Yeast is made by mixing starch or meal with fresh yeast until
a stiff dough is formed. This is then dried, either in the sun or at a
moderate temperature, and cut into cakes. By drying, many of the yeast
cells are rendered temporarily inactive, and so it is a slower acting
leaven than the compressed yeast. A dry yeast will keep indefinitely.
177. Production of Carbon Dioxid Gas and Alcohol.--Carbon dioxid and
alcohol are produced in the largest amounts of any of the compounds
formed during bread making. When the alcoholic ferments secreted by the
yeast plant act upon the invert sugars and produce alcoholic
fermentation, carbon dioxid is one of the products formed. Ordinarily
about 1 per cent of carbon dioxid gas is generated and lost during bread
making. About equal weights of carbon dioxid and alcohol are produced
during the fermentation. In baking, the alcohol is vaporized and aids
the carbon dioxid in expanding the dough and making the bread porous. If
all of the moisture given off during bread making be collected it will
be found that from a pound loaf of bread there are about 40 cubic
centimeters of liquid; when this is submitted to chemical analysis,
small amounts of alcohol are obtained. Alcoholic fermentation sometimes
fails to take place readily, because there are not sufficient soluble
carbohydrates to undergo inversion, or other food for the yeast plant.
Starch cannot be converted directly into alcohol and carbon dioxid gas;
it must first be changed into dextrose sugars, and these undergo
alcoholic fermentation. Bread gives no appreciable reaction for alcohol
even when fresh.[64]
[Illustration: FIG. 47.--WHEAT STARCH GRANULES AFTER
FERMENTATION WITH YEAST, AS IN BREAD MAKING.]
If the gluten is of poor quality, or deficient in either gliadin or
glutenin, the dough mass fails to properly expand because the gas is not
all retained. The amount of gas formed is dependent upon temperature,
rapidity of the ferment action, and quality of the yeast and flour. If
the yeast is inactive, other forms of fermentation than the alcoholic
may take place and, as a result, the dough does not expand. Poor yeast
is a frequent cause of poor bread.
The temperature reached in bread making is not sufficient to destroy all
the ferment bodies associated with the yeast, as, for example, bread
sometimes becomes soft and stringy, due to fermentation changes after
the bread has been baked and stored. Both bread and flour are subject to
many bacterial diseases, and one of the objects of thorough cleaning of
the wheat and removal of the bran and débris particles during the
process of flour manufacture is to completely eliminate all ferment
bodies mechanically associated with the exterior of the wheat kernel,
which, if retained in the flour, would cause it readily to become
unsound.
178. Production of Soluble Carbohydrates.--Flour contains naturally a
small amount of soluble carbohydrates, which are readily acted upon by
the alcoholic ferments. The yeast plant secretes soluble ferments, which
act upon the starch, forming soluble carbohydrates, and the heat during
baking brings about similar changes. In fact, soluble carbohydrates are
both consumed and produced by ferment action during the bread-making
process. Flour contains, on an average, 65 per cent of starch, and
during bread making about 10 per cent is changed to soluble forms.
Bread, on a dry matter basis, contains approximately 6 per cent of
soluble carbohydrates, including dextrine, dextrose, and sucrose
sugars.[64]
The physical changes which the starch grains undergo are also
noticeable. Wheat starch has the structure shown in illustration No. 33.
The starch grains are circular bodies, concave, with slight markings in
the form of concentric rings. When the proteid matter of bread is
extracted with alcohol and the starch grains are examined, it will, be
seen that some of them are partially ruptured, like those in popped
corn, while others have been slightly acted upon or eaten away by the
organized ferments, the surface of the starch grains being pitted, as
shown in the illustration. The joint action of heat and ferments on the
starch grains changes them physically so they may more readily undergo
digestion. The brown coating or crust formed upon the surface of bread
is mainly dextrine, produced by the action of heat on the starch.
Dextrine is a soluble carbohydrate, having the same general composition
as starch, but differing from it in physical properties and ease of
digestion.
179. Production of Acids in Bread Making.--Wheat bread made with yeast
gives an acid reaction. The acid is produced from the carbohydrates by
ferment action. Flour contains about one tenth of 1 per cent of acid;
the dough contains from 0.3 to 0.5 per cent, while the baked bread
contains from 0.14 to 0.3 per cent, but after two or three days slightly
more acid is developed.[64] During the process of bread making, a small
portion of the acid is volatilized, but the larger part enters into
chemical combination with the gliadin, forming an acid proteid. When the
alcoholic fermentation of bread making becomes less active, acid
fermentations begin, and sour dough results. It is not definitely known
what specific organic acids are developed in bread making. Lactic and
butyric acids are known to be formed, and for purposes of calculation,
the total acidity is expressed in terms of lactic acid.
The acidity is determined by weighing 20 grams of flour into a flask,
adding 200 cubic centimeters of distilled water, shaking vigorously, and
leaving the flour in contact with the water for an hour; 50 cubic
centimeters of the filtered solution are then titrated with a tenth
normal solution of potassium hydroxid. Phenolphthalein is used as the
indicator. It cannot be said that all of the alkali is used for
neutralizing the acid, as a portion enters into chemical combination
with the proteids. If the method for determining the acid be varied,
constant results are not secured. Unsound or musty flours usually show a
high per cent of acidity.
[Illustration: FIG. 48.--APPARATUS USED IN STUDY OF LOSSES
IN BREAD MAKING.]
180. Volatile Compounds produced during Bread Making.--In addition to
carbon dioxid and alcohol, there is lost during bread making a small
amount of carbon in other forms, as volatile acids and hydrocarbon
products equivalent to about one tenth of one per cent of carbon dioxid.
The aroma of freshly baked bread is due to these compounds. Both the
odor and flavor of bread are caused in part by the volatile acids and
hydrocarbons. The amount and kind of volatile products formed can be
somewhat regulated through the fermentation process by the use of
special flours and the addition of materials that produce specific
fermentation changes and desirable aromatic compounds. Some of the
ferment bodies left in flour from the imperfect removal of the dirt
adhering to the exterior of the wheat kernels impart characteristic
flavors to the bread. The so-called nutty flavor of some bread is due to
the action of these ferment bodies and, when intensified, it becomes
objectionable. Fungous growths in unsound flour and bread result in the
liberation of volatile products, which impart a musty odor. Good odor
and flavor are very desirable in both flour and bread.
181. Behavior of Wheat Proteids in Bread Making.--Gluten is an
ingredient of the flour on which its bread-making properties largely
depend. The important thing, however, is not entirely the quantity of
gluten, but more particularly its character. Two flours containing the
same amounts of carbohydrates and proteid compounds, when converted into
bread by exactly the same process, may produce bread of entirely
different physical characteristics because of differences in the nature
of the gluten of the two samples. Gluten is composed of two bodies
called gliadin and glutenin. The gliadin, a sort of plant gelatin, is
the material which binds the flour particles together to form the dough,
thus giving it tenacity and adhesiveness; and the glutenin is the
material to which the gliadin adheres. If there is an excess of gliadin,
the dough is soft and sticky, while if there is a deficiency, it lacks
expansive power. Many flours containing a large amount of gluten and
total proteid material and possessing a high nutritive value, do not
yield bread of the best quality, because of an imperfect blending of the
gliadin and glutenin. This question is of much importance in the milling
of wheats, especially in the blending of the different types of wheat.
An abnormally large amount of gluten does not yield a correspondingly
large loaf.
[Illustration: FIG. 49.--BREAD FROM NORMAL FLOUR (1);
GLIADIN EXTRACTED FLOUR (2); AND FROM FLOUR AFTER EXTRACTION OF SUGAR
AND SOLUBLE PROTEIDS (3).]
Experiments were made at the Minnesota Experiment Station to determine
the relation between the nature of the gluten and the character of the
bread. This was done by comparing bread from normal flour with that
from other flour of the same lot, but having part or all of its gliadin
extracted.[64] Dough made from the latter was not sticky, but felt like
putty, and broke in the same way. The yeast caused the mass to expand a
little when first placed in the oven; then the loaf broke apart at the
top and decreased in size. When baked it was less than half the size of
that from the same weight of normal flour, and decidedly inferior in
other respects. The removal of part of the gliadin produced nearly the
same effect as the extraction of the whole of it, and even when an equal
quantity of normal flour was mixed with that from which part of the
gliadin had been extracted, the bread was only slightly improved. In
flour of the highest bread-making properties the two constituents,
gliadin and glutenin, are present in such proportions as to form a
well-balanced gluten.
The proteids of wheat flour are mainly in an insoluble form, although
there are small amounts of albumins and globulins; these are coagulated
by the action of heat during the bread-making process, and rendered
insoluble. A portion of the acid that is developed unites with the
gliadin and glutenin, forming acid proteids, which change the physical
properties of the dough. Both gliadin and glutenin take important parts
in bread making. The removal of gliadin from flour causes complete loss
of bread-making properties. Ordinarily from 45 to 65 per cent of the
total nitrogen of the flour is present in alcohol soluble or gliadin
form. Proteids also undergo hydration during mixing, some water being
chemically united with them, changing their physical properties. This
hydration change is necessary for the full development of the physical
properties of the gluten. The water and salt soluble proteids appear to
take no important part in the bread-making process, as their removal in
no way affects the size of the loaf or general character of the bread.
Because of the action of the acids upon the gliadin, bread contains a
larger amount of alcohol soluble nitrogen or gliadin than the flour from
which the bread was made. It is believed that this action changes the
molecular structure of the protein so that it is more readily separated
into its component parts when it undergoes digestion and assimilation.
182. Production of Volatile Nitrogenous Compounds.--When fermentation
is unnecessarily prolonged, an appreciable amount of nitrogen is
volatilized in the form of ammonia and allied bodies, as amids. During
the process of bread making, the yeast appears to act upon the protein,
as well as upon the carbohydrates, and, as previously stated, losses of
dry matter fall alike upon these two classes of compounds, nitrogenous
and non-nitrogenous. Analyses of the flours and materials used in bread
making, and of the bread, show that ordinarily about 1.5 per cent of the
total nitrogen is liberated in the form of gas during the bread-making
process, and analyses of the gases dispelled in baking show
approximately the same per cent of nitrogen. When bread is dried, as in
a drying oven, a small amount of volatile nitrogen appears to be given
off,--probably as ammonium compounds formed during fermentation. The
nitrogen lost in bread making under ordinary conditions is not
sufficient to affect the nutritive value of the product. The losses of
both nitrogen and carbon are more than offset by the increased
solubility of the proteids and carbohydrates, the preliminary changes
they have undergone making them more digestible and valuable for food
purposes. The nitrogen volatilized in bread making appears to be mainly
that present in the flour in amid forms or liberated as the result of
fermentation processes. The more stable proteids undergo only limited
changes in solubility and are not volatilized.
183. Oxidation of Fat.--Flour contains about 1.25 per cent of fat
mechanically mixed with a small amount of yellow coloring matter. During
the process of bread making the fat undergoes slight oxidation,
accompanied by changes in both physical and chemical properties. The fat
from bread, when no lard or shortening has been added, is darker in
color, more viscous, less soluble in ether, and has a lower iodine
number, than fat from flour. The change in solubility of the fat is not,
however, such as to affect food value, because the fat is not
volatilized, and is only changed by the addition of a small amount of
oxygen from the air. When wheat fat and other vegetable and animal fats
are exposed to the air, they undergo changes known as aging, similar to
the slight oxidation changes in bread making.[64]
184. Influence of the Addition of Wheat Starch and Gluten to
Flour.--Ten per cent or more of starch may be added to normal flour
containing a well-balanced gluten, without decreasing the size of the
loaf. When moist gluten was added to flour, thus increasing the total
amount of gluten, the size of the loaf was not increased[67].
INFLUENCE OF ADDITION OF STARCH AND GLUTEN TO FLOUR
=====================================================================
| SIZE OF LOAF | WEIGHT
---------------------------------------------------------------------
Wheat flour, 14 ounces | 22-1/2 × 17-1/2 | 18.75
Wheat flour, 10% wheat starch | 23-1/2 × 17 | 18.25
Wheat flour, 12.2% wheat starch | 21-1/2 × 17 | 18.00
| |
Wheat flour, 210 grams, about 8 ounces | 12-3/4 × 9 | 12.00
Wheat flour, 10% gluten added, 210 grams | 12-1/2 × 9 | 12.75
Wheat flour, 20% gluten added | 12 × 8-3/4 | 13.00
=====================================================================
So long as the quality of the gluten is not destroyed, the addition of a
small amount of either starch or gluten to flour does not affect the
size of the loaf, but removal of the gluten affects the moisture content
and physical properties of the bread. The addition of starch to flour
has the same effect upon the bread as the use of low gluten
flour,--lessening the capacity of the flour to absorb water and
producing a dryer bread of poorer quality.
185. Composition of Bread.--The composition of bread depends primarily
upon that of the flour from which it was made. If milk and butter (or
lard) are used in making the dough, as is commonly the case, their
nutrients are, of course, added to those of the flour; but when only
water and flour are used, the nutrients of the bread are simply those
of the flour. In either case the amount of nutrients in the bread is
smaller than in the same weight of flour, because a considerable part of
the water or milk used in making the dough is present in the bread after
baking; that is, a pound of bread contains less of any of the nutrients
than a pound of the flour from which the bread was made, because the
proportion of water in the bread is greater. The following table shows
how the composition of flour compares with that of bread, the different
kinds of bread all having been made from the flour with which they are
compared:
COMPOSITION OF FLOUR, AND BREAD MADE FROM IT IN DIFFERENT WAYS
=====================================================================
MATERIAL | WATER | PROTEIN | FAT| C.H.| ASH
---------------------------------------------------------------------
| % | % | % | % | %
Flour | 10.11 | 12.47 |0.86|76.09 |0.47
Bread from flour and water | 36.12 | 9.46 |0.40|53.70 |0.32
Bread from flour, water, and lard | 37.70 | 9.27 |1.02|51.70 |0.31
Bread from flour and skim milk | 36.02 | 10.57 |0.48|52.63 |0.30
=====================================================================
Thus it may be seen that the proportion of water is larger and of each
nutrient smaller in bread than in flour, and that the nutrients of the
flour are increased by those in the materials added in making the bread.
It is apparent that two breads of the same lot of flour may differ,
according to the method used in making, and also that two loaves of
bread made by exactly the same process but from different lots of flour,
even when of the same grade or brand, do not necessarily have the same
composition, because of possible variation in the flours. In bread made
from flour of low gluten content, the per cent of protein is
correspondingly low.
186. Use of Skim Milk and Lard in Bread Making.--When flours low in
gluten are used, skim milk may be employed advantageously in making the
bread, to increase the protein content. Tests show that such bread
contains about 1 per cent more protein than that made with water.
Ordinarily there is no gain from a nutritive point of view in adding an
excessive amount of lard or other shortening, as it tends to widen the
nutritive ratio.
187. Influence of Warm and Cold Flours on Bread Making.--When flour is
stored in a cold closet or storeroom, it is not in condition to produce
a good quality of bread until it has been warmed to a temperature of
about 70° F. Cold flour checks the fermentation process, and is
occasionally the cause of poor bread. On the other hand, when flour is
too warm (98° F.) the influence upon fermentation is unfavorable.
Heating of flour does not affect the bread-making value, provided the
flour is not heated above 158° F. and is subsequently cooled to a
temperature of 70° F. Wheat flour contains naturally a number of
ferment substances, some of which are destroyed by the action of heat.
The natural ferments, or enzymes, of flour appear to take a part in
bread making, imparting characteristic odors and flavors to the product.
[Illustration: FIG. 50.-BREAD FROM (1) GRAHAM, (2) ENTIRE
WHEAT, AND (3) WHITE FLOUR.
The same amounts of flour were used in making all of the breads.]
188. Variations in the Process of Bread Making.--Since flours differ
so in chemical composition, and the yeast plant acts upon all the
compounds of flour, it naturally follows that bread making is not a
simple but a complex operation, resulting in a number of intricate
chemical reactions, which it is necessary to control and many of which
are only imperfectly understood. Bread of the best physical quality and
commercial value is made of flour from fully matured, hard wheats,
containing a low per cent of acid, no foreign ferment materials or their
products, and at least 12-1/2 per cent of proteids, of which the larger
portion is in the form of gliadin. It is believed that a better quality
of bread could be produced from many flours by slight changes or
modifications in the process of bread making. It cannot be expected that
the same process will give the best results alike with all types and
kinds of flour. The kind of fermentation process that will produce the
best bread from a given type of flour can be determined only by
experimentation. Poor bread making is due as often to lack of skill on
the part of the bread maker, and to poor yeast, as it is to poor quality
of flour. Frequently the flour is blamed when the poor bread is due to
other factors. Lack of control of the fermentation process, and the
consequent development of acid and other organisms which check the
activity of the alcoholic ferments, is a frequent cause of poor bread.
189. Digestibility of Bread.--Extensive experiments have been made by
the Office of Experiment Stations of the United States Department of
Agriculture, at the Minnesota and Maine Experiment Stations, to
determine the digestibility and nutritive value of bread. Different
kinds and types of wheat were milled so as to secure from each three
flours: graham, entire wheat, and standard patent. The flours were made
into bread, and the bread fed to workingmen, and its digestibility
determined. The experiments taken as a whole show that bread is an
exceedingly digestible food, nearly 98 per cent of the starch or
carbohydrate nutrients and about 88 per cent of the gluten or proteid
constituents being assimilated by the body. In the case of the graham
and entire wheat flours, although they contained a larger total amount
of protein, the nutrients were not as completely digested and absorbed
by the body as were those of the white flour. The body secured a larger
amount of nutrients from the white than from the other grades of flour,
the digestibility of the three types being as follows: standard patent
flour, protein 88.6 per cent and carbohydrates 97.7 per cent; entire
wheat flour, protein 82 percent and carbohydrates 93.5 per cent; graham
flour, protein 74.9 per cent and carbohydrates 89.2 per cent. The low
digestibility of the protein of the graham and entire wheat flours is
supposed to be due to the coarser granulation; the proteins, being
embedded and surrounded with cellular tissue, escape the action of the
digestive fluids. Microscopic examination of the feces showed that often
entire starch grains were still inclosed in the woody coverings and
consequently had failed to undergo digestion.[62], [64], [67], [86]
190. Use of Graham and Entire Wheat in the Dietary.--Entire wheat and
graham flours should be included in the dietary of some persons, as they
are often valuable because of their physiological action, the branny
particles stimulating the process of digestion and encouraging
peristaltic action. In the diet of the overfed, they are valuable for
the smaller rather than the larger amount of nutrients they contain.
Also they supply bulk and give the digestive tract needed exercise. For
the laboring man, where it is necessary to obtain the largest amount of
available nutrients, bread from white flour should be supplied; in the
dietary of the sedentary, graham and entire wheat flours can, if found
beneficial, be made to form an essential part. The kind of bread that it
is best to use is largely a matter of personal choice founded upon
experience.
"When we pass on to consider the relative nutritive values of white
and whole-meal bread, we are on ground that has been the scene of
many a controversy. It is often contended that whole-meal is
preferable to white bread, because it is richer in proteid and
mineral matter, and so makes a better balanced diet. But our
examination of the chemical composition of whole-meal bread has
shown that as regards proteid at least, this is not always true,
and even were it the case, the lesser absorption of whole-meal
bread, which we have seen to occur, would tend to annul the
advantage.... On the whole, we may fairly regard the vexed question
of whole-meal _versus_ white bread as finally settled and settled
in favor of the latter."[28]
"The higher percentage of nitrogen in bran than in fine flour has
frequently led to the recommendation of the coarser breads as more
nutritious than the finer. We have already seen that the more
branny portions of the grain also contain a much larger percentage
of mineral matter. And, further, it is in the bran that the largest
proportion of fatty matter--the non-nitrogenous substance of higher
respiratory capacity which the wheat contains--is found. It is,
however, we think, very questionable whether upon such data alone
a valid opinion can be formed of the comparative values of bread
made from the finer or courser flours ground from one and the same
grain. Again, it is an indisputable fact that branny particles when
admitted into the flour in the degree of imperfect division in
which our ordinary milling processes leave them very considerably
increase the peristaltic action, and hence the alimentary canal is
cleared much more rapidly of its contents. It is also well known
that the poorer classes almost invariably prefer the whiter bread,
and among some of those who work the hardest and who consequently
soonest appreciate a difference in nutritive quality (navvies, for
example) it is distinctly stated that their preference for the
whiter bread is founded on the fact that the browner passes through
them too rapidly; consequently, before their systems have extracted
from it as much nutritious matter as it ought to yield them.... In
fact, all experience tends to show that the state as well as the
chemical composition of our food must be considered; in other
words, that the digestibility and aptitude for assimilation are not
less important qualities than its ultimate composition.
"But to suppose that whole-wheat meal as ordinarily prepared is, as
has generally been assumed, weight for weight more nutritious than
ordinary bread flour is an utter fallacy founded on theoretical
text-book dicta, not only entirely unsupported by experience, but
inconsistent with it. In fact, it is just the poorer fed and the
harder working that should have the ordinary flour bread rather
than the whole-meal bread as hitherto prepared, and it is the
overfed and the sedentary that should have such whole-meal bread.
Lastly, if the whole grain were finely ground, it is by no means
certain that the percentage of really nutritive nitrogenous matters
would be higher than in ordinary bread flour, and it is quite a
question whether the excess of earthy phosphates would not then be
injurious."--LAWES AND GILBERT.[68]
* * * * *
"According to the chemical analysis of graham, entire wheat, and
standard patent flours milled from the same lot of hard Scotch Fife
spring wheat, the graham flour contained the highest and the
patent flour the lowest percentage of total protein. But according
to the results of digestion experiments with these flours the
proportions of digestible or available protein and available energy
in the patent flour were larger than in either the entire wheat or
the graham flour. The lower digestibility of the protein of the
latter is due to the fact that in both these flours a considerable
portion of this constituent is contained in the coarser particles
(bran), and so resists the action of the digestive juices and
escapes digestion. Thus while there actually may be more protein in
a given amount of graham or entire wheat flour than in the same
weight of patent flour from the same wheat, the body obtains less
of the protein and energy from the coarse flour than it does from
the fine, because, although the including of the bran and germ
increases the percentage of protein, it decreases its
digestibility. By digestibility is meant the difference between the
amounts of the several nutrients consumed and the amount excreted
in the feces.
"The digestibility of first and second patent flours was not
appreciably different from that of standard patent flour. The
degree of digestibility of all these flours is high, due largely to
their mechanical condition; that is, to the fact that they are
finely ground."--SNYDER.[62]
For a more extended discussion of the subject, the student is referred
to Bulletins 67, 101, and 126, Office of Experiment Stations, United
States Department of Agriculture.
191. Mineral Content of White Bread.--Average flour contains from 0.4
to 0.5 of 1 per cent of ash or mineral matter, the larger portion being
lime and magnesia and phosphate of potassium. It is argued by some that
graham and entire wheat flours should be used liberally because of their
larger mineral content and their greater richness in phosphates. In a
mixed dietary, however, in which bread forms an essential part, there is
always an excess of phosphates, and there is nothing to be gained by
increasing the amount, as it only requires additional work of the
kidneys for its removal. Few experiments have been made to determine the
phosphorus requirements of the human body, but these indicate that it is
unnecessary to increase the phosphate content of a mixed diet. It is
estimated that less than two grams per day of phosphates are required to
meet all of the needs of the body, and in an average mixed ration there
are present from three to five grams and more. A large portion of the
phosphate compounds of white bread is present in organic combinations,
as lecithin and nucleated proteids, which are the most available forms,
and more valuable for purposes of nutrition than the mineral phosphates.
In the case of graham and entire wheat flours, a proportionally smaller
amount of the phosphates are digested and assimilated than from the
finer grades of flour.
192. Comparative Digestibility of New and Old Bread.--With healthy
persons there is no difference whatever in the completeness of
digestibility of old and new bread; one appears to be as thoroughly
absorbed as the other. In the case of some individuals with impaired
digestion there may be a difference in the ease and comfort with which
the two kinds of bread are digested, but this is due mainly to
individuality and does not apply generally. The change which bread
undergoes when it is kept for several days is largely a loss of moisture
and development of a small amount of acid and other substances from the
continued ferment action.
193. Different Kinds of Bread.--According to variations in method of
preparation, there are different types and varieties of bread, as the
"flat bread" of Scandinavian countries, unleavened bread, Vienna bread,
salt rising bread, etc. Bread made with baking powder differs in no
essential way from that made with yeast, except in the presence of the
residue from the baking powder, discussed in Chapter XII. Biscuits,
wheat cakes, crackers, and other food materials made principally from
flour, have practically the same food value as bread. It makes but
little difference in what way flour is prepared as food, for in its
various forms it has practically the same digestibility and nutritive
value.
194. Toast.--When bread is toasted there is no change in the
percentage of total nutrients on a dry matter basis. The change is in
solubility and form, and not in amount of nutrients available. Some of
the starch becomes dextrine, which is more soluble and digestible.[5]
Proteids, on the other hand, are rendered less soluble, which appears to
slightly lower the digestion coefficient. They are somewhat more readily
but not quite so completely digested as those of bread. Digestion
experiments show that toast more readily yields to the diastase and
other ferments than does wheat bread. Toasting brings about ease of
digestion rather than increased completeness of the process. Toast is a
sterile food, while bread often contains various ferments which have not
been destroyed by baking. These undergo incubation during the process of
digestion, particularly in the case of individuals with diseases of the
digestive tract. With normal digestion, however, these ferment bodies do
not develop to any appreciable extent, as the digestive tract disinfects
itself. When the flour is prepared from well cleaned wheat and the
ferment substances which are present mainly in the bran particles have
been removed, a flour of higher sanitary value is secured.
CHAPTER XII
BAKING POWDERS
195. General Composition.--All baking powders contain at least two
materials; one of these has combined carbon dioxid in its composition,
the other some acid constituent which serves to liberate the gas. The
material from which the gas is obtained is almost invariably sodium
bicarbonate, NaHCO_{3}, commonly known as "soda" or "saleratus."
Ammonium carbonate has been used to some extent, but is very seldom used
at the present time. The acid constituent may be one of several
materials, the most common being cream of tartar, tartaric acid, calcium
phosphate, or alum. These may be used separately or in combination. The
various baking powders are designated according to the acid constituent,
as "cream of tartar," "phosphate," and "alum" powders. All of them
liberate carbon dioxid gas, but the products left in the food differ
widely in nature and amount[69].
Baking powder is a chemical preparation which, when brought in contact
with water, liberates carbon dioxid gas. The baking powder is mixed dry
with flour, and when this is moistened the carbon dioxid that is
liberated expands the dough. The action is similar to that of yeast
except that in the case of yeast the gas is given off much more slowly
and no residue is left in the bread. When baking powder is used, there
is a residue left in the food which varies with the material in the
powder. It is the nature and amount of this residue that is important
and makes one baking powder more desirable than another.
[Illustration: FIG. 51.--INGREDIENTS OF A BAKING POWDER.
1, baking powder; 2, cream of tartar; 3, baking soda; 4, starch.]
196. Cream of Tartar Powders.--The acid ingredient of the cream of
tartar powders is tartaric acid, H_{2}C_{4}H_{4}O_{6}. Cream of tartar
is potassium acid tartrate, KHC_{4}H_{4}O_{6}; it contains one atom of
replaceable hydrogen, which imparts the acid properties, and it is
prepared from crude argol, a deposit of grape juice when wine is made.
The residue from this powder is sodium potassium tartrate,
NaKC_{4}H_{4}O_{6}, commonly known as Rochelle salt. This is the active
ingredient of Seidlitz powders and has a purgative effect when taken
into the body. The dose as a purgative is from one half to one ounce. A
loaf of bread as ordinarily made with cream of tartar powder contains
about 160 grains of Rochelle salt, which is 45 grains more than is found
in a Seidlitz powder, but the amount actually eaten at any one time is
small and its physiological effect can probably be disregarded. When a
cream of tartar baking powder is used, the reaction takes place
according to the following equation:
188 84 210 44 18
HKH_{4}C_{4}O_{6} + NaHCO_{3} = KNaC_{4}H_{4}O_{6} + CO_{2} + H_{2}O.
The crystallized Rochelle salt contains four molecules of water, so
that, even allowing for some starch filler, there is very nearly as much
weight of material (Rochelle salt) left in the food as there was of the
original powder. If free tartaric acid were used instead of potassium
acid tartrate, the reaction would be as follows:
150 168 230 88
H_{2}C_{4}H_{4}O{6} + 2NaHCO_{3} = Na_{2}C_{2}H_{4}O_{6}.2 H_{2}O + 2CO_{2}.
But the residue, sodium tartrate, is less in proportion. It has
physiological properties very similar to Rochelle salt. Tartaric acid is
seldom used alone, but very often in combination with cream of tartar.
It is more expensive than cream of tartar; but not so much is required,
and it is more rapid in action.
197. Phosphate Baking Powders.--Here the acid ingredient is phosphoric
acid and the compound usually employed is mono-calcium phosphate,
CaH_{4}(PO-{4})_{2}. This is made by the action of sulphuric acid on
ground bone (Ca_{3}(PO_{4})_{2} + 2 H_{2}SO_{4} = CaH_{4}(PO_{4})_{2} +
2 CaSO_{4}), and it is difficult to free it from the calcium phosphate
formed at the same time; hence such powders contain more or less of this
inert material. The reaction which occurs with a phosphate powder is as
follows:
234 168 136
CaH_{4}(PO_{4})_{2} + 2 NaHCO_{3} = CaHPO_{4}
88 36 142
+ 2 CO_{2} + 2 H_{2}O + Na_{2}HPO_{4}.
Sodium phosphate, according to the United States Dispensatory, is
"mildly purgative in doses of from 1 to 2 ounces." The claim is made by
the makers of phosphate baking powders that the phosphates of sodium and
calcium, products left after the baking, restore the phosphates which
have been lost from the flour in the bran. This baking powder residue
does not restore the phosphates in the same form in which they are
present in grains and it does furnish them in larger amounts--nearly
tenfold. However, the residue from these powders is probably less
objectionable than that from alum powders. The chief drawback to the
phosphate powders is their poor keeping qualities.
198. Alum Baking Powders.--Sulphuric acid is the acid constituent of
these powders. The alums are double sulphates of aluminium and an
alkali metal, and have the general formula _x_Al(SO_{4})_{2} in which
_x_ may be K, Na, or NH_{4}, producing respectively a potash, soda, or
ammonia alum. Potash alum is most commonly used, soda and ammonia alums
to a less extent. The reaction takes place as follows:
475 504 157
2 NH_{4}Al(SO_{4})_{2} + 6 NaHCO_{3} = Al_{2}(OH)_{6}
426 132 264
+ 3 Na_{2}SO_{4} + (NH_{4})_{2}SO_{4} + 6 CO_{2}.
If it is a potash or soda alum, simply substitute K or Na for NH_{4}
throughout the equation. The best authorities regard alum baking powders
as the most objectionable. Ammonia alum is without doubt the worst form,
since all of the ammonium compounds have an extremely irritating effect
on animal tissue. Sulphates of sodium and potassium are also
objectionable. Aluminium hydroxide is soluble in the slightly acid
gastric juice and has an astringent action on animal tissue, hindering
digestion in a way similar to the alum itself. Many of the alum powders
contain also mono-calcium phosphate; the reaction is as follows:
475 234 336
2 NH_{4}Al(SO_{4})_{2} + CaH_{4}(PO_{4})_{2} + 4 NaHCO_{3}
245 136 132
= Al_{2}(PO_{4})_{2} + CaSO_{4} + (NH_{4})_{2}SO_{4}
284 176 72
+ 2 Na_{2}SO_{4} + 4 CO_{2} + 4 H_{2}O.
These are probably less injurious than the straight alum powders,
although the residues are, in general, open to the same objection.
199. Inspection of Baking Powders.--Many of the states have enacted
laws seeking to regulate the sale of alum baking powders. Some of these
laws simply require the packages to bear a label setting forth the fact
that alum is one of the ingredients; others require the baking powder
packages to bear a label naming all the ingredients of the powder.
200. Fillers.--All baking powders contain a filler of starch. This is
necessary to keep the materials from acting before the powder is used.
The amount of filler varies from 15 to 50 per cent; the least is found
in the tartrate powders and the most in the phosphate powders. The
amount of gas which a powder gives off regulates its value; it should
give off at least 1/8 of its weight.
201. Home-made Baking Powders.--Baking powders can be made at home for
about one half what they usually cost and they will give equal
satisfaction. The following will make a long-keeping powder: cream of
tartar, 8 ounces; baking soda, 4 ounces; corn starch, 3 ounces. For a
quick-acting powder use but one ounce of starch. The materials should be
thoroughly dry. Mix the soda and starch first by shaking well in a glass
or tin can. Add the cream of tartar last and shake again. Thorough
mixing is essential to good results. Cream of tartar is often
adulterated, but it can be obtained pure from a reliable druggist. To
insure baking powders remaining perfectly dry, they should always be
kept in glass or tin cans, never in paper.
CHAPTER XIII
VINEGAR, SPICES, AND CONDIMENTS
202. Vinegar.--Vinegar is a dilute solution of acetic acid produced by
fermentation, and contains, in addition to acetic acid, small amounts of
other materials in solution, as mineral matter and malic acid, according
to the material from which the vinegar was made. Unless otherwise
designated, vinegar in this country is generally considered to be made
from apples. Other substances, however, are used, as vinegar can be
manufactured from a variety of fermentable materials, as molasses,
glucose, malt, wine, and alcoholic beverages in general. The chemical
changes which take place in the production of vinegars are: (1)
inversion of the sugar, (2) conversion of the invert sugars into
alcohol, and (3) change of alcohol into acetic acid. All these chemical
changes are the result of ferment action. The various invert ferments
change the sugar into dextrose and glucose sugars; then the alcoholic
ferment produces alcohol and carbon dioxid from the invert sugars, and
finally the acetic acid ferment completes the work by converting the
alcohol into acetic acid. The chemical changes which take place in these
different steps are:
sucrose dextrose levulose
(1) C_{12}H_{22}O_{11} + H_{2}O = C_{6}H_{12}O_{6} + C_{6}H_{12}O_{6};
dextrose alcohol
(2) C_{6}H_{12}O_{6} = 2 C_{2}H_{5}OH + 2 CO_{2};
alcohol acid
(3) C_{2}H_{5}OH + 2 O = HC_{2}H_{3}O_{2} + H_{2}O.
[Illustration: FIG. 52.--ACETIC ACID FERMENTS. (After KÖNIG.)]
The acetic acid organism, _Mycoderma aceti_, can work only in the
presence of oxygen. It is one of the aerobic ferments, and is present in
what is known as the "mother" of vinegar and is secreted by it. When
vinegar is made in quantity, the process is hastened by allowing the
alcoholic solution to pass through a narrow tank rilled with shavings
containing some of the ferment material, and at the same time air is
admitted so as to secure a good supply of oxygen. When vinegar is made
by allowing cider or wine to stand in a warm place until the
fermentation process is completed, a long time is required--the length
of time depending upon the supply of air and other conditions affecting
fermentation.
In some countries malt vinegar is common. This is produced by allowing a
wort made from malt and barley to undergo acetic acid fermentation,
without first distilling the alcohol as is done in the preparation of
spirit vinegar. In various European countries wine vinegar is in general
use and is made by acetification of the juice of grapes. Sometimes
spirit vinegar is made from corn or barley malt. Alcoholic fermentation
takes place, the alcohol is distilled so that a weak solution remains,
which is acetified in the ordinary way. Such a vinegar can be produced
very cheaply and is much inferior in flavor to genuine wine or cider
vinegar.
Vinegar, when properly made, should remain clear, and should not form a
heavy deposit or produce any large amount of the fungous growth,
commonly called the "mother" of vinegar. In order to prevent the vinegar
from becoming cloudy and forming deposits, it should be strained and
stored in clean jugs and protected from the air. So long as air is
excluded further acetic acid fermentation and production of "mother" of
vinegar cannot take place. When the vinegar is properly made and the
fermentation process has been completed, the acid already produced
prevents all further development of acetic acid ferments. When vinegar
becomes cloudy and produces deposits, it is an indication that the
acetic fermentation has not been completed.
The national standard for pure apple cider vinegar calls for not less
than 4 grams acetic acid, 1.6 grams of apple solids, and 0.25 grams of
apple ash per 100 cubic centimeters, along with other characteristics,
as acidity, sugar, and phosphoric acid content. Many states have special
laws regarding the sale of vinegar.
203. Adulteration of Vinegar.--Vinegar is frequently adulterated by
the addition of water, or by coloring spirit vinegar, thus causing it to
resemble cider vinegar. Formerly vinegar was occasionally adulterated by
the use of mineral acids, as hydrochloric or sulphuric, but since acetic
acid can be produced so cheaply, this form of adulteration has almost
entirely disappeared. Colored spirit vinegar contains merely a trace of
solid matter and can be readily distinguished from cider vinegar by
evaporating a small weighed quantity to dryness and determining the
weight of the solids. Occasionally, however, glucose and other materials
are added so as to give some solids to the spirit vinegar, but such a
vinegar contains only a trace of ash[18]. Attempts have also been made
to carry the adulteration still further by adding lime and soda to give
the colored spirit vinegar the necessary amount of ash. Malt, white
wine, glucose, and molasses vinegars when properly manufactured and
unadulterated are not objectionable, but too frequently they are made to
resemble and sell as cider vinegar. This is a fraud which affects the
pocketbook rather than the health. For home use apple cider vinegar is
highly desirable. There is no food material or food adjunct, unless
possibly ground coffee and spices, so extensively adulterated as
vinegar.
Vinegar has no food value whatever, and is valuable only for giving
flavor and palatability to other foods, and to some extent for the
preservation of foods. It is useful in the household in other ways, as
it furnishes a dilute acid solution of aid in some cooking and baking
operations for liberating gas from soda, and also when a dilute acid
solution is required for various cleaning purposes.
Vinegar should never be kept in tin pails, or any metallic vessel,
because the acetic acid readily dissolves copper, tin, iron, and the
ordinary metals, producing poisonous solutions. Earthenware jugs,
porcelain dishes, glassware, or wooden casks are all serviceable for
storing vinegar.
204. Characteristics of Spices.[70]--Spices are aromatic vegetable
substances characterized as a class by containing some essential or
volatile oil which gives taste and individuality to the material. They
are used for the flavoring of food and are composed of mineral matter
and the various nitrogenous and non-nitrogenous compounds found in all
plant bodies. Since only a comparatively small amount of a spice is used
for flavoring purposes, no appreciable nutrients are added to the food.
Some of the spices have characteristic medicinal properties.
Occasionally they are used to such an extent as to mask the natural
flavors of foods, and to conceal poor cooking and preparation or poor
quality. For the microscopic study of spices the student is referred to
Winton, "Microscopy of Vegetable Foods," and Leach, "Food Inspection and
Analysis."
205. Pepper.--Black and white pepper are the fruit of the pepper plant
(_Piper nigrum_), a climbing perennial shrub which grows in the East and
West Indies, the greatest production being in Sumatra. For the black
pepper, the berry is picked before thoroughly ripe; for the white
pepper, it is allowed to mature. White pepper has the black pericarp or
hull removed. Pepper owes its properties to an alkaloid, piperine, and
to a volatile oil. In the black pepper berries there is present ash to
the extent of about 4.5 per cent, it ought not to be above 6.5 per cent;
ether extract, including piperine and resin, not less than 6.5 per cent;
crude fiber not more than 16 per cent; also some starch and nitrogenous
material. The white pepper contains less ash and cellulose than the
black pepper. Ground pepper is frequently grossly adulterated; common
adulterants being: cracker crumbs, roasted nut shells and fruit stones,
charcoal, corn meal, pepper hulls, mustard hulls, and buckwheat
middlings. The pepper berries wrinkle in drying, and this makes it
difficult to remove the sand which may have adhered to them. An
excessive amount of sand in the ash should be classed as adulteration.
Adulterants in pepper are detected mainly by the use of the microscope.
The United States standard for pepper is: not more than 7 per cent total
ash, 15 per cent fiber, and not less than 25 per cent starch and 6 per
cent non-volatile ether extract.[71]
206. Cayenne.--Cayenne or red pepper is the fruit pod of a plant,
_capsicum_, of which there are several varieties,--the small-fruited
kind, used to make cayenne or red pepper; and the tabasco sort, forming
the basis of tabasco sauce. It is grown mainly in the tropics, and was
used there as a condiment before the landing of Columbus, who took
specimens back to Europe. Cayenne pepper contains 25 per cent of oil,
about 7 per cent of ash, and a liberal amount of starch. The adulterants
are usually of a starchy nature, as rice or corn meal, and the product
is often colored with some red dye.
207. Mustard.--Mustard is the seed of the mustard plant, and is most
often found in commerce in the ground form. The black or brown mustard
has a very small seed and the most aroma. White mustard is much larger
and is frequently used unground. For the ground mustard, only the
interior of the seed is used, the husk being removed in the bolting.
Mustard contains a large amount of oil, part of which is usually
expressed before grinding, and this is the form in which spice grinders
buy it. In mustard flour there is: ash from 4 to 6 per cent, volatile
oil from 0.5 to 2 per cent, fixed oil from 15 to 25 per cent, crude
fiber from 2 to 5 per cent, albuminoids from 35 to 45 per cent, and a
little starch. The principal adulterants are wheat, corn, and rice
flour. When these are used, the product is frequently colored with
turmeric, a harmless vegetable coloring material.
208. Ginger.--Ginger is the rhizome or root of a reed-like plant
(_Zingiber officinale_), native in tropical Asia, chiefly India. It is
cultivated in nearly all tropical countries. When unground it usually
occurs in two forms: dried with the epidermis, or with the epidermis
removed, when it is called scraped ginger. Very frequently a coating of
chalk is given, as a protection against the drug store beetle. Jamaica
ginger is the best and most expensive. Cochin, scraped, African, and
Calcutta ginger range in price in the order given. Ginger contains from
3.6 to 7.5 per cent of ash, from 1.5 to 3 per cent of volatile oil, and
from 3 to 5.5 per cent of fixed oil. There is a large amount of starch.
The chief adulterants are rice, wheat, and potato starch, mustard hulls,
exhausted ginger from ginger-ale and extract factories, sawdust and
ground peanut-shells, and turmeric is frequently used for coloring the
product. The United States standard for ginger is not more than 42 per
cent starch, 8 per cent fiber, and 6 per cent total ash.[71]
209. Cinnamon and Cassia.--The bark of several species of plants
growing in tropical countries furnishes these spices. True cinnamon is a
native of Ceylon, while the cassias are from Bengal and China. In this
country there is more cassia used than cinnamon--cinnamon being rarely
found except in drug stores. Cassia bark is much thicker than cinnamon
bark. The ground spice contains about 1.5 per cent volatile oil and the
same amount of fixed oil, 4 per cent of ash, and some fiber, nitrogenous
matter, and starch. Cereals, cedar sawdust, ground nutshells, oil meal,
and cracker crumbs are the chief adulterants.
210. Cloves.--Cloves are the flower buds of an evergreen tree that
grows in the tropics. These are picked by hand and dried in the sun. In
the order of value, Penang, Sumatra, Amboyna, and Zanzibar furnish the
chief varieties. Cloves rarely contain more than 8 per cent ash, or less
than 10 per cent volatile oil and 4 per cent fixed oil, and 16 to 20 per
cent of tannin-yielding bodies. No starch is present. The chief
adulterants of ground cloves are spent cloves, allspice, and ground
nutshells. Clove stems are also sometimes used and may be detected by a
microscopical examination, since they contain many thick-walled cells
and much fibrous tissue.
211. Allspice.--Allspice, or pimento, is the fruit of an evergreen
tree common in the West Indies. It is a small, dry, globular berry,
two-celled, each cell having a single seed. Allspice contains about 2.5
per cent volatile oil, 4 per cent fixed oil, and 4.5 per cent ash.
Because of its cheapness, it is not generally adulterated, cereal
starches being the most common adulterants.
212. Nutmeg.--Nutmeg is the interior kernel of the fruit of a tree
growing in the East Indies. The fruit resembles a small pear. A fleshy
mantle of crimson color, which is mace, envelopes the seed. Nutmeg
contains about 2.2 per cent ash, 2.5 to 5 per cent volatile oil, and 25
to 35 per cent fixed oil. Mace has practically the same composition.
Extensive adulteration is seldom practiced. The white coating on the
surface of the nutmeg is lime, used to prevent sprouting of the germ.
CHAPTER XIV
TEA, COFFEE, CHOCOLATE, AND COCOA
[Illustration: FIG. 53.--TEA LEAF. (After
WINTON.)]
213. Tea is the prepared leaf of an evergreen shrub or small tree
cultivated chiefly in China and Japan. There are two varieties of
plants. The Assamese, which requires a very moist, hot climate, yields
in India and Ceylon about 400 pounds per acre, and may produce as high
as 1000 pounds. From this plant a number of flushes or pickings are
secured in a year. The Chinese plant grows in cooler climates and has a
smaller, tougher, and darker leaf, which is more delicate than that of
the Assamese and is usually made into green tea. The Chinese tea plant
yields only four or five flushes a year. About 40 per cent of the tea
used in this country comes from Japan and 50 per cent from China. The
tea industry of India and Ceylon has developed rapidly in late years,
and is now second only to that of China. Tea has been raised upon a
small scale in the United States. The quality or grade of the tea
depends upon the leaves used and the method of curing.
214. Composition of Tea.--Black and green teas are produced from the
same species of plant, but owe their difference in color as well as
flavor and odor to methods of preparation. The same plant may yield
several grades of both green and black tea. To produce black tea, the
leaves are bruised to liberate the juices, allowed to ferment a short
time, which develops the color, and then dried.[73] For green tea the
fresh leaves are roasted or steamed, then rolled and dried as quickly as
possible to prevent fermentation. The smaller leaves and the first
picking produce the finest quality of tea. The characteristic flavor and
odor of tea are imparted by a volatile oil, although the odor is
sometimes altered by the tea being brought in contact with orange
flowers, jessamine, or the fragrant olive. There are also present in tea
an alkaloid, theine, which gives the peculiar physiological properties,
and tannin, upon which depends largely the strength of the tea infusion.
The composition of tea is as follows:
===========================================
|ORIGINAL| GREEN | BLACK
| TEA | TEA | TEA
-------------------------------------------
Tannin, per cent | 12.91 | 10.64 | 4.89
Theine, per cent | 3.30 | 3.20 | 3.30
Ash, per cent | 4.97 | 4.92 | 4.93
Fiber, per cent | 10.44 | 10.06 | 10.07
Protein, per cent | 37.33 | 37.43 | 38.90
(all insoluble) | | |
===========================================
It will be noticed that green tea contains twice as much tannin as black
tea; during the fermentation which the black tea undergoes, some of the
tannin is decomposed. There is a large amount of protein in tea, but it
is of no food value, because of its insolubility. About half of the ash
is soluble. The tannin is readily soluble, and for this reason green tea
especially should be infused for a very short time and never boiled.
Tannin in foods in large amounts may interfere with the normal digestion
of the protein compounds, because it coagulates the albumin and peptones
after they have become soluble, and thus makes additional work for the
digestive organs.
215. Judging Teas.--Teas are judged according to: (1) the tea as it
appears prepared for market, (2) the infusion, and (3) the out-turn
after infusion. The color should be uniform; if a black tea, it should
be grayish black, not a dead black. The leaves should be uniform in size
or grade. The quality and grade are dependent upon flavor, and, with the
strength of the infusion, are determined by tasting. This work is
rapidly done by the trained tea taster. The out-turn should be of one
color; no bright green leaves should be present; evenness of make is
judged by the out-turn. The flavor of a tea is largely a matter of
personal judgment, but from a physiological point of view black teas are
given the preference.
216. Adulteration of Tea.--A few years ago tea was quite extensively
adulterated, but the strict regulation of the government regarding
imported tea has greatly lessened adulteration. The most common form
was the use of spent leaves, _i.e._ leaves which had been infused.
Leaves of the willow and other plants which resemble tea were also used,
as well as large quantities of tea stems. Facing or coloring is also an
adulteration, since it is done to give poor or damaged tea a brighter
appearance. "Facing consists in treating leaves damaged in manufacture
or which from age are inferior, with a mixture containing Prussian blue,
turmeric, indigo, or plumbago to impart color or gloss, and with a
fraudulent intent. There is no evidence that the facing agents are
deleterious to health in the small quantities used, but as they are used
for purposes of deception, they should be discouraged."[73] Facing and
the addition of stems are the chief adulterations practiced at present.
217. Food Value and Physiological Properties of Tea.--Tea infusion
does not contain sufficient nutrients to entitle it to be classed as a
food. It is with some persons a stimulant. The caffein or theine in tea
is an alkaloid that has characteristic physiological properties. In
doses of from three to five grains, according to the United States
Dispensatory, "it produces peculiar wakefulness." Larger doses produce
intense physical restlessness, mental anxiety, and obstinate
sleeplessness. "It has no effect upon the motor nerves, but is believed
to have a visible effect upon the sensatory nerves." (United States
Dispensatory.) Experiments with animals show that it causes elevation
of the arterial pressure. It is used as a cardiac stimulant. The
quantity of theine consumed in a cup of tea is about 4/5 of a grain, or
1/4 of a medicinal dose.
[Illustration: FIG. 54.--COFFEE BERRIES.
1, Mocha; 2, Java; 3, Rio.]
218. Composition of Coffee.--The coffee tree is an evergreen
cultivated in the tropics. It grows to a height of 30 feet, but when
cultivated is kept pruned to from 6 to 10 feet. The fruit, which
resembles a small cherry, with two seeds or coffee grains embedded in
the pulp, is dried and the seeds removed, cleaned, and graded. Coffee
has an entirely different composition from tea; it is characterized by
a high per cent of fat and soluble carbohydrates, and also contains an
essential oil and caffein, an alkaloid identical with theine. Tannic
acid, not as free acid, is combined with caffein as a tannate.
======================================
|RAW COFFEE|ROASTED COFFEE
--------------------------------------
| Per Cent | Per Cent
Water | 11.23 | 1.15
Ash | 3.92 | 4.75
Fat | 12.27 | 14.48
Sugar, etc. | 0.66 | 8.55
Protein | 12.07 | 13.98
Caffein | 1.21 | 1.24
======================================
The high per cent of sugar and other soluble carbohydrates in roasted
coffee is caused by the action of heat upon the non-nitrogenous
compounds. Coffee cannot be considered a food, because only a
comparatively small amount of the nutrients are soluble and available.
It is a mildly stimulating beverage. With some individuals it appears to
promote the digestive process, while with others its effect is not
beneficial. Coffee is more extensively used in this country than tea,
and is subject to greater adulteration. It is adulterated by facing and
glazing; _i.e._ coloring the berries to resemble different grades and
coating them with caramel and dextrine. Spent coffee grains and coffee
that has been extracted without grinding are also used as adulterants.
Imitation berries made of rye, corn, or wheat paste, molded, colored
with caramel, and baked have been found mixed with genuine coffee
berries. Roasted cereals and chicory are used extensively to adulterate
ground coffee. Chicory is prepared from the root of the chicory plant,
which belongs to the same family as the dandelion. It is claimed by some
that a small amount of chicory improves the flavor of coffee. However,
when chicory is added to coffee, it should be so stated on the label and
the amount used given. The dextrine and sugar used in glazing are
browned or caramelized during roasting and impart a darker color to the
infusion, making it appear better than it really is. The glazing also
makes the coffee retain moisture which would otherwise be driven off
during roasting. Coffee contains such a large per cent of oil that the
berries generally float when thrown on water, while the imitation
berries sink. Chicory also sinks rapidly and colors the water brown,
while the coffee remains floating for some time.
There are three kinds of coffee in general use: Java, Mocha, and Rio or
Brazil. The Brazil coffee has the largest berry and is usually styled by
dealers as "low" or "low middlings." The Java coffee berries are smaller
and paler in color, the better grades being brown. Mocha usually
commands the highest price in commerce. The seeds are small and dark
yellow before roasting.
219. Cereal Coffee Substitutes.
"A few of these preparations contain a little true coffee, but for
the most part they appear to be made of parched grains of barley,
wheat, etc., or of grain mixed with pea hulls, ground corncobs, or
wheat middlings. It is said that barley or wheat parched, with a
little molasses, in an ordinary oven, makes something
indistinguishable in flavor from some of the cereal coffees on the
market. If no coffee is used in the cereal preparations, the claim
that they are not stimulating is probably true. As for the
nutritive value, parching the cereals undoubtedly renders some of
the carbohydrates soluble, and a part of this soluble matter passes
into the decoction, but the nutritive value of the infusion is
hardly worth considering in the dietary."[56]
220. Cocoa and Chocolate Preparations.--Cocoa and chocolate are
manufactured from the "cocoa bean," the seed of a tree native to
tropical America. The beans are inclosed in a lemon-yellow, fleshy pod.
They are removed from the pulp, allowed to undergo fermentation, and
dried by exposure to the air and light, which hardens them and gives
them a red color. This method produces what is known as the "fermented
cocoa." For the "unfermented cocoa," the beans are dried without
undergoing fermentation. Fermentation removes much of the acidity and
bitterness characteristic to the unfermented bean, and when properly
regulated develops flavor. The original bean contains about 50 per cent
fat, part of which is removed in preparing the cocoa. This fat is sold
as cocoa butter. In the preparation of some brands of cocoa, alkalies,
such as soda and potash, are used to form a combination with the fat to
prevent its separating in oily globules. This treatment improves the
appearance of the cocoa, but experiments show the albumin to be somewhat
less digestible and the soap-like product resulting not as valuable a
food as the fat. Such preparations have a high per cent of ash. There
is no objection from a nutritive point of view to a cocoa in which the
fat separates in oily globules.
221. Composition of Cocoa.--The cocoa bean, when dried or roasted and
freed from its husk and ground, is sold as cracked cocoa, or cocoa nibs.
From cocoa nibs the various cocoa and chocolate preparations are made.
Cocoas vary in composition according to the extent to which the fat is
removed during the process of manufacture and the nature and extent to
which other ingredients are added. An average cocoa contains about 20
per cent of proteids, and 30 per cent fat, also starch, sugar, gums,
fiber, and ash, as well as theobromine, a material very similar to
theine and caffein in tea and coffee, but not such an active stimulant.
Cocoa is not easily soluble, but it may be ground so fine that a long
time is required for its sedimentation; or sugar or other soluble
material may be added during the process of manufacture to increase the
specific gravity of the liquid to such an extent that the same object is
attained without such fine grinding. The first method is to be
preferred. Cocoa and its preparations are richer in nutritive substances
than tea and coffee and have this added advantage that both the soluble
and insoluble portions become a part of the beverage. Owing to the small
amount used for a cup of cocoa, independent of the milk it does not add
much in the way of nutrients to the ration.
222. Chocolate.--Plain chocolate is prepared from cocoa nibs without
"removal of the fat or other constituents except the germ." It differs
in chemical composition from cocoa by containing more fat and less
protein; it has nearly the same chemical composition as the cocoa nibs.
It is officially defined as containing "not more than 3 per cent of ash
insoluble in water, 3-1/2 per cent of crude fiber and 9 per cent of
starch, and less than 45 per cent cocoa fat."[71]
By the addition of sugar, sweet chocolates are made. They vary widely in
composition according to the flavors and amounts of sugar added during
their preparation. The average composition of cocoa nibs, standard
cocoa, and plain chocolate is as follows:
==============================================================
| COCOA | COMPOSITION OF | COMPOSITION OF
| NIBS | STANDARD COCOA | PLAIN CHOCOLATE
|---------------------------------------------
|Per Cent| Per Cent | Per Cent
Water | 3.00 | -- | 3.09
Ash | 3.50 | 4.20 | 3.08
Theobromine | 1.00 | -- | --
Caffein | 0.50 | -- | --
Crude Protein | 12.00 | -- | --
Crude fiber | 2.50 | 5.02 | 2.63
Fat | 50.00 | 32.52 | 49.81
Starch and other| | |
non-nitrogenous| | |
matter | 27.50 | -- | --
============================================================
223. Adulteration of Chocolate and Cocoa.--The various chocolate and
cocoa preparations offer an enticing field for sophistication; they are
not, however, so extensively adulterated as before the enforcement of
national and state pure food laws. The most common adulterants are
starch, cocoa shells, and occasionally iron dioxid and other pigments to
give color, also foreign fats to replace the fat removed and to give the
required plasticity for molding.
224. Comparative Composition of Beverages.--Tea and coffee as
beverages contain but little in the way of nutrients other than the
cream and sugar used in them. The solid matter in tea and coffee
infusions amounts to less than 1.2 per cent. When cocoa is made with
milk, it is a beverage of high nutritive value due mainly to the milk.
COMPOSITION OF BEVERAGES[56]
=============================================================================
| | | | | FUEL
KIND OF BEVERAGE | WATER | PROTEIN | FAT | CARBO- | VALUE
| | | | HYDRATES | PER LB.
------------------------|----------|----------|----------|----------|--------
| Per Cent | Per Cent | Per Cent | Per Cent |Calories
Commercial cereal coffee| | | | |
(0.5 ounce to | | | | |
1 pint water) | 98.2 | 0.2 | -- | 1.4 | 30
Parched corn coffee | | | | |
(1.6 ounces to | | | | |
1 pint water) | 99.5 | 0.2 | -- | 0.5 | 13
Oatmeal water (1 ounce | | | | |
to 1 pint water) | 99.7 | 0.3 | -- | 0.3 | 11
Coffee (1 ounce | | | | |
1 pint water) | 98.9 | 0.2 | -- | 0.7 | 16
Tea (0.5 ounce to | | | | |
1 pint water) | 99.5 | 0.2 | -- | 0.6 | 15
Cocoa (0.5 ounce to | | | | |
1 pint milk) | 84.5 | 3.8 | 4.7 | 6.0 | 365
Cocoa (0.5 ounce to | | | | |
1 pint water) | 97.1 | 0.6 | 0.9 | 1.1 | 65
Skimmed milk | 90.5 | 3.4 | 0.3 | 5.1 | 170
=============================================================================
CHAPTER XV
THE DIGESTIBILITY OF FOODS
225. Digestibility, How Determined.--The term "digestibility," as
applied to foods, is used in two ways: (1) meaning the thoroughness of
the process, or the completeness with which the nutrients of the food
are absorbed and used by the body, and (2) meaning the ease or comfort
with which digestion is accomplished. Cheese is popularly termed
indigestible, and rice digestible, when in reality the nutrients of
cheese are more completely although more slowly digested than those of
rice. In this work, unless otherwise stated, digestibility is applied to
the completeness of the digestion process.
The digestibility of a food is ascertained by means of digestion
experiments, in which all of the food consumed for a certain period,
usually two to four days, is weighed and analyzed, and from the weight
and composition is determined the amount, in pounds or grams, of each
nutrient consumed.[72] In like manner the nutrients in the indigestible
portion, or feces, are determined from the weight and composition of the
feces. The indigestible nutrients in the feces are deducted from the
total nutrients of the food, the difference being the amount digested,
or oxidized in the body. When the food is digested, the various
nutrients undergo complete or partial oxidation, with the formation of
carbon dioxid gas, water, urea (CH_{4}N_{2}O), and other compounds. The
feces consist mainly of the compounds which have escaped digestion. The
various groups of compounds of foods do not all have the same
digestibility; for example, the starch of potatoes is 92 per cent
digestible, while the protein is only 72 per cent. The percentage amount
of a nutrient that is digested is called the digestion coefficient.
In the following way the digestibility of a two-days ration of bread and
milk was determined: 773.5 grams of bread and 2000 grams of milk were
consumed by the subject. The dried feces weighed 38.2 grams. The foods
and feces when analyzed were found to have the following
composition:[62]
=====================================================================
COMPOSITION | BREAD | MILK | FECES[A]
---------------------------------------------------------------------
Water | 44.13 | 86.52 | --
Crude protein | 7.75 | 3.15 | 25.88
Ether extract | 0.90 | 4.63 | 18.23
Ash | 0.32 | 0.70 | 26.35
Carbohydrates | 46.90 | 5.00 | 29.54
Calories per gram | 2.450 | 0.79 | 5.083
=====================================================================
[Footnote A: Results on dry-matter basis.]
STATEMENT OF RESULTS OF A DIGESTION EXPERIMENT
=============================================================================
FOOD CONSUMED | WEIGHT | PROTEIN | ETHER | CARBO- | | HEAT OF
| OF | N × 6.25 | EXTRACT | HY- | ASH | COMBUS-
| MATERIAL | | | DRATES | | TION
------------------+----------+----------+---------+--------+-------+---------
| Grams | Grams | Grams | Grams | Grams | Calories
Bread | 773.5 | 60.0 | 6.9 | 362.8 | 2.5 | 1895
Milk | 2000.0 | 63.0 | 92.6 | 100.0 | 14.0 | 1585
| | ------- + ------- + -------+-------+---------
Total | 38.2 | 123.0 | 99.5 | 462.8 | 16.5 | 3480
Feces | | 9.9 | 7.0 | 11.3 | 10.1 | 194
| | ------- + ------- + -------+-------+---------
Total amount | | 113.1 | 92.5 | 451.5 | 6.4 | 3286
digested | | | | | |
Per cent digested | | | | | |
or coefficients | | | | | |
of digestibility| | 92.0 | 93.0 | 97.5 | 38.8 | 94.4
| | | | | |
Available energy | | -- | -- | -- | -- | 90.0
=============================================================================
In this experiment 92 per cent of the crude protein, 93 per cent of the
ether extract, and 97.5 per cent of the carbohydrates of the bread and
milk ration were digested and absorbed by the body. In calculating the
available energy, correction is made for the unoxidized residue, as urea
and allied forms. It is estimated that for each gram of protein in the
ration there was an indigestible residue yielding 1.25 calories.
226. Available Nutrients.--A food may contain a comparatively large
amount of a compound, and yet, on account of its low digestibility, fail
to supply much of it to the body in an available form. Hence it is that
the value of a food is dependent not alone on its composition, but also
on its digestibility. The digestible or available nutrients of a food
are determined by multiplying the per cent of each nutrient which the
food contains by its digestion coefficient. For example, a sample of
wheat flour contains 12 per cent protein, 88 per cent of which is
digestible, making 10.56 per cent of available or digestible protein (12
× 0.88-10.56). Graham flour made from similar wheat contains 13 per cent
total protein, and only 75 per cent of the protein is digestible, making
9.75 per cent available (13 × 0.75 = 9.75). Thus one food may contain a
larger total but a smaller available amount of a nutrient than another.
227. Available Energy.--The available energy of a food or a ration is
expressed in calories. A ration for a laborer at active out-of-door work
should yield about 3200 calories. The calory is the unit of heat, and
represents the heat required to raise the temperature of a kilogram of
water 1° C., or four pounds of water 1° F. The caloric value of foods is
determined by the calorimeter, an apparatus which measures heat with
great accuracy. A pound of starch, or allied carbohydrates, yields 1860
calories, and a pound of fat 4225 (see Section 13). While a gram of
protein completely burned produces 7.8 calories, digested it yields only
about 4.2 calories, because, as explained in the preceding section, not
all of the carbon and oxygen are oxidized.[59] The caloric value or
available energy of a ration can be calculated from the digestible
nutrients by multiplying the pounds of digestible protein and
carbohydrates by 1860, the digestible fat by 4225, and adding the
results. For determination of the available energy of foods under
different experimental conditions, and where great accuracy is desired,
a specially constructed respiration calorimeter has been devised, which
is built upon the same principle as an ordinary calorimeter, except it
is large enough to admit a person, and is provided with appliances for
measuring and analyzing the intake and outlet of air.[74] The heat
produced by the combustion of the food in the body warms the water
surrounding the calorimeter chamber, and this increase in temperature is
determined by thermometers reading to 0.005 of a degree or less.
[Illustration: FIG. 55.--CALORIMETER.]
228. Normal Digestion and Health.--While the process of digestion has
been extensively studied, it is not perfectly understood. Between the
initial compounds of foods and their final oxidation products a large
number of intermediate substances are formed, and when digestion fails
to take place in a normal way, toxic or poisonous compounds are produced
and various diseases result. It is probable that more diseases are due
to imperfect or malnutrition than to any other cause. There is a very
close relationship between health and normal digestion of the food.
The cells in the different parts of the digestive tract secrete fluids
containing substances known as soluble ferments, or enzymes, which act
upon the various compounds of foods, changing them chemically and
physically so that they can be absorbed and utilized by the body. (See
Section 31.) Some of the more important ferments are: ptyolin of the
saliva, pepsin of the stomach, and pancreatin and diastase of the
intestines. In order that these ferments may carry on their work in a
normal way, the acidity and alkalinity of the different parts of the
digestive tract must be maintained. The gastric juice contains from 0.1
to 0.25 per cent of hydrochloric acid, imparting mildly antiseptic
properties; and while the peptic ferment works in a slightly acid
solution, the tryptic ferment requires an alkaline solution. To secrete
the necessary amount and quality of digestive fluids, the organs must be
in a healthy condition. Many erroneous ideas regarding the digestion of
foods are based upon misinterpretation of facts by persons suffering
from impaired digestion, and attempts are frequently made to apply to
normal digestion generalizations applicable only to diseased conditions.
229. Digestibility of Animal Foods.--The proteids and fats in animal
foods, as meats, are more completely digested than the same class of
nutrients in vegetables. In general, about 95 per cent of the proteids
of meats is digestible, while those in vegetables are often less than 85
percent digestible. The amount of indigestible residue from animal foods
is small; while from vegetables it is large, for the cellulose prevents
complete absorption of the nutrients and, as a result, there is much
indigestible residue. Animal foods are concentrated, in that they
furnish large amounts of nutrients in digestible forms. There is less
difference in the completeness with which various meats are digested
than in their ease of digestion; the proteins all have about the same
digestion coefficients, but vary with individuals as to ease of
digestion and time required. It is generally considered that the
digestible proteins, whether of animal or vegetable origin, are equally
valuable for food purposes. This is an assumption, however, that has not
been well established by experimental evidence. In a mixed ration, the
proteins from different sources appear to have the same nutritive value,
but as each is composed of different radicals and separated into
dissimilar elementary compounds during the process of digestion, they
would not necessarily all have the same food value.
There is but little difference between the fats and proteins of meats as
to completeness of digestion,--the slight difference being in favor of
the proteins. Some physiologists claim that the fat, which in some meats
surrounds the bundles of fiber (protein), forming a protecting coat,
prevents the complete solvent action of the digestive fluid. Very fat
meats are not as completely digested as those moderately fat. It is also
claimed that the digestibility of the meat is influenced by the
mechanical character, as toughness of the fiber.
230. Digestibility of Vegetable Foods.--Vegetable foods vary in
digestibility with their mechanical condition and the amount of
cellulose or fiber. In some the nutrients are so embedded in cellular
tissue as to be protected from the solvent action of the digestive
fluids, and in such cases the digestibility and availability are low.
The starches and sugars are more completely digested than any other of
the nutrients of vegetables; in some instances they are from 95 to 98
per cent digestible. Some cellular tissue, but not an excess, is
desirable in a ration, as it exerts a favorable mechanical action upon
the organs of digestion, encourages peristalsis, and is an absorbent and
dilutant of the waste products formed during digestion. For example, in
the feeding of swine, it has been found that corn and cob meal often
gives better results than corn fed alone. The cob contains but little in
the way of nutrients, but it exerts a favorable mechanical action upon
digestion. Occasionally too many bulky foods are combined, containing
scant amounts of nutrients, so that the body receives insufficient
protein. This is liable to be the case in the dietary of the strict
vegetarian. Many of the vegetables possess special dietetic value, due
to the organic acids and essential oils, as cited in the chapter on
fruits and vegetables. The value of such foods cannot always be
determined from their content of digestible protein, fat, and
carbohydrates. This is particularly evident when they are omitted from
the ration, as in the case of a restricted diet consisting mainly of
animal foods. Many vegetables have low nutritive value on account of
their bulky nature and the large amount of water and cellulose which
they contain, which tends to decrease digestibility and lower the amount
of available nutrients. Because of their bulk and fermentable nature,
resulting in the formation of gases, a diet of coarse vegetables has a
tendency to cause distention and enlargement of the intestinal organs.
The carbohydrates, which are the chief constituents of vegetables, are
digested mainly in the intestines, and require special mechanical
preparation in the stomach, hence the nutrients of vegetables are not,
as a rule, as easily digested as those of animal foods.
231. Factors influencing Digestion.--There are a number of factors
which influence completeness as well as ease of digestion, as: (1)
combination of foods; (2) amount of food; (3) method of preparation; (4)
mechanical condition of the food; (5) palatability; (6) physiological
properties; (7) individuality of the consumer; and (8) psychological
influences.
232. Combination of Foods.--In a mixed ration the nutrients are
generally more completely digested than when only one food is used. For
example, milk is practically all digested when it forms a part of a
ration, and it also promotes digestibility of the foods with which it is
combined, but when used alone it is less digestible.[27] Bread alone and
milk alone are not as completely digested as bread and milk combined.
The same in a general way has been observed in the feeding of farm
animals,--better results are secured from combining two or more foods
than from the use of one alone. The extent to which one food influences
the digestibility of another has not been extensively studied.
In a mixed ration, consisting of several articles of food of different
mechanical structure, the work of digestion is more evenly distributed
among the various organs. A food often requires special preparation on
the part of the stomach before it can be digested in the intestines, and
if this food is consumed in small amounts and combined with others of
different structure, the work of gastric digestion is lessened so that
the foods are properly prepared and normal digestion takes place. The
effect which one food exerts upon the digestibility of another is
largely mechanical.
233. Amount of Food.--Completeness as well as ease of digestion is
influenced by the amount of food consumed. In general, excessive amounts
are not as completely digested as moderate amounts. In digestion
experiments with oatmeal and milk, it was found that when these foods
were consumed in large quantities the fat and protein were not as
completely absorbed by the body as when less was used, the protein being
7 per cent and the fat 6 per cent more digestible in the medium ration.
Experiments with animals show that economical results are not secured
from an excess of food.[5] Some individuals consume too much food, and
with them a restricted diet would be beneficial, while others err in not
consuming enough to meet the requirements of the body. Quite frequently
it is those who need more food who practice dieting. When there is
trouble with digestion, it is not always the amount or kind of food
which is at fault, but other habits may be such as to affect digestion.
The active out-of-door laborer can with impunity consume more food,
because there is greater demand for nutrients, and the food is more
completely oxidized in the body and without the formation of poisonous
waste products. The amount of food consumed should be sufficient to meet
all the demands of the body and maintain a normal weight.
234. Method of Preparation of Food.--The extent to which methods of
cooking and preparation influence completeness of digestion has not been
extensively investigated. As is well known, they have great influence
upon ease and comfort of digestion. During cooking, as discussed in
Chapter II, extensive physical and chemical changes occur, and these in
turn affect digestibility. When the cooking has not been sufficient to
mechanically disintegrate vegetable tissue, the digestive fluids fail to
act favorably upon the food. Cooking is also beneficial because it
renders the food sterile and destroys all objectionable microörganisms
which, if they remain in food, readily undergo incubation in the
digestive tract, interfering with normal digestion. Prolonged heat
causes some foods to become less digestible, as milk, which digestion
experiments show to be more completely digested when fresh than when
sterilized. Pasteurized milk, which is not subjected to so high a
temperature as sterilized milk, is more completely digested. See Chapter
VII for discussion of sterilizing and pasteurizing milk.[38] The
benefits derived from the destruction of the objectionable bacteria in
foods are, however, greater than the losses attendant on lessened
digestibility due to the action of heat. The method of preparation of a
food affects its digestibility mainly through change in mechanical
structure, and modification of the forms in which the nutrients are
present.[5]
235. Mechanical Condition of Foods.--The mechanical condition of foods
as to density and structure of the particles and the extent to which
they are disintegrated in their preparation for the table influences
digestibility to a great extent. The mechanics of digestion is a subject
that has not been extensively investigated, and it is one of great
importance, as biological and chemical changes cannot take place if the
food is not in proper mechanical condition. In general, the finer the
food particles, the more completely the nutrients are acted upon by the
digestive fluids and absorbed by the body. Nevertheless, the diet should
not consist entirely of finely granulated foods. Some foods are valuable
mainly because of the favorable action they exert mechanically upon
digestion, rather than for the nutrients they contain.[62] Coarsely
granulated breakfast foods, whole wheat flour, and many vegetables
contain sufficient cellular tissue to give special value from a
mechanical rather than a chemical point of view. The extent to which
coarsely and finely granulated foods should enter into the ration is a
question largely for the individual to determine. Experiments with pigs
show that if large amounts of coarse, granular foods are consumed, the
tendency is for the digestive tract to become inflamed and less able to
exercise its normal functions. Coarsely granulated foods have a tendency
to pass through the digestive tract in less time than those that are
finely granulated, due largely to increased peristaltic action, and the
result is the food is not retained a sufficient length of time to allow
normal absorption to take place. In the feeding of farm animals, it has
been found that the mechanical condition of the food has a great
influence upon its economic use. Rations that are either too bulky or
too concentrated fail to give the best results. In the human ration, the
mechanical condition of the food is equally as important as its chemical
composition.
236. Mastication is an important part of digestion, and when foods are
not thoroughly masticated, additional work is required of the stomach,
which is usually an overworked organ because of doing the work of the
mouth as well. Although much of the mechanical preparation and mixing of
foods is of necessity done in the stomach, some of it may advantageously
be done in the mouth. The stomach should not be required to perform the
function of the gizzard of a fowl.
237. Palatability of Foods.--Many foods naturally contain essential
oils and other substances which impart palatability. These have but
little in the way of nutritive value, but they assist in rendering the
nutrients with which they are associated more digestible. Palatability
of a food favorably influences the secretion of the gastric and other
digestive fluids, and in this way the natural flavors of well-prepared
foods aid in digestion. In the feeding of farm animals it has been found
that when foods are consumed with a relish better returns are secured
than when unpalatable foods are fed. To secure palatability the
excessive use of condiments is unnecessary. It is possible to a great
extent during preparation to develop and conserve the natural flavors.
Some foods contain bitter principles which are removed during the
cooking, while in others pleasant flavors are developed. Palatability is
an important factor in the digestibility of foods.
238. Physiological Properties of Food.--Some food materials,
particularly fruits and vegetables, contain compounds which have
definite physiological properties, as tannin which is an astringent,
special oils which exert a cathartic action, and the alkaloids which
serve as irritants to nerve centers. Wheat germ oil is laxative, and it
is probable that the physiological properties of graham and whole wheat
breads are due in some degree to the oil which they contain.[67] The
use of fruits, herbs, and vegetables for medicinal purposes is based
upon the presence of compounds possessing well-defined medicinal
properties. As a rule food plants do not contain appreciable amounts of
such substances, and the use of food for medicinal effect should be by
the advice of a physician. The physiological properties of some foods
are due to bacterial products. See Chapter XX.
239. Individuality.--Material difference in digestive power is
noticeable among individuals. Digestion experiments show that one person
may digest 5 per cent more of a nutrient than another. This difference
appears to be due to a number of factors, as activity of the organs, as
affected by exercise and kind of labor performed; abnormal composition
of the digestive fluids; or failure of the different parts of the
digestive tract to act in harmony. Individuality is one of the most
important factors in digestion. Persons become accustomed to certain
foods through long usage, and the digestive tract adapts itself to those
foods, rendering sudden and extreme changes in the dietary hazardous.
Common food articles may fail to properly digest in the case of some
individuals, while with others they are consumed with benefit. What is
food to one may prove to be a poison to another, and while general
statements can be made in regard to the digestibility of foods,
individual differences must be recognized.
240. Psychological Factors.--Previously conceived ideas concerning
foods influence digestibility. Foods must be consumed with a relish in
order to secure the best results, as flow of the digestive fluids and
activity of the organs are to a certain extent dependent upon the nerve
centers. If it is believed that a food is poisonous or injurious, even
when the food is wholesome, normal digestion fails to take place. In
experiments by the author, in which the comparative digestibility of
butter and oleomargarine was being studied, it was found that when the
subjects were told they were eating oleomargarine, its digestibility was
depressed 5 per cent, and when they were not told the nature of the
material, but assumed that butter was oleomargarine, the digestibility
of the butter was lowered about 6 per cent.[13] Preconceived notions in
regard to foods, not founded upon well-established facts, but due to
prejudice resulting from ignorance, cause many valuable foods to be
excluded from the dietary. Many persons, like the foreign lady who,
visiting this country, said she ate only acquaintances, prefer foods
that have a familiar taste and appearance, and any unusual taste or
appearance detracts from the value because of the psychological
influence upon digestion.
CHAPTER XVI
COMPARATIVE COST AND VALUE OF FOODS
241. Cost and Nutrient Content of Foods.--The market price and the
nutritive value of foods are often at variance, as those which cost the
most frequently contain the least nutrients.[75] It is difficult to make
absolute comparisons as to the nutritive value of foods at different
prices, because they differ not only in the amounts, but also in the
kinds of nutrients. While it is not possible to express definitely the
value of one food in terms of another, approximate comparisons may be
made as to the amounts of nutrients that can be secured for a given sum
of money when foods are at different prices, and tables have been
prepared making such comparisons.
[Illustration: FIG. 56.--COMPOSITION OF FOODS.
(From Office of Experiment Stations Bulletin.)]
242. Nutrients Procurable for a Given Sum.[7]--To ascertain the
nutrients procurable for a given sum first determine the amount in
pounds that can be obtained, say, for ten cents, and then multiply by
the percentages of fat, protein, carbohydrates, and calories in the
food. The results are the amounts, in pounds, of nutrients procurable
for that sum of money. For example: if milk is 5 cents per quart, two
quarts or approximately four pounds, can be procured for 10 cents. If
the milk contains fat, 4 per cent, protein, 3.3 per cent, carbohydrates,
5 per cent, and fuel value, 310 calories per pound, multiplying each of
these by 4 gives the nutrients and fuel value in four pounds, or 10
cents worth of milk, as follows:
Protein 0.13 lb.
Fat 0.16 lb.
Carbohydrates 0.2 lb.
Calories 1240
If it is desired to compare milk at 5 cents per quart with round steak
at 15 cents per pound, 10 cents will procure 0.66, or two thirds of a
pound of round steak containing on an average (edible portion) 19 per
cent protein, 12.8 per cent fat, and yielding 890 calories per pound. If
10 per cent is refuse, there is edible about 0.6 of a pound. The amounts
of nutrients in the 0.6 of a pound of steak, edible portion, or 0.66 lb.
as purchased would be:
Protein 0.11 lb.
Fat 0.08 lb.
Calories 534
It is to be observed that from the 10 cents' worth of milk a little more
protein, 0.08 of a pound more fat, and nearly two and one half times as
many calories can be secured as from the 10 cents' worth of meat. This
is due to the carbohydrates and the larger amount of fat which the milk
contains. At these prices, milk should be used liberally in the dietary,
as it furnishes more of all the nutrients than does meat. It would not
be advisable to exclude meat entirely from the ration, but milk at 5
cents per quart is cheaper food than meat at 15 cents per pound. In
making comparisons, preference cannot always be given to one food
because of its containing more of any particular nutrient, for often
there are other factors that influence the value.
243. Comparing Foods as to Nutritive Value.--In general, preference
should be given to foods which supply the most protein, provided the
differences between the carbohydrates and fats are not large. When the
protein content of two foods is nearly the same, but the fats and
carbohydrates differ materially, the preference may safely be given to
the food which supplies the larger amount of total nutrients. A pound of
protein in a ration is more valuable than a pound of either fat or
carbohydrates, although it is not possible to establish an absolute
scale as to the comparative value of these nutrients, because they serve
different functional purposes in the body. It is sometimes necessary to
use small amounts of foods rich in protein in order to secure a balanced
ration; excessive use of protein, however, is not economical, as that
which is not needed for functional purposes is converted into heat and
energy which could be supplied as well by the carbohydrates, and they
are less expensive nutrients.
[Illustration: FIG. 57.--PECUNIARY ECONOMY OF FOOD.
(From Office of Experiment Stations Bulletin.)]
TEN CENTS WILL PURCHASE: (From Farmer's Bulletin No. 142, U. S.
Dept. of Agr.)
=============================================================================
| | TOTAL | | | |
| | WEIGHT | | | |
KIND OF FOOD | PRICE | OF FOOD | | | CAR- |
MATERIAL | PER | MATE- |PROTEIN | FAT | BOHY- | ENERGY
| POUND | RIAL | | | DRATES |
------------------------+-------+---------+--------+-------+---------+-------
| Cents | Pounds | Pound | Pound | Pounds |Calories
Beef, sirloin | 25 | 0.40 | 0.06 | 0.06 | -- | 410
Do. | 20 | 0.50 | 0.08 | 0.08 | -- | 515
Do. | 15 | 0.67 | 0.10 | 0.11 | -- | 685
Beef, round | 16 | 0.63 | 0.11 | 0.08 | -- | 560
Do. | 14 | 0.71 | 0.13 | 0.09 | -- | 630
Do. | 12 | 0.83 | 0.15 | 0.10 | -- | 740
Beef, shoulder clod | 12 | 0.83 | 0.13 | 0.08 | -- | 595
Do. | 9 | 1.11 | 0.18 | 0.10 | -- | 795
Beef, stew meat | 5 | 2.00 | 0.29 | 0.23 | -- | 1530
Beef, dried, chipped | 25 | 0.40 | 0.10 | 0.03 | -- | 315
Mutton chops, loin | 16 | 0.63 | 0.08 | 0.17 | -- | 890
Mutton, leg | 20 | 0.50 | 0.07 | 0.07 | -- | 445
Do. | 16 | 0.63 | 0.09 | 0.09 | -- | 560
Roast pork, loin | 12 | 0.83 | 0.11 | 0.19 | -- | 1035
Pork, smoked ham | 22 | 0.45 | 0.06 | 0.14 | -- | 735
Do. | 18 | 0.56 | 0.08 | 0.18 | -- | 915
Pork, fat salt | 12 | 0.83 | 0.02 | 0.68 | -- | 2950
Codfish, dressed, fresh | 10 | 1.00 | 0.11 | -- | -- | 220
Halibut, fresh | 18 | 0.56 | 0.08 | 0.02 | -- | 265
Cod, salt | 7 | 1.43 | 0.22 | 0.01 | -- | 465
Mackerel, salt, dressed | 10 | 1.00 | 0.13 | 0.20 | -- | 1135
Salmon, canned | 12 | 0.83 | 0.18 | 0.10 | -- | 760
Oysters, solids, | | | | | |
50 cents per quart | 25 | 0.40 | 0.02 | -- | 0.01 | 90
35 cents per quart | 18 | 0.56 | 0.03 | 0.01 | 0.02 | 125
Lobster, canned | 18 | 0.56 | 0.10 | 0.01 | -- | 225
Butter | 20 | 0.50 | 0.01 | 0.40 | -- | 1705
Do. | 25 | 0.40 | -- | 0.32 | -- | 1365
Do. | 30 | 0.33 | -- | 0.27 | -- | 1125
Eggs, 36 cents per dozen| 24 | 0.42 | 0.05 | 0.04 | -- | 260
Eggs, 24 cents per dozen| 16 | 0.63 | 0.07 | 0.06 | -- | 385
Eggs, 12 cents per dozen| 8 | 1.25 | 0.14 | 0.11 | -- | 770
Cheese | 16 | 0.63 | 0.16 | 0.20 | 0.02 | 1185
Milk, 7 cents per quart | 3-1/2 | 2.85 | 0.09 | 0.11 | 0.14 | 885
Milk, 6 cents per quart | 3 | 3.33 | 0.11 | 0.13 | 0.17 | 1030
Wheat flour | 3 | 3.33 | 0.32 | 0.03 | 2.45 | 5440
Do. | 2-1/2 | 4.00 | 0.39 | 0.04 | 2.94 | 6540
Corn meal, granular | 2-1/2 | 4.00 | 0.31 | 0.07 | 2.96 | 6540
Wheat breakfast food | 7-1/2 | 1.33 | 0.13 | 0.02 | 0.98 | 2235
Oat breakfast food | 7-1/2 | 1.33 | 0.19 | 0.09 | 0.86 | 2395
Oatmeal | 4 | 2.50 | 0.34 | 0.16 | 1.66 | 4500
Rice | 8 | 1.25 | 0.08 | -- | 0.97 | 2025
Wheat bread | 6 | 1.67 | 0.13 | 0.02 | 0.87 | 2000
Do. | 5 | 2.00 | 0.16 | 0.02 | 1.04 | 2400
Do. | 4 | 2.50 | 0.20 | 0.03 | 1.30 | 3000
Rye bread | 5 | 2.00 | 0.15 | 0.01 | 1.04 | 2340
Beans, white, dried | 5 | 2.00 | 0.35 | 0.03 | 1.16 | 3040
Cabbage | 2-1/2 | 4.00 | 0.05 | 0.01 | 0.18 | 460
Celery | 5 | 2.00 | 0.02 | -- | 0.05 | 130
Corn, canned | 10 | 1.00 | 0.02 | 0.01 | 0.18 | 430
Potatoes, | | | | | |
90 cents per bushel | 1-1/2| 6.67 | 0.10 | 0.01 | 0.93 | 1970
60 cents per bushel | 1 | 10.00 | 0.15 | 0.01 | 1.40 | 2950
45 cents per bushel | 3/4 | 13.33 | 0.20 | 0.01 | 1.87 | 3935
Turnips | 1 | 10.00 | 0.08 | 0.01 | 0.54 | 1200
Apples | 1-1/2| 6.67 | 0.02 | 0.02 | 0.65 | 1270
Bananas | 7 | 1.43 | 0.01 | 0.01 | 0.18 | 370
Oranges | 6 | 1.67 | 0.01 | -- | 0.13 | 250
Strawberries | 7 | 1.43 | .01 | 0.01 | 0.09 | 215
Sugar | 6 | 1.67 | -- | -- | 1.67 | 2920
=============================================================================
It is to be noted in the table that, ordinarily, for the same amount of
money the most nutrients can be obtained in the form of milk, cheese,
sugar, and beans, corn meal, wheat flour, oatmeal, and cereals in bulk.
While meats supply protein liberally, they fail to furnish carbohydrates
as the vegetables. As discussed in the chapter on Dietary Studies of
Families, unnecessarily expensive foods are often used, resulting either
in lack of nutrients or unbalanced rations.
EXAMPLES
1. Compute the calories and the amounts of protein, fat, and
carbohydrates that can be procured for 25 cents in cheese selling for 18
cents per pound; how do these compare with the nutrients in eggs at 20
cents per dozen?
2. Which food furnishes the larger amount of nutrients, potatoes at 50
cents per bushel or flour at $6 per barrel?
3. How do beans at 10 cents per quart compare in nutritive value with
beef at 15 Cents per pound?
4. How does salt codfish at 10 cents per pound compare in nutritive
value with lamb chops at 15 cents per pound?
5. Compare in nutritive value cream at 25 cents per quart with butter at
30 cents per pound.
6. Calculate the composition and nutritive value of a cake made of
sugar, 8 oz.; butter, 4 oz.; eggs, 8 oz.; flour, 8 oz.; and milk, 4 oz.;
the baked cake weighs one and three fourths pounds.
AVERAGE COMPOSITION OF COMMON AMERICAN FOOD PRODUCTS
(From Farmer's Bulletin, No. 142, U. S. Dept. of Agr.)
=============================================================================
| | | | | | | F
| | | | | h | | u p
| R | | P | | C y | | e e
| e | W | r | | a d | | l r
| f | a | o | F | r r | A |
Food Material | u | t | t | a | b a | s | v P
(as purchased) | s | e | e | t | o t | h | a o
| e | r | i | | - e | | l u
| | | n | | s | | u n
| | | | | | | e d
------------------------------+------+------+------+------+-----+-----+------
| | | | | | | Calo-
ANIMAL FOOD | % | % | % | % | % | % | ries
| | | | | | |
Beef, fresh: | | | | | | |
Chuck ribs | 16.3 | 52.6 | 15.5 | 15.0 | -- | 0.8 | 910
Flank | 10.2 | 54.0 | 17.0 | 19.0 | -- | 0.7 | 1105
Loin | 13.3 | 52.5 | 16.1 | 17.5 | -- | 0.9 | 1025
Porterhouse steak | 12.7 | 52.4 | 19.1 | 17.9 | -- | 0.8 | 1100
Sirloin steak | 12.8 | 54.0 | 16.5 | 16.1 | -- | 0.9 | 975
Neck | 27.6 | 45.9 | 14.5 | 11.9 | -- | 0.7 | 1165
Ribs | 20.8 | 43.8 | 13.9 | 21.2 | -- | 0.7 | 1135
Rib rolls | -- | 63.9 | 19.3 | 16.7 | -- | 0.9 | 1055
Round | 7.2 | 60.7 | 19.0 | 12.8 | -- | 1.0 | 890
Rump | 20.7 | 45.0 | 13.8 | 20.2 | -- | 0.7 | 1090
Shank, fore | 36.9 | 42.9 | 12.8 | 7.3 | -- | 0.6 | 545
Shoulder and clod | 16.4 | 56.8 | 16.4 | 9.8 | -- | 0.9 | 715
Fore quarter | 18.7 | 49.1 | 14.5 | 17.5 | -- | 0.7 | 995
Hind quarter | 15.7 | 50.4 | 15.4 | 18.3 | -- | 0.7 | 1045
Beef, corned, canned, | | | | | | |
pickled, dried: | | | | | | |
Corned beef | 8.4 | 49.2 | 14.3 | 23.8 | -- | 4.6 | 1245
Tongue, pickled | 6.0 | 58.9 | 11.9 | 19.2 | -- | 4.3 | 1010
Dried, salted, and smoked | 4.7 | 53.7 | 26.4 | 6.9 | -- | 8.9 | 790
Canned boiled beef | -- | 51.8 | 25.5 | 22.5 | -- | 1.3 | 1410
Canned corned beef | -- | 51.8 | 26.3 | 18.7 | -- | 4.0 | 1270
Veal: | | | | | | |
Breast | 21.3 | 52.0 | 15.4 | 11.0 | -- | 0.8 | 745
Leg | 14.2 | 60.1 | 15.5 | 7.9 | -- | 0.9 | 625
Leg cutlets | 3.4 | 68.3 | 20.1 | 7.5 | -- | 1.0 | 695
Fore quarter | 24.5 | 54.2 | 15.1 | 6.0 | -- | 0.7 | 535
Hind quarter | 20.7 | 56.2 | 16.2 | 6.6 | -- | 0.8 | 580
Mutton: | | | | | | |
Flank | 9.9 | 39.0 | 13.8 | 36.9 | -- | 0.6 | 1770
Leg, hind | 18.4 | 51.2 | 15.1 | 14.7 | -- | 0.8 | 890
Loin chops | 16.0 | 42.0 | 13.5 | 28.3 | -- | 0.7 | 1415
Fore quarter | 21.2 | 41.6 | 12.3 | 24.5 | -- | 0.7 | 1235
Hind quarter, without | 17.2 | 45.4 | 13.8 | 23.2 | -- | 0.7 | 1210
tallow | | | | | | |
Lamb: | | | | | | |
Breast | 10.1 | 45.5 | 15.4 | 19.1 | -- | 0.8 | 1075
Leg, hind | 17.4 | 52.9 | 15.9 | 13.6 | -- | 0.9 | 860
Pork, fresh: | | | | | | |
Ham | 10.7 | 48.0 | 13.5 | 25.9 | -- | 0.8 | 1320
Loin chops | 19.7 | 41.8 | 13.4 | 24.2 | -- | 0.8 | 1245
Shoulder | 12.4 | 44.9 | 12.0 | 29.8 | -- | 0.7 | 1450
Tenderloin | -- | 66.5 | 18.9 | 13.0 | -- | 1.0 | 895
Pork, salted, cured, pickled: | | | | | | |
Ham, smoked | 13.6 | 34.8 | 14.2 | 33.4 | -- | 4.2 | 1635
Shoulder, smoked | 18.2 | 36.8 | 13.0 | 26.6 | -- | 5.5 | 1335
Salt pork | -- | 7.9 | 1.9 | 86.2 | -- | 3.9 | 3555
Bacon, smoked | 7.7 | 17.4 | 9.1 | 62.2 | -- | 4.1 | 2715
Sausage: | | | | | | |
Bologna | 3.3 | 55.2 | 18.2 | 19.7 | -- | 3.8 | 1155
Pork | -- | 39.8 | 13.0 | 44.2 | 1.1| 2.2 | 2075
Frankfort | -- | 57.2 | 19.6 | 18.6 | 1.1| 3.4 | 1155
Soups: | | | | | | |
Celery, cream of | -- | 88.6 | 2.1 | 2.8 | 5.0| 1.5 | 235
Beef | -- | 92.9 | 4.4 | 0.4 | 1.1| 1.2 | 120
Meat stew | -- | 84.5 | 4.6 | 4.3 | 5.5| 1.1 | 365
Tomato | -- | 90.0 | 1.8 | 1.1 | 5.6| 1.5 | 185
Poultry: | | | | | | |
Chicken, broilers | 41.6 | 43.7 | 12.8 | 1.4 | -- | 0.7 | 305
Fowls | 25.9 | 47.1 | 13.7 | 12.3 | -- | 0.7 | 765
Goose | 17.6 | 38.5 | 13.4 | 29.8 | -- | 0.7 | 1475
Turkey | 22.7 | 42.4 | 16.1 | 18.4 | -- | 0.8 | 1060
Fish: | | | | | | |
Cod, dressed | 29.9 | 58.5 | 11.1 | 0.2 | -- | 0.8 | 220
Halibut, steaks or sections | 17.7 | 61.9 | 15.3 | 4.4 | -- | 0.9 | 475
Mackerel, whole | 44.7 | 40.4 | 10.2 | 4.2 | -- | 0.7 | 370
Perch, yellow dressed | 35.1 | 50.7 | 12.8 | 0.7 | -- | 0.9 | 275
Shad, whole | 50.1 | 35.2 | 9.4 | 4.8 | -- | 0.7 | 380
Shad, roe | -- | 71.2 | 20.9 | 3.8 | 2.6| 1.5 | 600
Fish, preserved: | | | | | | |
Cod, salt | 24.9 | 40.2 | 16.0 | 0.4 | -- |18.5 | 325
Herring, smoked | 44.4 | 19.2 | 20.5 | 8.8 | -- | 7.4 | 755
Fish, canned | | | | | | |
Salmon | -- | 63.5 | 21.8 | 12.1 | -- | 2.6 | 915
Sardines |[A]5.0| 53.6 | 23.7 | 12.1 | -- | 5.3 | 950
Shellfish: | | | | | | |
Clams | -- | 80.8 | 10.6 | 1.1 | 5.2 | 2.3| 340
Crabs | 52.4 | 36.7 | 7.9 | 0.9 | 0.6 | 1.5| 200
Lobsters | 61.7 | 30.7 | 5.9 | 0.7 | 0.2 | 0.8| 145
Eggs: Hen's eggs [B]|11.2 | 65.5 | 13.1 | 9.3 | -- | 0.9| 635
Dairy products, etc.: | | | | | | |
Butter | -- | 11.0 | 1.0 |85.0 | -- | 3.0| 3410
Whole milk | -- | 87.0 | 3.3 | 4.0 | 5.0 | 0.7| 310
Skim milk | -- | 90.5 | 3.4 | 0.3 | 5.1 | 0.7| 165
Buttermilk | -- | 91.0 | 3.0 | 0.5 | 4.8 | 0.7| 160
Condensed milk | -- | 26.9 | 8.8 | 8.3 |54.1 | 1.9| 1430
Cream | -- | 74.0 | 2.5 |18.5 | 4.5 | 0.5| 865
Cheese, Cheddar | -- | 27.4 | 27.7 |36.8 | 4.1 | 4.0| 2075
Cheese, full cream | -- | 34.2 | 25.9 |33.7 | 2.4 | 3.8| 1885
| | | | | | |
VEGETABLE FOOD | | | | | | |
| | | | | | |
Flour, meal, etc.: | | | | | | |
Entire wheat flour | -- | 11.4 | 13.8 | 1.9 |71.9 | 1.0| 1650
Graham flour | -- | 11.3 | 13.3 | 2.2 |71.4 | 1.8| 1645
Wheat flour, patent | | | | | | |
roller process | | | | | | |
High-grade and medium | -- | 12.0 | 11.4 | 1.0 |75.1 | 0.5| 1635
Low grade | -- | 12.0 | 14.0 | 1.9 |71.2 | 0.9| 1640
Macaroni, vermicelli, etc | -- | 10.3 | 13.4 | 0.9 |74.1 | 1.3| 1645
Wheat breakfast food | -- | 9.6 | 12.1 | 1.8 |75.2 | 1.3| 1680
Buckwheat flour | -- | 13.6 | 6.4 | 1.2 |77.9 | 0.9| 1605
Rye flour | -- | 12.9 | 6.8 | 0.9 |78.7 | 0.7| 1620
Corn meal | -- | 12.5 | 9.2 | 1.9 |75.4 | 1.0| 1635
Oat breakfast food | -- | 7.7 | 16.7 | 7.3 |66.2 | 2.1| 1800
Rice | -- | 12.3 | 8.0 | 0.3 |79.0 | 0.4| 1620
Tapioca | -- | 11.4 | 0.4 | 0.1 |88.0 | 0.1| 1650
Starch | -- | -- | -- | -- |90.0 | -- | 1675
Bread, pastry, etc.: | | | | | | |
White bread | -- | 35.3 | 9.2 | 1.3 |53.1 | 1.1| 1200
Brown bread | -- | 43.6 | 5.4 | 1.8 |47.1 | 2.1| 1040
Bread, pastry, etc.: | | | | | | |
Graham bread | -- | 35.7 | 8.9 | 1.8| 52.1| 1.5 | 1195
Whole wheat bread | -- | 38.4 | 9.7.| 0.9| 49.7| 1.3 | 1130
Rye bread | -- | 35.7 | 9.0.| 0.6| 53.2| 1.5 | 1170
Cake | -- | 19.9 | 6.3.| 9.0| 63.3| 1.5 | 1630
Cream crackers | -- | 6.8 | 9.7.| 12.1| 69.7| 1.7 | 1925
Oyster crackers | -- | 4.8 | 11.3.| 10.5| 70.5| 2.9 | 1910
Soda crackers | -- | 5.9 | 9.8.| 9.1| 73.1| 2.1 | 1875
| | | | | | |
Sugars, etc.: | | | | | | |
| | | | | | |
Molasses | -- | -- | -- | -- | 70.0| -- | 1225
Candy[C] | -- | -- | -- | -- | 96.0| -- | 1680
Honey | -- | -- | -- | -- | 81.0| -- | 1420
Sugar, granulated | -- | -- | -- | -- |100.0| -- | 1750
Maple sirup | -- | -- | -- | -- | 71.4| -- | 1250
| | | | | | |
Vegetables:[D] | | | | | | |
Beans, dried | -- | 12.6 | 22.5.| 1.8| 59.6| 3.5 | 1520
Beans, Lima, shelled | -- | 68.5 | 7.1.| 0.7| 22.0| 1.7 | 540
Beans, string | 7.0 | 83.0 | 2.1.| 0.3| 6.9| 0.7 | 170
Beets | 20.0 | 70.0 | 1.3.| 0.1| 7.7| 0.9 | 160
Cabbage | 15.0 | 77.7 | 1.4.| 0.2| 4.8| 0.9 | 115
Celery | 20.0 | 75.6 | 0.9.| 0.1| 2.6| 0.8 | 65
Corn, green (sweet), | | | | | | |
edible portion | -- | 75.4 | 3.1 | 1.1| 19.7| 0.7 | 440
Cucumbers | 15.0 | 81.1 | 0.7.| 0.2| 2.6| 0.4 | 65
Lettuce | 15.0 | 80.5 | 1.0.| 0.2| 2.5| 0.8 | 65
Mushrooms | -- | 88.1 | 3.5 | 0.4| 6.8| 1.2 | 185
Onions | 10.0 | 78.9 | 1.4.| 0.3| 8.9| 0.5 | 190
Parsnips | 20.0 | 66.4 | 1.3.| 0.4| 10.8| 1.1 | 230
Peas _(Pisum sativum),_ | | | | | | |
dried. | -- | 9.5 | 24.6 | 1.0| 62.0| 2.9 | 1565
shelled | -- | 74.6 | 7.0 | 0.5| 16.9| 1.0 | 440
Cowpeas, dried | -- | 13.0 | 21.4.| 1.4| 60.8| 3.4 | 1505
Potatoes | 20.0 | 62.6 | 1.8.| 0.1| 14.7| 0.8 | 295
Vegetables: | | | | | | |
Rhubarb | 40.0 | 56.6 | 0.4 | 0.4 | 2.2| 0.4 | 60
Sweet potatoes | 20.0 | 55.2 | 1.4 | 0.6 | 21.9| 0.9 | 440
Spinach | -- | 92.3 | 2.1 | 0.3 | 3.2| 2.1 | 95
Squash | 50.0 | 44.2 | 0.7 | 0.2 | 4.5| 0.4 | 100
Tomatoes | -- | 94.3 | 0.9 | 0.4 | 3.9| 0.5 | 100
Turnips | 30.0 | 62.7 | 0.9 | 0.1 | 5.7| 0.6 | 120
Vegetables, canned: | | | | | | |
Baked beans | -- | 68.9 | 6.9 | 2.5 | 19.6| 2.1 | 555
Peas _(Pisum sativum),_ | | | | | | |
green | -- | 85.3 | 3.6 | 0.2 | 9.8| 1.1 | 235
Corn, green | -- | 76.1 | 2.8 | 1.2 | 19.0| 0.9 | 430
Succotash | -- | 75.9 | 3.6 | 1.0 | 18.6| 0.9 | 425
Tomatoes | -- | 94.0 | 1.2 | 0.2 | 4.0| 0.6 | 95
Fruits, berries, etc., | | | | | | |
fresh: [E] | | | | | | |
Apples | 25.0 | 63.3 | 0.3 | 0.3 | 10.8| 0.3 | 190
Bananas | 35.0 | 48.9 | 0.8 | 0.4 | 14.3| 0.6 | 260
Grapes | 25.0 | 58.0 | 1.0 | 1.2 | 14.4| 0.4 | 295
Lemons | 30.0 | 62.5 | 0.7 | 0.5 | 5.9| 0.4 | 125
Muskmelons | 50.0 | 44.8 | 0.3 | -- | 4.6| 0.3 | 80
Oranges | 27.0 | 63.4 | 0.6 | 0.1 | 8.5| 0.4 | 150
Pears | 10.0 | 76.0 | 0.5 | 0.4 | 12.7| 0.4 | 230
Persimmons, edible portion | -- | 66.1 | 0.8 | 0.7 | 31.5| 0.9 | 550
Raspberries | -- | 85.8 | 1.0 | -- | 12.6| 0.6 | 220
Strawberries | 5.0 | 85.9 | 0.9 | 0.6 | 7.0| 0.6 | 150
Watermelons | 59.4 | 37.5 | 0.2 | 0.1 | 2.7| 0.1 | 50
Fruits, dried: | | | | | | |
Apples | -- | 28.1 | 1.6 | 2.2 | 66.1| 2.0 | 1185
Apricots | -- | 29.4 | 4.7 | 1.0 | 62.5| 2.4 | 1125
Dates | 10.0 | 13.8 | 1.9 | 2.5 | 70.6| 1.2 | 1275
Fruits, dried: | | | | | | |
Rhubarb | 40.0 | 56.6 | 0.4 | 0.4 | 2.2| 0.4 | 60
| | | | | | |
Figs | -- | 18.8 | 4.3 | 0.3 | 74.2| 2.4 | 1280
Raisins | 10.0 | 13.1 | 2.3 | 3.0 | 68.5| 3.1 | 1265
Nuts: | | | | | | |
Almonds | 45.0 | 2.7 | 11.5 | 30.2 | 9.5| 1.1 | 1515
Brazil nuts | 49.6 | 2.6 | 8.6 | 33.7 | 3.5| 2.0 | 1485
Butternuts | 86.4 | 0.6 | 3.8 | 8.3 | 0.5| 0.4 | 385
Chestnuts, fresh | 16.0 | 37.8 | 5.2 | 4.5 | 35.4| 1.1 | 915
Chestnuts, dried | 24.0 | 4.5 | 8.1 | 5.3 | 56.4| 1.7 | 1385
Cocoanuts [F]| 48.8 | 7.2 | 2.9 | 25.9 | 14.3| 0.9 | 1295
Cocoanut, prepared | -- | 3.5 | 6.3 | 57.4 | 31.5| 1.3 | 2865
Filberts | 52.1 | 1.8 | 7.5 | 31.3 | 6.2| 1.1 | 1430
Hickory nuts | 62.2 | 1.4 | 5.8 | 25.5 | 4.3| 0.8 | 1145
Pecans, polished | 53.2 | 1.4 | 5.2 | 33.3 | 6.2| 0.7 | 1465
Peanuts | 24.5 | 6.9 | 19.5 | 29.1 | 18.5| 1.5 | 1775
Piñon _(Pinus edulis)_ | 40.6 | 2.0 | 8.7 | 36.8 | 10.2| 1.7 | 1730
Walnuts, black | 74.1 | 0.6 | 7.2 | 14.6 | 3.0| 0.5 | 730
Walnuts, English | 58.1 | 1.0 | 6.9 | 26.6 | 6.8| 0.6 | 1250
Miscellaneous: | | | | | | |
Chocolate | -- | 5.9 | 12.9 | 48.7 | 30.3| 2.2 | 5625
Cocoa, powdered | -- | 4.6 | 21.6 | 28.9 | 37.7| 7.2 | 2160
Cereal coffee, infusion | | | | | | |
(1 part boiled in | | | | | | |
20 parts water)[G] | -- | 98.2 | 0.2 | -- | 1.4| 0.2 | 30
=============================================================================
[Footnote A: Refuse, oil.]
[Footnote B: Refuse, shell.]
[Footnote C: Plain confectionery not containing nuts, fruit, or
chocolate.]
[Footnote D: Such vegetables as potatoes, squash, beets, etc., have a
certain amount of inedible material, skin, seeds, etc The amount varies
with the method of preparing the vegetables, and cannot be accurately
estimated The figures given for refuse of vegetables, fruits, etc., are
assumed to represent approximately the amount of refuse in these foods
as ordinarily prepared.]
[Footnote E: Fruits contain a certain proportion of inedible materials,
as skin, seeds, etc., which are properly classed as refuse. In some
fruits, as oranges and prunes, the amount rejected in eating is
practically the same as refuse. In others, as apples and pears, more or
less of the edible material is ordinarily rejected with the skin and
seeds and other inedible portions. The edible material which is thus
thrown away, and should properly be classed with the waste, is here
classed with the refuse. The figures for refuse here given represent, as
nearly as can be ascertained, the quantities ordinarily rejected.]
[Footnote F: Milk and shell.]
[Footnote G: The average of five analyses of cereal coffee grain is:
Water 6.2, protein 13.3, fat 3.4, carbohydrates 72.6, and ash 4.5 per
cent. Only a portion of the nutrients, however, enter into the infusion.
The average in the table represents the available nutrients in the
beverage. Infusions of genuine coffee and of tea like the above contain
practically no nutrients.]
CHAPTER XVII
DIETARY STUDIES
244. Object of Dietary Studies.--The quantity of food which different
families purchase varies between wide limits; a portion being lost
mechanically in preparation and a still larger and more variable amount
in the refuse and non-edible parts. If a record is made of all foods
purchased and the waste and non-edible portions are deducted, the
nutrients consumed by a family may be calculated by multiplying the
weight of each food by the average composition. If such calculations be
made, it will be found that in some families nearly a half pound per day
of both protein and fat is consumed by adults, while in other families
less than half of this amount is used. The object of dietary studies is
to determine the source, cost, composition, and nutritive value of the
foods consumed by different families; they also enable comparisons to be
made of the amounts of nutrients purchased. Extensive dietary studies
have been made by the United States Department of Agriculture, and the
results have been published in various bulletins.[76]
245. Wide and Narrow Rations.--When the amount of carbohydrates in a
ration is small in comparison with the protein, it is called a narrow
ration, while a wide ration is one in which the carbohydrates are much
in excess of the protein. When a ration contains 0.40 of a pound of
protein, 0.40 of a pound of fat, and 1 pound of carbohydrates, it has a
nutritive ratio of 1 to 4.8 and is a narrow ration. To calculate the
nutritive ratio, the fat is multiplied by 2-1/4, the product added to
the carbohydrates, and this sum divided by the protein. It is not
possible to designate accurately the amount of protein and other
nutrients that should be in the daily ration of all persons, because the
needs of the body vary so with different individuals. Hard and fast
rules governing the amounts of nutrients to be consumed cannot as yet be
formulated, as our knowledge of the subject is too limited. It is known
that both excessive and scant amounts are alike injurious. While the
appetite may indicate either hunger or satiety, it alone cannot always
be relied upon as a safe guide for determining the amount and kind of
food to consume, although the demands of appetite should not be
disregarded until it has been demonstrated beyond a doubt that it is not
voicing the needs of nature. There has been a tendency which perhaps was
a survival of the Puritanical ideas of the early days to stamp as
hurtful whatever seemed desirable and pleasant; as examples might be
cited the craving for water by fever patients, and for sugar by growing
children, which have now been proven to be normal demands of nature.
246. Dietary Standards.--As a result of a large number of dietary
studies and digestion experiments, dietary standards have been
prepared. Atwater in this country and Voit in Germany have proposed such
standards for men employed at different kinds of labor, as follows:
==========================================================================
|Protein| Fat|Carbo- | Fuel |Nutritive
| | |hydrates| Value |
---------------------------------|-------|----|-----------------|---------
| lb. | lb.| lb. |Calories| Ratio
Man with little physical exercise| 0.20 |0.20| 0.66 | 2450 | 5.5
Man with light muscular work | 0.22 |0.22| 0.77 | 2800 | 5.7
Man with moderate muscular work | 0.28 |0.28| 0.99 | 3520 | 5.8
Man with active muscular work | 0.33 |0.33| 1.10 | 4060 | 5.6
Man with hard muscular work | 0.39 |0.55| 1.43 | 5700 | 6.9
==========================================================================
In the table it will be seen that the quantity of nutrients increases
with the labor to be performed. In order to secure the necessary heat
and energy, rations for men at heavy labor contain proportionally more
fat and carbohydrates than are required for light work. All dietary
standards, however, should be regarded as tentative only. Opinions
differ greatly on different points; for example, as to the amount of
protein a ration should contain. This is a matter that can be determined
only from extended investigations under a variety of conditions, and as
yet results are too meager to formulate other than tentative standards.
Chittenden has found that the body can be sustained on very much less
protein than is called for in the standard ration.[77] The amount of
protein in the ration should be ample to sustain the body weight and
maintain a nitrogen equilibrium; that is, the income and outgo of
nitrogen from the body should be practically equal.
[Illustration: FIG. 58.--DIETARIES AND DIETARY
STANDARDS.
(From Office of Experiment Stations Bulletin.)]
"While one freely admits that health and a large measure of
muscular strength may be maintained upon a minimum supply of
protein, yet I think that a dispassionate survey of mankind will
show that races which adopt such a diet are lacking in what, for
want of a better word, one can only describe as energy." [28]
On the other hand, excessive and unnecessarily large amounts of protein
are sometimes consumed, adding greatly to the cost of the ration and
necessitating additional labor on the part of the body for its
elimination.
247. Number of Meals per Day.--Some persons advocate two meals per day
rather than three, but dietary studies show that the best results are
secured when the food is divided among three rather than two meals, and
with a two-meal system the tendency is to consume a larger total amount
of food than when three meals are eaten. It is not essential that the
food be equally divided among the three meals. Any one of them may be
lighter or more substantial as the habits and inclinations of the
individual dictate. If it is found necessary to reduce the total
quantity of food consumed, this may be done by a proportional reduction
of each of the meals, or of any one of them instead of decreasing the
number of meals per day. The occasional missing of a meal is sometimes
beneficial, in cases of digestion disorders, but the ordinary
requirements of persons in normal health who have either mental or
physical labor to perform are best met when three meals per day are
consumed, as this insures an even supply of nutrients. For persons of
sedentary habits, the kind and quantity of food at each meal must be
regulated largely by the individual from knowledge based on personal
experience.
"In the matter of diet every man must, in the last resort, be a law
unto himself; but he should draw up his dietetic code intelligently
and apply it honestly, giving due heed to the warnings which nature
is sure to address to him should he at any time transgress."[28]
If there is trouble in digesting the food, it is well to study the other
habits of life along with the food question, for it may be the
difficulty arises from some other cause, and would be remedied by more
exercise and fresh air, avoiding rush immediately after meals, more
thorough mastication, or less worry. It is a serious matter to shut off
the supply of food from a person not suffering from some disease and who
is working; as well cut off the supply of fuel from a furnace and then
expect a full amount of energy and heat. But unlike the furnace, when
the human body is deprived of needed nutrients it preys upon itself and
uses up its reserve that should be drawn upon only in cases of illness
or extreme nervous strain. Some persons live in such a way as to never
have any reserve of strength and energy to call upon but use up each day
all the body can produce and so become physical bankrupts when they
should be in their prime. Food is required for the production of nerve
energy as well as physical energy.[78]
248. Mixed Dietary Desirable.--Experiments in the feeding of farm
animals show that the best results come from the combination of a number
of foods to form a mixed ration, rather than from the use of one food
alone,[79] for in this way the work of digestion is more evenly
distributed, and a higher degree of efficiency is secured from the foods
consumed. The same is true in human feeding; the best results are
secured from a mixed diet. Ordinarily, about two fifths of the nutrients
of a ration are derived from animal and three fifths from vegetable
sources.
249. Animal and Vegetable Foods; Economy of Production.--Animal foods
can never compete in cheapness of the nutrients with cereals and
vegetables, as it takes six to eight pounds or more of a cereal,
together with forage crops, to make a pound of meat. Hence the returns
in food value are very much larger from the direct use of the cereals as
human food, than from the feeding of cereals to cattle and the use of
the meat. As the population of a country increases, and foods
necessarily become more expensive, cereals are destined to replace
animal foods to a great extent, solely as a matter of economy.
250. Food Habits.--Long-established dietary habits and customs are not
easily changed, and when the body becomes accustomed to certain foods,
substitution of others, although equally valuable, may fail to give
satisfactory results. For example, immigrants from southern Europe
demand foods with which they are familiar, as macaroni, olive oil, and
certain kinds of cheese, foods which are generally imported and more
expensive than the staples produced in this country,[80] and when they
are compelled to live on other foods, even though they have as many
nutrients, they complain of being underfed. Previously acquired food
habits appear to affect materially the process of digestion and
assimilation. Sudden and pronounced change in the feeding of farm
animals is attended with unsatisfactory results, and whenever changes
are made in the food of either humans or animals they should be gradual
rather than radical.
251. Underfed Families.--As the purchasing of food is often done by
inexperienced persons, palatability rather than nutritive value is made
the basis of choice. Dietary studies show that because of lack of
knowledge of the nutritive value of foods, whole families are often
underfed. Particularly is this true where the means for purchasing foods
are limited. In dietary studies among poor families in New York
City,[81] the United States Department of Agriculture notes: "It is
quite evident that what is needed among these families more than
anything else is instruction in the way to make the little they have go
the farthest." Some classes of the rich too are equally liable to be
underfed, as they are more prone to food notions and are able to indulge
them. Among the children of the rich are found some as poorly nourished
as among the poor.
252. Cheap and Expensive Foods.--Among the more expensive items of a
ration are meats, butter, and canned fruits. The difference in
composition and nutritive value between various cuts of meat is small,
being largely physical, and affecting taste and flavor rather than
nutritive value. Expensive cuts of meat, high-priced breakfast cereals,
tropical fruits and foods which impart special flavors, add little in
the way of nutritive value to the ration, but greatly enhance the cost
of living. Ordinarily the cheapest foods are corn meal, wheat flour and
bread, milk, beans, cheese, sugar, and potatoes.[7] The amount of animal
and vegetable foods to combine with these to form a balanced ration may
be governed largely by personal preference or cost, as there is little
difference in nutritive value. The selection of foods on the basis of
cost and nutritive value is discussed in Chapter XVI.
253. Food Notions.--Many erroneous ideas exist as to the nutritive
value of foods, and often wholesome and valuable foods are discriminated
against because of prejudice. Skim milk is usually regarded as
containing little if any nourishing material, when in reality it has a
high protein content, and can be added to other foods to increase their
nutritive value. The less expensive cuts of meat contain more total
nutrients than many of the more expensive ones. Beef extracts have been
erroneously said to contain more nutrients than beef,[51] and mushrooms
to be equal in value of beefsteak; chemical analyses fail to confirm
either statement. The banana also has been overestimated as to food
value, and while it contains more nutrients than many fruits, it is not
the equal of cereals, as has been claimed.[82] Cocoa, although a
valuable beverage, adds but little in the way of nutrients to a ration
unless it is made with milk. The value of a food should be based upon
its composition as determined by chemical analysis, its digestibility as
founded upon digestion experiments, and its palatability and mechanical
structure. Food notions have, in many instances, been the cause of
banishing from the dietary wholesome and nutritious foods, of greatly
increasing the cost of living, as well as of promulgating incorrect
ideas in regard to foods, so that individuals and in some cases entire
families have suffered from improper or insufficient food.
254. Dietary of Two Families Compared.--A dietary study often reveals
ways in which it is possible to improve the ration in kinds and amounts
of food, and sometimes at less expense. The following dietaries of two
families for the same period show that one family expends over twice as
much in the purchase of foods as the other family, and yet the one whose
food costs the less actually secures the larger amount of nutritive
material and is better fed than the family where more money is expended
for food.[13]
FOOD CONSUMED, ONE WEEK
FAMILY No. 1
20 loaves of bread $1.00
10 to 12 lb. loin steak, or meat of similar cost 2.00
20 to 25 lb. rib roast, or similar meat 4.40
4 lb. high-priced cereal breakfast food, 20 ct. 0.80
Cake and pastry purchased 3.00
8 lb. butter, 30 ct. 2.40
Tea, coffee, spices, etc 0.75
Mushrooms 0.75
Celery 1.00
Oranges 2.00
Potatoes 0.25
Miscellaneous canned goods 2.00
Milk 0.50
Miscellaneous foods 2.00
3 doz. eggs 0.60
------
$23.45
FAMILY No. 2
15 lb. flour, bread home-made (skim milk used) $0.45
Yeast, shortening and skim milk 0.10
10 lb. steak (round. Hamburger and some loin) 1.50
10 lb. other meats, boiling pieces, rump roast, etc. 1.00
5 lb. cheese, 16 cents 0.80
5 lb. oatmeal (bulk) 0.15
5 lb. beans 0.25
Home-made cake and pastry 1.00
6 lb. butter, 30 ct. 1.80
3 lb. home-made shortening 0.25
Tea, coffee, and spices 0.40
Apples 0.50
Prunes 0.25
Potatoes 0.25
Milk 1.00
Miscellaneous foods 1.00
3 doz. eggs 0.60
------
$11.30
[Illustration: FIG. 59.--COST AND NUTRITIVE VALUE OF RATIONS.]
In comparing the foods used by the two families, it will be observed
that family No. 1 purchased their bread at the bakery at a cost of $
1.00, while the bread of family No. 2 was home-made, skim milk being
used in its preparation, the flour, milk, yeast, and shortening costing
about 55 cents. Family No. 1 consumed 10 pounds of expensive steaks,
family No. 2 consumed the same number of pounds, a portion being cheaper
cuts. Instead of the 20 pounds of roast or similar beef used by family
No. 1, only one half as much and cheaper cuts as boiling pieces, stew,
rump roast, etc., were used by family No. 2; 5 pounds of beans and 5
pounds of cheese taking the place of some of the meat. Family No. 1
consumed 4 pounds of high-priced cereal breakfast foods, supposing they
contained a larger amount of nutrients than were actually present. In
place of the 4 pounds of high-priced cereal breakfast foods of family
No. 1, family No. 2 used 5 pounds of oatmeal purchased in bulk. Family
No. 1 bought their cake and pastry for $3.00, while those of family No.
2 were home made and cost $1.00. Family No. 2 used 2 pounds less butter
per week because of the preparation and use of home-made shortening from
beef suet and milk. They also purchased a smaller amount of tea, coffee,
and spices than family No. 1. Family No. 2 consumed a larger quantity of
less expensive fruits and vegetables than family No. 1, who ate 75
cents' worth of mushrooms with the idea that they contained as much
protein as meat, but analyses show that mushrooms contain no more
nutrients than potatoes and similar vegetables. In place of the celery
and oranges, apples and prunes were used by family No. 2. The same
amount of potatoes was used by each. Fifty cents was spent for milk by
family No. 1 and $1.00 by family No. 2. The total amount expended for
food by family No. 1 was $23.45, while family No. 2 purchased a greater
variety of foods for $11.30, as well as foods containing more nutrients.
The approximate amounts of nutrients in the foods purchased by the two
families are given in the following table, from which it will be
observed that family No. 2 obtained a much larger amount of total
nutrients and was better fed at considerably less expense than family
No. 1.
NUTRIENTS IN FOODS CONSUMED.--FAMILY NO. 1
=============================================
|PROTEIN| FAT |CARBOHYDRATES
| LB. | LB. | LB.
-------------------------|-----|-------------
20 lb. bread | 1.98 | 0.28| 11.42
10 lb. loin steak| 1.59 | 1.76| --
20 lb. rib roast | 2.68 | 4.26| --
4 lb. cereals | 0.42 | 0.06| 2.75
8 lb. butter | 0.04 | 6.80| --
25 lb. potatoes | 0.45 | 0.03| 3.83
20 lb. milk | 0.70 | 0.80| 1.00
|-------|-----|-------------
| 7.86 |13.99| 19.00
=============================================
FAMILY NO. 2
=====================================================
|PROTEIN| FAT |CARBOHYDRATES
| LB. | LB. | LB.
-------------------------|-------|-----|-------------
15 lb. flour | 1.89 | 0.12| 11.15
5 lb. skim milk | 0.16 | 0.01| 0.26
10 lb. round steak | 1.81 | 1.26| --
10 lb. beef | 1.32 | 2.02| --
5 lb. cheese | 1.40 | 1.75| --
5 lb. oatmeal | 0.78 | 0.36| 3.40
6 lb. butter | 0.03 | 5.10| --
3 lb. shortening | -- | 2.55| --
3 lb. prunes | 0.03 | -- | 0.60
25 lb. apples | 0.12 | -- | 2.50
25 lb. potatoes | 0.45 | 0.03| 3.83
40 lb. milk | 1.44 | 1.60| 1.90
5 lb. beans | 1.12 | -- | 3.00
-------------------------|-------|-----|------------------
| 10.55 |14.80| 26.64
-------------------------|-------|-----|------------------
Difference in nutrients |
in favor of family No. 2,|
consuming the cheaper |2.69 0.81 7.64
combination of foods |
=====================================================
255. Food in its Relation to Mental and Physical Vigor.--When the body
is not properly supplied with food, the best results in the form of
productive work cannot be secured. There is a close relationship between
the nature of the food consumed and mental activity, also ability to
satisfactorily perform physical labor. "The productive power of the
individual as well as of the nation depends doubtless upon many factors
other than food, such as race, climate, habit, etc., but there is no
gainsaying the fact that diet has also a profound and direct influence
upon it."[83]
If the body is diseased, it cannot make the right uses of the food, and
often the food is blamed when the trouble is due primarily to other
causes. The fact that a diseased digestive tract is unable to utilize
some foods is no valid reason why these foods should be discarded in the
dietary of persons in normal health, particularly when the food is in no
way responsible for the disease.
Some diseases are most prevalent in the case of a restricted diet. A
change in the dietary of the Japanese navy greatly improved the health
of the sailors.
"The prevalence of kakke or beriberi in the navy turned the
attention of many medical specialists toward the problem of
nutrition.... It was generally believed that there was some very
close connection between the disease and the rice diet.... One
outcome of these investigations was the passage of the food supply
act of the navy in 1884. The ration provided in accordance with
this act was sufficient to furnish an abundance of protein and
energy.... Following the change of ration in 1884, the prevalence
of the disease was very materially diminished, and at the end of
three years cases of kakke were practically unknown among the
marines."[83]
256. Dietary Studies in Public Institutions.--Dietary studies in
public institutions, as prisons, and asylums for the insane, show that
it is possible to secure greater variety of food containing a larger
amount of nutrients, and even at a reduction in cost.[84] In such
institutions it is important that the food should be not only ample in
amount, but wholesome and nutritious, as many of the inmates respond
both physically and mentally to an improved diet. For humanitarian as
well as economic reasons institutional dietetics should more generally
be placed under the supervision of skilled dietists.
CHAPTER XVIII
RATIONAL FEEDING OF MAN
257. Object.--Rational feeding of man has for its object the
regulation of the food supply in accord with the demands of the body. It
is based upon the same principles as the rational feeding of animals; in
each, the best results in the way of health, amount of labor performed,
and economy are secured when the body receives nutrients sufficient for
the production of heat and energy and for the repair of worn-out
tissues. Rational feeding is simply regulation of the food, both as to
kind and amount, to meet the needs of the body.[72]
258. Standard Rations.--In human feeding, as in animal feeding, it is
not possible to lay down hard and fast rules as to the quantity of
nutrients required for a standard ration.[85] As stated in the chapter
on Dietary Studies, such standards have been proposed, but they are to
be considered as tentative rather than absolute, for the amount of food
required by different persons must necessarily vary with the
individuality. While it is impossible to establish absolute standards,
any large variation from the provisional standards usually results in
lessened ability to accomplish work, ill health, or increased expense.
259. Amounts of Food Consumed.--The approximate amounts of some food
articles consumed per day are as follows:
===================================
| RANGE | APPROXIMATE
| |AMOUNT IN LBS.
--------|--------------------------
Bread |6 to 14 oz.| 0.50
Butter |2 to 5 oz.| 0.12
Potatoes|8 to 16 oz.| 0.75
Cheese |1 to 4 oz.| 0.12
Beans |1 to 4 oz.| 0.12
Milk |8 to 32 oz.| --
Sugar |2 to 5 oz.| 0.20
Meats |4 to 12 oz.| 0.25
Oatmeal |1 to 4 oz.| 0.12
===================================
In the calculation of rations it is desirable that the amount of any
food article should not exceed that designated, unless for some special
reason it has been found the food can consistently be increased. The
amount of nutrients given in dietary standards is for one day, and the
nutrients may be divided among the three meals as desired. It is to be
noted that, ordinarily, the foods which supply carbohydrates are flour,
corn meal, cereal products, potatoes, beans, sugar, and milk; those
which supply fat are milk, butter, lard, and meats; and those which
supply protein in liberal amounts are beans, cheese, meats, oatmeal,
cereals, bread, and milk.
260. Average Composition of Foods.--The amounts of nutrients in foods
are determined from the average composition of the foods. These figures
for average composition are based upon analyses of a large number of
samples of food materials.[7] In individual cases it will be found that
foods may vary from the standards given; as for example, milk may
contain from 2.5 to 5 per cent of fat, while the protein and fat of
meats vary appreciably from the figures given for average composition.
With the cereals and vegetable foods, variations from the standards are
small. In the table, the composition of the food as purchased represents
all of the nutrients in the food, including those in the refuse,
trimmings, or waste, while the figures for the edible portion represent
the nutrients in the food after deducting what is lost as refuse. In
making calculations, the student should use the figures given for the
foods as purchased, unless the weights are of the edible portion only.
The figures in the table are on the basis of percentage amounts, or
nutrients in 100 pounds of food. By moving the decimal point two places
to the left, the figures will represent the nutrients in one pound, and
if this is multiplied by the number of pounds or fraction of a pound
used, the quantity of nutrients is secured. For example, suppose bread
contains 9.5 per cent of protein and 56 per cent of carbohydrates, 1
pound would contain 0.095 pound of protein, 0.56 pound of
carbohydrates; and 0.5 of a pound would contain approximately 0.05 pound
of protein and 0.28 pound of carbohydrates. In calculating rations, it
is not necessary to carry the figures to the third decimal place.
[Illustration: FIG. 60.--FOOD ARTICLES FOR A HUMAN RATION.]
261. Example of a Ration.--Suppose it is desired to calculate a ration
for a man at light muscular work. First, note the requirements in the
way of nutrients in the table "Dietary Standards," Section 246. Such a
ration should supply approximately 0.22 pound each of protein and fat,
and 0.77 pound of carbohydrates, and should yield 2800 calories. A trial
ration is made by combining the following:
==========================================================
| Pound
Bread | 0.50
Butter | 0.12
Potatoes | 0.75
Milk | 1.00
Sugar | 0.12
Beef | 0.25
Ham | 0.20
Oatmeal | 0.12
Eggs | 0.25
==========================================================
The quantities of nutrients in these food materials are approximately as
follows:
RATION FOR MAN AT MODERATE WORK
===================================================================
| | PROTEIN | FAT | C.H. |
| LB. | LB. | LB. | LB. | CALORIES
-------------------------+------+---------+------+------+----------
Bread | 0.50 | 0.05 | 0.01 | 0.29 | 653
Butter | 0.12 | -- | 0.10 | -- | 432
Potato | 0.75 | 0.01 | -- | 0.12 | 244
Milk | 1.00 | 0.04 | 0.04 | 0.05 | 323
Sugar | 0.12 | -- | -- | 0.12 | 192
Beef (round) | 0.25 | 0.05 | 0.03 | -- | 218
Ham | 0.20 | 0.03 | 0.07 | -- | 331
Oatmeal | 0.12 | 0.02 | 0.01 | 0.08 | 223
Eggs | 0.25 | 0.03 | 0.03 | -- | 164
Squash | 0.20 | -- | -- | 0.01 | 25
|------+---------+------+------+----------
| | 0.23 | 0.29 | 0.67 | 2805
===================================================================
It is to be noted that this ration contains approximately the amount of
protein called for in the standard ration, while the fat is slightly
more and the carbohydrates are less. The food value of the ration is
practically that called for in the standard. This ration is sufficiently
near the standard to supply the nutrient requirements of a man at light
muscular work. To supply palatability, some fruit and vegetables should
be added to the ration. These will contribute but little to the nutrient
content, but are necessary in order to secure health and the best
returns from the other foods, and as previously stated, they are not to
be estimated entirely upon the basis of nutrient content. A number of
food articles could be substituted in this ration, if desired, either in
the interests of economy, palatability, or personal preference.
262. Requisites of a Balanced Ration.--Reasonable combinations of
foods should be made to form balanced rations.[2] A number of foods slow
of digestion, or which require a large amount of intestinal work, should
not be combined; neither should foods which are easily digested and
which leave but little indigestible residue. After a ration has been
calculated and found to contain the requisite amount of nutrients, it
should be critically examined to see whether or not it fulfills the
following requirements:
1. Economy and adaptability to the work required.
2. Necessary bulk or volume.
3. Desired physiological influence of the foods upon the digestive
tract, whether constipating or laxative in character.
4. Ease of digestion.
5. Effect upon health. It is recognized that there are foods
wholesome and nutritious, that cannot be used by some persons,
while with others the same foods can be consumed with impunity.
As explained in the chapter on Dietary Studies, the nutrients should be
supplied from a number of foods rather than from a few, because it is
believed the various nutrients, particularly the proteins, are not
absolutely identical from all sources, or equal in nutritive value.
EXAMPLES
1. Calculate a ration for a man with little physical exercise.
2. Calculate a ration for a man at hard muscular labor, and give the
approximate cost of the ration.
3. Calculate the amounts of food and the nutrient requirements for a
family of seven for 10 days; five of the family to consume 0.8 as much
as an adult. Calculate the cost of the food; then calculate on the same
basis the probable cost of food for one year, adding 20 per cent for
fluctuation in market price and additional foods not included in the
list.
4. Weigh out the food articles used in problem No. 2, and apportion them
among three meals.
CHAPTER XIX
WATER
263. Importance.--Water is one of the most essential food materials.
It enters into the composition of the body, and without it the nutrients
of foods would be unavailable, and life could not be sustained. Water
unites chemically with various elements to form plant tissue and
supplies hydrogen and oxygen for the production of organic compounds
within the leaves of plants. In the animal economy it is not definitely
known whether or not water furnishes any of the elements of which the
tissues are composed, as the food contains liberal amounts of hydrogen
and oxygen; it is necessary mainly as the vehicle for distributing
nutrients in suspension and solution, and as a medium in which chemical,
physical, and physiological changes essential to life processes take
place. From a sanitary point of view, the condition of the water supply
is of great importance, as impure water seriously affects the health of
the consumer.[87]
264. Impurities in Water.--Waters are impure because of: (1) excessive
amounts of alkaline salts and other mineral compounds; (2) decaying
animal and vegetable matters which act chemically as poisons and
irritants, and which may serve as food for the development of
objectionable bacterial bodies; and (3) injurious bacteria. The most
common forms of impurities are excess of organic matter and bacterial
contamination. The sanitary condition of water is greatly influenced by
the character of the soil through which it flows and the extent to which
it has been polluted by surface drainage.[88]
[Illustration: FIG. 61.--DIRT AND IMPURITIES IN A SURFACE WELL WATER.]
265. Mineral Impurities.--- The mineral impurities of water are mainly
soluble alkaline and similar compounds dissolved by the water in passing
through various layers of soil and rock. When water contains a large
amount of sodium chloride, sodium sulphate or carbonate, or other
alkaline salts, it is termed an "alkali water." Where water passes
through soil that has been largely formed from the decay of rocks
containing alkaline minerals, the water dissolves some of these minerals
and becomes alkaline. The kind of alkali determines the character of the
water; in some cases it is sodium carbonate, which is particularly
objectionable. The continued use of strong alkali water causes digestion
disorders, because of the irritating action upon the digestive tract.
Hard waters are due to the presence of lime compounds. In regions where
limestone predominates, the carbon dioxid in water acts as a solvent,
producing hard waters. Waters that are hard on account of the presence
of calcium carbonate give a deposit when boiled, due to liberation of
the carbon dioxid which is the material that renders the lime soluble.
Calcium sulphate, or gypsum, on the other hand, imparts permanent
hardness. There is no deposit when such waters are boiled. A large
number of minerals are found in various waters, often sufficient in
amount to impart physiological properties. Water that is highly charged
with mineral matter is difficult to improve sufficiently for household
purposes. About the only way is by distillation.[89]
266. Organic Impurities.--Water that flows over the surface of the
ground comes in contact with animal and vegetable material in various
stages of decay, and as a result some is dissolved and some is
mechanically carried along by the water. After becoming soluble, the
organic matter undergoes further chemical changes, as oxidation and
nitrification caused by bacteria. If the organic matter contain a large
amount of nitrogenous material, particularly of proteid origin, a series
of chemical changes induced by bacterial action takes place, resulting
in the production of nitrites. The nitrifying organisms first produce
nitrous acid products (nitrites), and in the further development of the
nitrifying process these are changed to nitrates. The ammonia formed as
the result of the decomposition of nitrogenous organic matter readily
undergoes nitrification changes. Nitrates and nitrites alone are not
injurious in water, but they are usually associated with objectionable
bacteria and generally indicate previous contamination.[90]
267. Interpretation of a Water Analysis.--"Total solid matter"
represents all the mineral, vegetable, and animal matter which a water
contains. It is the residue obtained by evaporating the water to dryness
at a temperature of 212° F. Average drinking water contains from 20 to
90 grains per gallon of solid matter. "Free ammonia" is that formed as a
result of the decomposition of animal or vegetable matter containing
nitrogen. Water of high purity usually contains less than 0.07 parts
per million of free ammonia. "Albuminoid ammonia" is derived from the
partially decomposed animal or vegetable material in water. The greater
the amount of nitrogenous organic impurities, the higher the albuminoid
ammonia. A good drinking water ought not to contain more than 0.10 part
per million of albuminoid ammonia. An abnormal quantity of chlorine
indicates surface drainage or sewage contamination, or an excess of
alkaline matter, as common salt. Nitrites should not be present, as they
are generally associated with matter not completely oxidized. Nitrites
are usually considered more objectionable than nitrates; both are
innocuous unless associated with disease-producing nitroörganisms.
268. Natural Purification of Water.--River waters are sometimes dark
colored because of large amounts of dissolved organic matter, but in
contact with the sun and air they gradually undergo natural purification
and the organic matter is oxidized. However, absolute reliance cannot be
placed upon natural purification of a bad water, as the objectionable
organisms often have great resistive power. There is no perfectly pure
water except that prepared in the chemical laboratory by distillation.
All natural waters come in contact with the soil and air, and
necessarily contain impurities proportional to the extent of their
contamination.
269. Water in Relation to Health.--There are many diseases, of which
typhoid fever is a type, that are distinctly water-born. The typhoid
bacilli, present in countless numbers in the feces of persons suffering
or convalescent from typhoid fever, find their way into streams, lakes,
and wells.[91] They retain their vitality, and when they enter the
digestive tract of an individual, rapidly increase in numbers. Numerous
disastrous outbreaks of typhoid fever have been traced to contamination
of water. Coupled with the sanitary improvement of a city's water
supply, there is diminution of typhoid fever cases, and a noticeable
lowering of the death rate. Many cities and villages are dependent for
their water upon rivers and lakes into which surface drainage finds its
way, with all contaminating substances. Mechanical sedimentation and
filtration greatly improve waters of this class, but do not necessarily
render them entirely pure. Compounds of iron and aluminium are sometimes
added in small amounts, under chemical supervision, to such waters to
precipitate the organic impurities. Spring waters are not entirely above
suspicion, as oftentimes the soil through which they flow is highly
polluted. All water of doubtful purity should be boiled, and there are
but few natural waters of undoubted purity. There is no such thing as
absolutely pure water in a state of nature. The mountain streams perhaps
approach nearest to it where there are no humans to pollute the banks;
but then there are always the beasts and birds, and they, too, are
subject to disease. There are very few waters that at some time of the
year and under some conditions are not contaminated with
disease-producing organisms. No matter how carefully guarded are the
banks of lakes furnishing the water supply of cities, more or less
objectionable matter will get in. In seasons of heavy rains, large
amounts of surface water enter the lakes, carrying along the filth
gathered from many acres of land drained by the streams entering the
lakes. Some of the most serious outbreaks of typhoid fever have come
from temporary contamination of ordinarily fairly good drinking water.
In general, too little attention is given to the purity of drinking
water. It is just as important that water should be boiled as that food
should be cooked. One of the objects of cooking is to destroy the
injurious bacteria, and they are frequently more numerous in the
drinking water than in the food.
The argument is sometimes advanced that the mineral matter present in
water is needed for the construction of the bone and other tissues of
the body, and that distilled water fails to supply the necessary mineral
matter. This is an erroneous assumption, as the mineral matter in the
food is more than sufficient for this purpose. When water is highly
charged with mineral salts, additional work for their elimination is
called for on the part of the organs of excretion, particularly the
kidneys; and furthermore, water nearly saturated with minerals cannot
exert its full solvent action.
In discussing the immediate benefits resulting from improvement of
water, Fuertes says:[92]
"Immediately after the change to the 'four mile intake' at Chicago
in 1893, there was a great reduction in typhoid. Lawrence, Mass.,
showed a great improvement with the setting of the filters in
operation in September, 1893; fully half of the deaths in 1894 were
among persons known to have used the unfiltered canal water. The
conclusion is warranted that for the efficient control of the death
rate from typhoid fever it is necessary to have efficient sewerage
and drainage, proper methods of living, and pure water. The reason
why our large cities, which are all provided with sewerage, have
such high death rates is therefore without doubt their continuance
of the filthy practice of supplying drinking water which carries in
solution and suspension the washings from farms, from the streets,
from privies, from pigpens, and the sewage of cities.... And also
we should recognize the importance of flies and other winged
insects and birds which feed on offal as carriers of bacteria of
specific diseases from points of infection to the watersheds, and
the consequent washing of newly infected matter into our drinking
water by rains."
There is a very close relationship between the surface water and that of
shallow wells. A shallow well is simply a reservoir for surface water
accumulations. It is stated that, when an improved system of drainage
was introduced into a part of London, many of the shallow wells became
dry, indicating the source from which they received their supply. Direct
subterranean connection between cesspools and wells is often traced in
the following way: A small amount of lithium, which gives a distinct
flame reaction, and a minute trace of which can be detected with the
spectroscope, is placed in the cesspool, and after a short time a
lithium reaction is secured from the well water.
Rain water is relied upon in some localities for drinking purposes. That
collected in cities and in the vicinity of barns and dwellings contains
appreciable amounts of organic impurities. The brown color is due to the
impurities, ammonium carbonate being one of these. There are also traces
of nitrates and nitrites obtained from the air. When used for drinking,
rain water should be boiled.
270. Improvement of Waters.--Waters are improved by: (1) boiling,
which destroys the disease-producing organisms; (2) filtration, which
removes the materials mechanically suspended in the water; and (3)
distillation, which eliminates the impurities in suspension and
solution, as well as destroys all germ life.
271. Boiling Water.--In order to destroy the bacteria that may be in
drinking water, it is not sufficient to heat the water or merely let it
come to a boil. It has been found that if water is only partially
sterilized and then cooled in the open air, the bacteria develop more
rapidly than if the water had not been heated at all. It should boil
vigorously five to ten minutes; cholera and typhoid bacteria succumb in
five minutes or less. Care should be taken in cooling that the water is
not exposed to dust particles from the air nor placed in open vessels in
a dirty refrigerator. It should be kept in perfectly clean,
tight-stoppered bottles. These bottles should be frequently scalded.
Great reliance may be placed upon this method of water purification when
properly carried out.
272. Filtration.--Among the most efficient forms of water filters are
the Berkefeld and Pasteur. The Pasteur filter is made of unglazed
porcelain, and the Berkefeld of fine infusorial earth (finely divided
SiO_{2}). Both are porous and allow a moderately rapid flow of water.
The flow from the Berkefeld filter is more rapid than from the Pasteur.
The mechanical impurities of the water are deposited upon the filtering
surface, due to the attraction which the material has for particles in
suspension. These particles usually are the sources of contamination and
carry bacteria. When first used, filters are satisfactory, but unless
carefully looked after they soon lose their ability to remove germs from
the water and may increase the impurity by accumulation. Small faucet
filters are made of porous stone, asbestos, charcoal, etc. Many of them
are of no value whatever or are even worse than valueless. Filters
should be frequently cleansed in boiling water or in steam under
pressure. Unless this is done, the filters may become incubators for
bacteria.
[Illustration: FIG. 62.--PASTEUR WATER FILTERS.]
273. Distillation.--When an unquestionably pure water supply is
desired, distillation should be resorted to. There are many forms of
stills for domestic use which are easily manipulated and produce
distilled water economically.[93] The mineral matter of water is in no
way essential for any functional purpose, and hence its removal through
distillation is not detrimental.
[Illustration: FIG. 63.--WATER STILL.]
274. Chemical Purification.--Purification of water by the use of
chemicals should not be attempted in the household or by inexperienced
persons. When done under supervision of a chemist or bacteriologist, it
may be of great value to a community. Turneaure and Russell,[94] in
discussing the purification of water by addition of chemicals, state:
"There are a considerable number of chemical substances that may be
added to water in order to purify it by carrying down the suspended
matter as well as bacteria, by sedimentation. Such a process of
purification is to be seen in the addition of alum, sulphate of
iron, and calcium hydrate to water. Methods of this character are
directly dependent upon the flocculating action of the chemical
added, and the removal of the bacteria is accomplished by
subsidence."
275. Ice.--The purity of the ice supply is also of much importance.
While freezing reduces the number of organisms and lessens their
vitality, it does not make an impure water absolutely wholesome. The
way, too, in which ice is often handled and stored subjects it to
contamination, and foods which are placed in direct contact with it
mechanically absorb the impurities which it contains. For cooling water,
ice should be placed around rather than in it. Diseases have frequently
been traced to impure ice. The only absolutely pure ice is that made
from distilled water.
276. Mineral Waters.--When water is charged with carbonic acid gas
under pressure, carbonated water results, and when minerals, as salts of
sodium, potassium, or lithium, are added, artificial mineral waters are
produced. Natural mineral waters are placed on the market to some
extent, but most mineral waters are artificial products and they are
sometimes prepared from water of low sanitary character. Mineral waters
should not be used extensively except under medical direction, as many
have pronounced medicinal properties. Some of the constituents are
bicarbonates of sodium, potassium, and lithium; sulphates of magnesium
(Epsom salts) and calcium; and chloride of sodium. The sweetened mineral
waters, as lemonade, orangeade, ginger ale, and beer, contain sugar and
organic acids, as citric and tartaric, and are flavored with natural or
artificial products. Most of them are prepared without either fruit or
ginger. Natural mineral waters used under the direction of a physician
are often beneficial in cases of chronic digestion disorders or other
diseases.
277. Materials for Softening Water.--The materials most commonly used
for softening water are sodium carbonate (washing soda), borax, ammonia,
ammonium carbonate, potash, and soda lye. Waters that are very hard with
limestone should have a small amount of washing soda added to them. Two
ounces for a large tub of water is the most that should be used, and it
should first be dissolved in a little water. If too much soda is used,
it is injurious, as only a certain amount can be utilized for softening
the water, and the excess simply injures the hands and fabric. When hard
limewater is boiled and a very little soda lye added, a precipitate of
carbonate of lime is formed, and then if the water is strained, it is
greatly improved for washing purposes. Borax is valuable for making some
hard waters soft. It is not as strong in its action as is sodium
carbonate. For the hardest water 1/4 pound of borax to a large tubful
may be used; most waters, however, do not need so much. Ammonia is one
of the most useful reagents for softening water. It is better than
washing soda and borax, because the ammonia is volatile and does not
leave any residue to act on the clothes, thus causing injury. For
bathing purposes, the water should be softened with ammonia, in
preference to any other material. Ammonia should not be poured directly
into hot water; it should be added to the water while cold, or to a
small quantity of cold water, and then to the warm water, as this
prevents the ammonia from vaporizing too readily. Ammonia produces the
same effect as potash or soda lye, without leaving a residue in the
garments washed. It is especially valuable in washing woolen goods or
materials liable to shrink. Waters which are hard with alum salts are
greatly benefited by the addition of ammonia. A little in such a water
will cause a precipitate to form, and when the water is strained it is
in good condition for cleaning purposes. Ammonium carbonate is used to
some extent as a softening and cleaning agent, and is valuable, as there
is no injurious effect upon clothing, because it readily volatilizes.
Caustic potash and caustic soda are sometimes employed for softening
water, but they are very active and are not adapted to washing colored
or delicate fabrics. They may be used for very heavy and coarse articles
that are greasy,--not more than a gram in a gallon of water. Bleaching
powder is not generally a safe material for cleansing purposes, as it
weakens the texture of clothing. After a contagious disease, articles
may be soaked in water containing a little bleaching powder and a few
drops of carbolic acid, followed by thorough rinsing and bleaching in
the sun. But as a rule formaline is preferable for disinfecting
clothing. It can be used at the rate of about one pound to 100 gallons
of water. Bleaching powder, caustic potash or soda, and strong soap are
not suitable for cleaning woodwork, because of the action of the alkali
on paint and wood; they roughen the surface and discolor the paint.
Waters vary so in composition, that a material suitable for softening
one may not prove to be the best for softening another. The special kind
must be determined largely by trial, and it should be the aim to use as
little as possible. When carbolic acid, formaline, bleaching powder, and
caustic soda are used, the hands should be protected and the clothes
should be well rinsed.
[Illustration: FIG. 64.--TYPHOID BACILLI.]
278. Economic Value of a Pure Water Supply.--From a financial point of
view, the money spent in securing pure water is one of the best
investments a community can make. Statisticians estimate the death of an
adult results in a loss to the state of from $1000 to $5000; and to the
losses sustained by death must be added those incurred by sickness and
by lessened quality and quantity of work through impaired
vitality,--all caused by using poor drinking water. Wherever plants have
been installed for improving the sanitary condition of the water supply,
the death rate has been lowered and the returns to the community have
been far greater than the cost of the plant. Impure water is the most
expensive food that can be consumed.
CHAPTER XX
FOOD AS AFFECTED BY HOUSEHOLD SANITATION AND STORAGE
279. Injurious Compounds in Foods.--An ordinary chemical analysis of a
food determines only the nutrients, as protein, carbohydrates, and fats;
and unless there is reason to believe the food contains injurious
substances no special tests for these are made. There are a number of
poisonous compounds that foods may contain, and many of them can but
imperfectly be determined by chemical analysis. Numerous organic
compounds are produced in foods as the result of the workings of
microörganisms; some of these are poisonous, while others impart only
special characteristics, as taste and odor. The poisonous bacteria
finding their way into food produce organic compounds of a toxic
character; and hence it is that the sanitary condition of a food, as
influenced by preparation and storage, is often of more vital importance
than the nutrient content.[95]
[Illustration: FIG. 65.--TUBERCULOSIS BACILLI. (After CONN.)
Often present in dust particles and contaminated foods.]
280. Sources of Contamination of Food.--As a rule, too little
attention is given to the sanitary handling and preparation of foods.
They are often exposed to impure air and to the dust and filth from
unclean streets and surroundings, and as a result they become inoculated
with bacteria, which are often the disease-producing kind. Gelatine
plates exposed by bacteriologists under the same conditions as foods
develop large numbers of injurious microörganisms. In order to avoid
contamination in the handling of food, there must be: (1) protection
from impure air and dust; (2) storage in clean, sanitary, and ventilated
storerooms and warehouses; (3) storage of perishable foods at a low
temperature so as to retard fermentation changes; and (4) workmen free
from contagious diseases in all occupations pertaining to the
preparation of foods. Ordinarily, foods should not be stored in the
paper wrappers in which they are purchased, as unclean paper is often a
source of contamination.
281. Sanitary Inspection of Food.--During recent years some state and
city boards of health have introduced sanitary inspection of foods, with
a view of preventing contamination during manufacture and
transportation, and this has done much to improve the quality and
wholesomeness. Putrid meats, fish, and vegetables are not allowed to be
sold, and foods are required to be handled and stored in a sanitary way.
Next to a pure water supply, there is no factor that so greatly
influences for good the health of a community as the sanitary condition
of the food. While the cooking of foods destroys many organisms, it
often fails to render innocuous the poisons which they produce, and
furthermore the unsound foods when cooked are not entirely wholesome,
and they have poor keeping qualities.
Often meats, vegetables, and other foods eaten uncooked, as well as the
numerous cooked foods, are exposed in dirty market places, and
accumulate large amounts of filth, and are inoculated with disease germs
by flies. Protection of food from flies is a matter of vital importance,
as they are carriers of many diseases. In the case of typhoid fever,
next to impure drinking water flies are credited with being the greatest
distributors of the disease germs.[96]
[Illustration: FIG. 66.--DIPHTHERIA BACILLI. (After CONN.)
Often present in dust particles and in food unprotected from dust.]
282. Infection from Impure Air.--The dust particles of the air contain
decayed animal and vegetable matter in which bacteria are present; these
find their way into the food when it is not carefully protected, into
the water supply, and also into the lungs and other organs of the body.
When foods are protected from the mechanical impurities which gain
access through the air, and fermentation is delayed by storage at a low
temperature, digestion disorders are greatly lessened. From a sanitary
point of view, the air of food storerooms and of living rooms should be
of equally high purity. When foods are kept in unventilated living
rooms, they become contaminated with the impurities thrown off from the
lungs in respiration, which include not only carbon dioxid, but the more
objectionable toxic organic materials.
Vegetable foods need to be stored in well-ventilated places, as the
plant cells are still alive and carrying on life functions, as the
giving off of carbon dioxid, which is akin to animal respiration; in
fact, it is plant-cell respiration. Provision should be made for the
removal of the carbon dioxid and other products, as they contaminate the
air. When vegetable tissue ceases to produce carbon dioxid, death and
decay set in, accompanied by fermentation changes.
283. Storage of Food in Cellars.--Cellars are often in a very
unsanitary condition, damp, poorly lighted, unventilated, and the air
filled with floating particles from decaying vegetables. The walls and
shelves absorb the dust and germs from the foul air and are bacterially
contaminated, and whenever a sound food is stored in such a cellar, it
readily becomes inoculated with bacteria. There is a much closer
relationship existing between the atmosphere of the cellar and that of
the house than is generally realized. An unclean cellar means
contaminated air throughout the house. When careful attention is given
to the sanitary condition of the cellar, many of the more common
diseases are greatly reduced. Cases of rheumatism have often been traced
to a damp cellar. In some localities where the cellars are unusually
unsanitary, there is in the season of spring rains, when they are
especially damp and contain the maximum of decayed vegetation, a
prevalence of what might be called "cellaritis." The symptoms differ and
the trouble is variously attributed, but the real cause is the same,
although overlooked, for, unfortunately, doctors do not visit the
cellar.
Cellars should be frequently cleaned and disinfected, using for the
purpose some of the well-known disinfectants, as formaline, bleaching
powder, or a dilute solution of carbolic acid. It has been found in
large cities, when the spread of such diseases as yellow fever was
imminent, that a general and thorough cleaning up of streets and cellars
with the improved sanitary conditions resulting greatly lowered the
usual death rate.
[Illustration: Fig. 67.--DUNG FUNGUS. (After BUTTERS.)
Often present on surface of unclean vegetables.]
284. Sunlight, Pure Water, and Pure Air as Disinfectants.--The most
effectual and valuable disinfectants are sunlight, pure water, and pure
air. Many kinds of microörganisms, particularly those that are
disease-producing, are destroyed when exposed for a time to sunlight.
The chemical action of the sun's rays is destructive to the organic
material which makes up the composition of many of these organisms,
while higher forms of organic life are stirred into activity by it. The
disinfecting power of sunlight should be made use of to the fullest
extent, not only in the house, but plenty of sunlight should also be
planned for in constructing barns and other buildings where milk-and
meat-producing animals are kept. Pure water is also a disinfectant, but
when water becomes polluted it loses this power. Many disease-producing
organisms are rendered inactive when placed in pure water. Water
contains more dissolved oxygen than air, and apparently a portion of the
oxygen in water is in a more active condition than that in air. Pure
air, too, is a disinfectant; the ozone and hydrogen peroxide and oxides
of nitrogen, which are present in traces, exert a beneficial influence
in oxidizing organic matter. Fresh air and sunlight, acting jointly, are
nature's most effectual disinfectants. Sunshine, fresh air, and pure
water are a health-producing trinity. In discussing the importance of
pure air, water, and sunlight, Ellen H. Richards[97] says:
"The country dweller surrounds his house with evergreens or shade
trees, the city dweller is surrounded with high brick walls.
Blinds, shades, or thick draperies shut out still more, and prevent
the beneficial sunlight from acting its role of germ prevention and
germ destruction. Bright-colored carpets and pale-faced children
are the opposite results which follow. Sunlight, pure air, and pure
water are our common birthright which we often bargain away for
so-called comforts."
And Dr. Woods Hutchinson says of sunlight:
"It is a splendid and matchless servant in the promoting of
healthfulness of the house, for which no substitute has yet been
discovered. It is the foe alike of bacilli and the blues; the best
tonic ever yet invented for the liver and for the scalp, and for
everything between, the only real complexion restorer, and the
deadliest foe of dirt and disease."
[Illustration: FIG. 68.--DIRT AND MANURE EMBEDDED IN SURFACE OF CELERY.]
285. Utensils for Storage of Food.--In order that dishes and household
utensils may be kept in the best sanitary condition, they should be free
from seams, cracks, and crevices where dust and dirt particles can find
lodgment. From the seams of a milk pail that has not been well washed,
decaying milk solids can be removed with the aid of a pin or a
toothpick. This material acts as a "starter" or culture when pure, fresh
milk is placed in the pail, contaminating it and causing it to become
sour. Not only is this true of milk, but also of other foods. Wooden
utensils are not satisfactory for the handling, storage, or preparation
of foods, as it is difficult to keep wood in a sanitary condition.
Uncleanliness of dishes in which foods are placed is too often caused by
the use of foul dishcloths and failure to thoroughly wash and rinse the
dishes. It is always well to rinse dishes with scalding water, as colds
and skin diseases may be communicated from the edges of drinking
glasses, and from forks and spoons, and, unless the dish towels are kept
scrupulously clean, it is more sanitary to drain the dishes than to wipe
them.
286. Contamination from Unclean Dishcloths.--When the dishcloth is
foul, the fat absorbed by the fibers becomes rancid, the proteids
undergo putrefaction changes with formation of ill-smelling gases
containing nitrogen, the carbohydrates ferment and are particularly
attractive to flies, and all the various disease germs collected on the
surface of the dishcloth are, along with the rancid fat and other
putrifying materials, distributed over the surface of the dishes with
which the cloth comes in contact.
[Illustration: FIG. 69.--CONTAMINATION OF WELL WATER FROM SURFACE DRAINAGE.
(After Farmers' Bulletin, U. S. Dept. Agr.)]
287. Refrigeration.--At a low temperature the insoluble or unorganized
ferments become inactive, but the chemical ferments or enzymes are still
capable of carrying on fermentation. Thus it is that a food, when placed
in a refrigerator or in cold storage, continues to undergo chemical
change. An example of such enzymic action is the curing of beef and
cheese in cold storage. A small amount of ventilation is required when
foods are refrigerated, just sufficient to keep up a slight circulation
of air. It seems not to be generally understood that all fermentation
changes do not cease when food is placed in refrigerators, and this
often leads to neglect in their care. Cleanliness is equally as
essential, or more so, in the refrigeration of food as in its handling
in other ways. Too often the refrigerator is neglected, milk and other
food is spilt, filling the cracks, and slow decomposition sets in. A
well-cared-for refrigerator is an important factor in the preservation
of food, but when it is neglected, it becomes a source of contamination.
Unclean vegetables and food receptacles, impure ice and foul air, are
the most common forms of contamination. The chemical changes which
foods undergo during refrigeration are such as result in softening of
the tissues.
288. Soil.--The soil about dwellings and places where foods are stored
frequently becomes polluted with decaying animal and vegetable matter,
and in such soils disease-producing organisms readily find lodgment.
Poorly drained soils containing an excess of vegetable matter furnish a
medium in which the tapeworm and the germs of typhoid fever, lockjaw,
and various diseases affecting the digestive tract, may propagate. The
wind carries the dust particles from these contaminated places into
unprotected food, where they cause fermentation changes and the disease
germs multiply. In considering the sanitary condition of a locality, the
character of the soil is an important factor. Whenever there is reason
to suspect that a soil is unsanitary, it should be disinfected with lime
or formaldehyde. Soils about dwellings need care and frequent
disinfecting to keep them in a sanitary condition, equally as much as do
the rooms in the dwellings.[99] In the growing of garden vegetables,
frequently large quantities of fertilizers of unsanitary character are
used, and vegetables often retain mechanically on their surfaces
particles of these. To this dirt clinging to the vegetables have been
traced diseases, as typhoid fever and various digestion disorders.
289. Disposal of Kitchen Refuse.--Refuse, as vegetable parings, bones,
and meat scraps, unless they are used for food for animals or collected
as garbage, should preferably be burned; then there is no danger of
their furnishing propagating media for disease germs. Garbage cans
should be kept clean, and well covered to protect the contents from
flies. Where the refuse cannot be burned, it should be composted. For
this, a well-drained place should be selected, and the refuse should be
kept covered with earth to keep off the flies and absorb the odors that
arise from the fermenting material, and to prevent its being carried
away by the wind. Lime should be sprinkled about the compost heap, and
from time to time it should be drawn away and the place covered with
clean earth. It is very unsanitary to throw all of the kitchen refuse in
the same place year after year without resorting to any means for
keeping the soil in a sanitary condition. Although composting refuse is
not as sanitary as burning, it is far more sanitary than neglecting to
care for it at all, as is too frequently the case.
Ground polluted with kitchen refuse containing large amounts of fatty
material and soap becomes diseased, so that the natural fermentation
changes fail to take place, and the soil becomes "sewage sick" and gets
in such a condition that vegetation will not grow. Failure to properly
dispose of kitchen refuse is frequently the cause of the spread of germ
diseases, through the dust and flies that are attracted by the material
and carry the germs from the refuse pile to food.
[Illustration: FIG. 70.--PLUMBING OF SINK.
1, 1, house side of trap, filled with water; 2, vent pipe; 3, drain pipe
connecting with sewer.]
Where there is no drainage system, disposal of the liquid refuse is a
serious problem. Drain basins and cesspools are often resorted to, and
these may become additional sources of contamination. As stated in the
chapter on well water, direct communication is frequently established
between such places and shallow wells. Where the only place for the
disposal of waste water is the surface of the ground, it should be
thrown some distance from the house and where it will drain from and not
toward the well. The land should be well drained and open to the
sunlight. Coarse sand and lime should be sprinkled over it frequently,
and occasionally the soil should be removed and replaced with fresh.
Sunlight, aëration, and disinfection of the soil and good drainage are
necessary, in order to keep in a sanitary condition the place where the
dish water is thrown.
Poor plumbing is often the cause of contaminated food. The gases which
escape from unclean traps may carry with them solid particles of organic
matter in various stages of decay. The "house side" of traps always
ventilates into the rooms, and hence it is important that they be kept
scrupulously clean. Where the drip pipe from the refrigerator drains
directly into the sewerage system, there is always danger. Special
attention should be given to the care of plumbing near places where
foods are stored. Frequently there are leaky joints due to settling of
the dwellings or to extreme changes in temperature, and the plumbing
should be occasionally inspected by one familiar with the subject.[100]
290. General Considerations.--In order to keep food in the most
wholesome condition, special care should be taken that all of its
surroundings are sanitary. The air, the dishes in which the food is
placed, the refrigerator, cellar or closet where stored, and the other
food with which it comes in contact, all influence the wholesomeness or
cause contamination. A food may contain sufficient nutrients to give it
high value, and yet, on account of products formed during fermentation,
be poisonous. Foods are particularly susceptible to putrefaction
changes, and chemicals and preservatives added as preventives, with a
view of retarding these changes, are objectionable, besides failing to
prevent all fermentation from taking place. Intelligent thought should
be exercised in the care of food, for the health of the consumer is
largely dependent upon the purity and wholesomeness of the food supply.
[Illustration: FIG. 71.--A PETRI DISH, SHOWING COLONIES OF
BACTERIA PRODUCED BY ALLOWING A HOUSE FLY TO CRAWL OVER SURFACE.
(From Minnesota Experiment Station Bulletin No. 93.)]
CHAPTER XXI
LABORATORY PRACTICE
Object of Laboratory Practice, Laboratory Note-book, and Suggestions
for Laboratory Practice.--The aim of the laboratory practice is to give
the students an idea of the composition, uses, and values of food
materials, and the part which chemistry takes in sanitation and
household affairs; also to enable them by simple tests to detect some of
the more common adulterants in foods.
Before performing an experiment, the student is advised to review those
topics presented in the text which have a bearing upon the experiment,
so that a clear conception may be gained of the relationship between the
laboratory work and that of the class room. The student should endeavor
to cultivate the power of observation and to grasp the principle
involved in the work, rather than do it in a merely mechanical and
perfunctory way. Neatness is one of the essentials for success in
laboratory practice, and too much emphasis cannot be laid upon this
requisite to good work. The student should learn to use his time in the
laboratory profitably and economically. He should obtain a clear idea of
what he is to do, and then do it to the best of his ability. If the
experiment is not a success, repeat it. While the work is in progress it
should be given undivided attention. Care should be exercised to prevent
anything getting into the sinks that will clog the plumbing; soil,
matches, broken glass, and paper should be deposited in the waste jars.
[Illustration: FIG. 72.--APPARATUS USED IN LABORATORY WORK.
See page 301 for names.]
A careful record of the experiments should be kept by each student in a
suitable note-book. It is suggested that those students desiring more
time in writing out the experiments than the laboratory period affords,
take notes as they make the various tests, and then amplify and
rearrange them in the evening study time. The final writing up of the
notes should, however, be done before the next laboratory period.
Careful attention should be given to the spelling, language, and
punctuation, and the note-book should represent the student's individual
work. He who attempts to cheat by copying the results of others, only
cheats himself. In recording the results of an experiment, the student
should state briefly and clearly the following:
1. Number and title of experiment.
2. How the experiment is performed.
3. What was observed.
4. What the experiment proves.
[Illustration: FIG. 73.--BALANCE AND WEIGHTS.]
LIST OF APPARATUS USED IN EXPERIMENTS
1 Crucible Tongs
2 Evaporating Dishes
1 Casserole
6 Beakers
12 Test Tubes
1 Wooden Stand
1 Test Tube Stand
1 Sand Bath
2 Funnels
1 Tripod
1 Stoddart Test Tube Clamp
1 Test Tube Brush
1 Burner and Tubing
2 Stirring Rods
6 Watch Glasses
2 Erlenmeyer Flasks
1 Package Filter Paper
1 Box Matches
1 Wire Gauze
2 Burettes
1 Porcelain Crucible
1 Aluminum Dish
Directions for Weighing.--Place the dish or material to be weighed in
the left-hand pan of the balance. With the forceps lay a weight from the
weight box on the right-hand pan. Do not touch the weights with the
hands. If the weight selected is too heavy, replace it with a lighter
weight. Add weights until the pans are counterpoised; this will be
indicated by the needle swinging nearly as many divisions on one side of
the scale as on the other. The brass weights are the gram weights. The
other weights are fractions of a gm. The 500, 200, 100 mg. (milligram)
weights are recorded as 0.5, 0.2, and 0.1 gm. The 50, 20, and 10 mg.
weights as 0.05, 0.02, and 0.01 gm. If the 10, and 2 gm., and the 200,
the 100, and the 50 mg. weights are used, the resulting weight is 12.35
gms. No moist substances should ever come in contact with the scale
pans. The weights and forceps should always be replaced in the weight
box. Too much care and neatness cannot be exercised in weighing.
[Illustration: FIG. 74.]
[Illustration: FIG. 75.--Pouring Reagent from Bottle.]
Directions for Measuring.--Reagents are measured in graduated
cylinders (see Fig. 74). When the directions call for the addition of 5
or 10 cc. of a reagent, unless so directed it is not absolutely
necessary to measure the reagent in a measuring cylinder. A large test
tube holds about 30 cc. of water. Measure out 5 cc. of water and
transfer it to a large test tube. Note its volume. Add approximately 5
cc. of water directly to the test tube. Measure it. Repeat this
operation until you can judge with a fair degree of accuracy the part of
a test tube filled by 5 cc. In the experiments where a burette is used
for measuring reagents, the burette is first filled with the reagent by
means of a funnel. The tip of the burette is allowed to fill before the
readings are made, which are from the lowest point or meniscus. When
reagents are removed from bottles, the stopper should be held between
the first and second fingers of the right hand (see Fig. 75). Hold the
test tube or receptacle that is to receive the reagent in the left hand.
Pour the liquid slowly until the desired amount is secured. Before
inserting the stopper, touch it to the neck of the bottle to catch the
few drops on the edge, thus preventing their streaking down the sides of
the bottle on to the shelf. Replace the bottle in its proper place.
Every precaution should be taken to prevent contamination of reagents.
[Illustration: FIG. 76.--MICROSCOPE AND ACCESSORIES.
1, eye-piece or ocular; 2, objective; 3, stage; 4, cover glass; 5,
slide; 6, mirror.]
Use of the Microscope.--Special directions in the use of the
microscope will be given by the instructor. The object or material to be
examined is placed on a microscopical slide. Care should be exercised to
secure a representative sample, and to properly distribute the substance
on the slide. If a pulverized material is to be examined, use but little
and spread it in as thin a layer as possible. If a liquid, one or two
drops placed on the slide will suffice. The material on the slide is
covered with a cover glass, before it is placed on the stage of the
microscope. In focusing, do not allow the object glass of the microscope
to come in contact with the cover glass. Focus upward, not downward.
Special care should be exercised in focusing and in handling the
eye-piece and objective. A camel's-hair brush, clean dry chamois skin,
or clean silk only should be used in polishing the lenses. Always put
the microscope back in its case after using.
Experiment No. 1
Water in Flour
Carefully weigh a porcelain or aluminum dish. (Porcelain must be used if
the ash is to be determined on the same sample.) Place in it about 2 gm.
of flour; record the weight; then place the dish in the water oven for
at least 6 hours. After drying, weigh again, and from the loss of weight
calculate the per cent of water in the flour. (Weight of flour and dish
before drying minus weight of flour and dish after drying equals weight
of water lost. Weight of water divided by weight of flour taken,
multiplied by 100, equals the per cent of water in the flour.)
How does the amount of water you obtained compare with the amount given
in the tables of analysis?
Experiment No. 2
Water in Butter
Carefully weigh a clean, dry aluminum dish, place in it about 2 gms. of
butter, and weigh again. Record the weights. Place the dish containing
butter in the water oven for 5 or 6 hours and then weigh. The loss in
weight represents the water in the butter. Calculate the per cent of
water. Care must be taken to get a representative sample of the butter
to be tested; preferably small amounts should be taken with the butter
trier from various parts of the package.
Experiment No. 3
Ash in Flour
Place the porcelain dish containing flour from the preceding experiment
in a muffle furnace and let it remain until the organic matter is
completely volatilized. Cool, weigh, and determine the per cent of ash.
The flour should be burned at the lowest temperature necessary for
complete combustion.
Experiment No. 4
Nitric Acid Test for Nitrogenous Organic Matter
To 3 cc. of egg albumin in a test tube add 2 cc. of HNO_{3} (conc.) and
heat. When cool add NH_{4}OH. The nitric acid chemically reacts upon the
albumin, forming yellow xanthoprotein. What change occurs in the
appearance of the egg albumin when the HNO_{3} is added? Is this a
physical or chemical change? What is the name of the compound formed?
What change occurs on adding NH_{4}OH?
Experiment No. 5
Acidity of Lemons
With a pipette measure into a small beaker 2 cc. of lemon juice. Add 25
cc. of water and a few drops of phenolphthalein indicator. From the
burette run in N/10 KOH solution until a faint pink tinge remains
permanently. Note the number of cubic centimeters of KOH solution
required to neutralize the citric acid in the lemon juice. Calculate the
per cent of citric acid.
(1 cc. of N/10 KOH solution equals 0.00642 gm. citric acid. 1 cc. of
H_{2}O weighs 1 gm. Because of sugar and other matter in solution 1 cc.
of lemon juice weighs approximately 1.03 gm.)
1. What is the characteristic acid of lemons? 2. What is the salt formed
when the lemon juice is neutralized by the KOH solution? 3. Describe
briefly the process for determining the acidity of lemon juice. 4. What
per cent of acidity did you obtain? 5. How does this compare with the
acidity of vinegar?
Experiment No. 6
Influence of Heat on Potato Starch Grains
With the point of a knife scrape slightly the surface of a raw potato
and place a drop of the starchy juice upon the microscopical slide.
Cover with cover glass and examine under the microscope.
In the evaporating dish cook a small piece of potato, then place a very
small portion upon the slide, and examine with the microscope.
Make drawings of the starch grains in raw and in cooked potatoes.
Experiment No. 7
Influence of Yeast on Starch Grains
Moisten a small portion of the dough prepared with yeast and with the
stirring rod place a drop of the starchy water upon the slide. Cover
with cover glass and examine under the microscope.
Repeat, examining a drop of starchy water washed from flour.
Make drawing of wheat starch grain in flour and in dough prepared with
yeast.
Experiment No. 8
Mechanical Composition of Potatoes
Wash one potato. Weigh, then peel, making the peeling as thin as
possible. Weigh the peeled potato and weigh the peeling or refuse.
Calculate the per cent of potato that is edible and the per cent that is
refuse.
Experiment No. 9
Pectose from Apples
Reduce a small peeled apple to a pulp. Squeeze the pulp through a clean
cloth into a beaker. Add 10 cc. H_{2}O and heat on a sand bath to
coagulate the albumin. Filter, adding a little hot water if necessary.
To the filtrate add 5 cc. alcohol. The precipitate is the pectose
material.
1. Is the pectose from the apple soluble? 2. Is it coagulated by heat?
3. Is it soluble in alcohol?
Experiment No. 10
Lemon Extract
To 5 cc. of the extract in a test tube add an equal volume of water. A
cloudy appearance indicates the presence of lemon oil. If the solution
remains clear after adding the water, the extract does not contain lemon
oil.
Why does the extract containing lemon oil become cloudy on adding water?
Experiment No. 11
Vanilla Extract
Pour into a test tube 5 cc. of the extract to be tested. Evaporate to
one third. Then add sufficient water to restore the original volume. If
a brown, flocculent precipitate is formed, the sample contains pure
vanilla extract. Resin is present in vanilla beans and is extracted in
the essence. The resin is readily soluble in 50 per cent alcohol. If
the alcohol is removed from the extract, the excess of resin is
precipitated, or if free from alkali, it may be precipitated by diluting
the original solution with twice its volume of water. Test the two
samples and compare.
(Adapted from Leach, "Food Inspection and Analysis.")
1. Describe the appearance of each sample after evaporating and adding
water. 2. Which sample contains pure vanilla extract? 3. State the
principle underlying this test.
Experiment No. 12
Testing Olive Oil for Cotton Seed Oil
Pour into a test tube 5 cc. of the oil to be tested and 5 cc. of
Halphen's Reagent. Mix thoroughly. Plug the test tube loosely with
cotton, and heat in a bath of boiling saturated brine for 15 minutes. If
cotton seed oil is present, a deep red or orange color is produced. Test
two samples and compare.
Halphen's Reagent.--Mix equal volumes of amyl alcohol and carbon
disulphid containing about one per cent of sulphur in solution.
(Adapted from Leach, "Food Inspection and Analysis.")
Experiment No. 13
Testing for Coal Tar Dyes
Dilute 20 to 30 cc. of the material to 100 cc.; boil for 10 minutes with
10 cc. of a 10 per cent solution of potassium bisulphate and a piece of
white woolen cloth which has previously been boiled in a 0.1 per cent
solution of NaOH and thoroughly washed in water. Remove the cloth from
the solution, wash in boiling water, and dry between pieces of filter
paper. A bright red indicates coal tar dye. If the coloring matter is
entirely from fruit, the woolen cloth will be either uncolored or will
have a faint pink or brown color which is changed to green or yellow by
ammonia and is not restored by washing. This is the Arata test.
(Adapted, Winston, Conn. Experiment Station Report.)
1. Describe Arata's wool test for coal tar dyes. 2. What is the
appearance of the woolen cloth when the coloring matter is entirely from
fruit? 3. What effect has NH_{4}OH upon the color? 4. Why is NaOH used?
5. Why may not cotton cloth be used instead of woolen? 6. What can you
say of the use of coal tar dyes in foods?
Experiment No. 14
Determining the Per Cent of Skin in Beans
Place in an evaporating dish 10 gm. of beans, 50 cc. of water, and 1/2
gm. of baking soda. Boil 10 minutes or until the skins are loosened,
then drain off the water. Add cold water and rub the beans together till
the skins slip off. Collect the skins, place on a watch glass and dry in
the water oven for 1/2 hour. Weigh the dried skins and calculate the per
cent of "skin."
1. What does the soda do? 2. What effect would hard limewater have upon
the skins? 3. How does removal of skins affect food value of beans and
digestibility?
Experiment No. 15
Extraction of Fat from Peanuts
Shell three or four peanuts and with the mortar and pestle break them
into small pieces. Place in a test tube and pour over them about 10 cc.
of ether. Cork the test tube and allow it to stand 30 minutes, shaking
occasionally. Filter on to a watch glass and let stand until the ether
evaporates, and then observe the fat.
1. What is the appearance of the peanut fat? 2. What is the solvent of
the fat? 3. What becomes of the ether? 4. Why should the peanuts be
broken into small pieces?
Experiment No. 16
Microscopic Examination of Milk
Place a drop of milk on a microscopical slide and cover with cover
glass. Examine the milk to detect impurities, as dust, hair, refuse,
etc. Make drawings of any foreign matter present.
Experiment No. 17
Formaldehyde in Cream or Milk
To 10 cc. of milk in a casserole add 10 cc. of the acid reagent. Heat
slowly over the flame nearly to boiling, holding the casserole in the
hand and giving it a slight rotary movement while heating. The presence
of formaldehyde is indicated by a violet coloration varying in depth
with the amount present. In the absence of formaldehyde the solution
slowly turns brown.
Acid Reagent.--Commercial hydrochloric acid (sp. gr. 1.2) containing 2
cc. per liter of 10 per cent ferric chlorid.
(Adapted from Leach, "Food Inspection and Analysis.")
1. How may the presence of formaldehyde in milk be detected? 2. Why in
this test is it necessary to use acid containing ferric chlorid? 3.
Describe the appearance of the two samples of milk after adding the acid
reagent and heating. 4. Which sample showed the presence of
formaldehyde?
Experiment No. 18
Gelatine in Cream or Milk
To 20 cc. of milk or cream in a beaker add 20 cc. of acid mercuric
nitrate and about 40 cc. of H_{2}O. Let stand for a few minutes and
filter. Filtrate will be cloudy if gelatine is present.
Add 1/2 cc. of a dilute solution of picric acid--a heavy yellow
precipitate indicates gelatine.
Acid Mercuric Nitrate.--1 part by weight of Hg, 2 parts HNO_{3} (sp.
gr. 1.42). Dilute 25 times with water.
Experiment No. 19
Testing for Oleomargarine
Apply the following tests to two samples of the material:
Boiling or Spoon Test.--Melt the sample to be tested--a piece about
the size of a chestnut--in a large spoon, hastening the process by
stirring with a splinter. Then, increasing the heat, bring to as brisk a
boil as possible and stir thoroughly, not neglecting the outer edges.
Oleomargarine and renovated butter boil noisily, sputtering like a
mixture of grease and water, and produce no foam, or but very little.
Genuine butter boils with less noise and produces an abundance of foam.
Waterhouse Test.--Into a small beaker pour 50 cc. of sweet milk. Heat
nearly to boiling and add from 5 to 10 gms. of butter or oleomargarine.
Stir with a glass rod until fat is melted. Then place the beaker in cold
water and stir the milk until the temperature falls sufficiently for the
fat to congeal. At this point the fat, if oleomargarine, can easily be
collected into one lump by means of the rod; while if butter, it will
granulate and cannot be collected.
(From Farmers' Bul. 131, U. S. Dept. of Agriculture.)
1. Name two simple tests for distinguishing butter and oleomargarine. 2.
Describe these tests. 3. Why do butter and oleomargarine respond
differently to these tests? 4. Are these tests based upon chemical or
physical properties of the fats?
Experiment No. 20
Testing for Watering or Skimming of Milk
_a._ Fat Content of Milk by Means of Babcock Test.--Measure with
pipette into test bottle 17.6 cc. of milk. Sample should be carefully
taken and well mixed. Measure with cylinder 17.5 cc. commercial
H_{2}SO_{4} and add to milk in test bottle. (See Fig. 25.) Mix acid and
milk by rotating the bottle. Then place test bottles in centrifugal
machine and whirl 5 minutes. Add sufficient hot water to test bottles to
bring contents up to about the 8th mark on stem. Then whirl bottles 2
minutes longer and read fat. Read from extreme lowest to highest point.
Each large division as 1 to 2 represents a whole per cent, each small
division 0.2 of a per cent.
_b._ Determining Specific Gravity by Means of Lactometer.--Pour 150
cc. of milk into 200 cc. cylinder. Place lactometer in milk and note
depth to which it sinks as indicated on stem. Note also temperature of
milk. For each 10° above 60° F. add 1 to the lactometer number, in order
to make the necessary correction for temperature. For example, if milk
has sp. gr. of 1.032 at temperature of 70°, it will be equivalent to sp.
gr. of 1.033 at 60°. Ordinarily milk has a sp. gr. of 1.029 to 1.034. If
milk has sp. gr. less than 1.029, or contains less than 3 per cent fat,
it may be considered watered milk. If the milk has a high sp. gr. (above
1.035) and a low content of fat, some of the fat has been removed.
(For extended direction for milk testing see Snyder's "Dairy Chemistry.")
Experiment No. 21
Boric Acid in Meat
Cut into very small pieces 5 gms, of meat, removing all the fat
possible. Place in an evaporating dish with 20 to 25 cc. of water to
which a few drops of HCl have been added and warm slightly. Dip a piece
of turmeric paper in the meat extract and dry. A rose-red color of the
turmeric paper after drying (turned olive by a weak ammonia solution) is
indicative of boric acid.
1. How may meat be tested for boric acid? 2. Why is HCl added to the
water? 3. Why is the water containing the meat warmed slightly? 4. What
is the appearance of the turmeric paper after being dipped in the meat
extract and dried? 5. What change takes place when it is moistened with
ammonia, and why?
Experiment No. 22
Microscopic Examination of Cereal Starch Grains
Make a microscopic examination and drawings of wheat, corn, rice, and
oat starch grains, comparing them with the drawings of the different
starch grains on the chart. If the material is coarse, pulverize in a
mortar and filter through cloth. Place a drop or two of the starchy
water on the slide, cover with a cover glass, and examine.
Experiment No. 23
Identification of Commercial Cereals
Examine under the microscope two samples of cereal breakfast foods, and
by comparison with the wheat, corn, and oat starch grains previously
examined tell of what grains the breakfast foods are made and their
approximate food value.
Experiment No. 24
Granulation and Color of Flour
Arrange on glass plate, in order of color, samples of all the different
grades of flour. Note the differences in color. How do these differences
correspond with the grades of the flour? Examine the flour with a
microscope, noting any coarse or dark-colored particles of bran or dust.
Rub some of the flour between the thumb and forefinger. Note if any
granular particles can be detected.
Experiment No. 25
Capacity of Flour to absorb Water
Weigh out 15 gms. of soft wheat flour into an evaporating dish; then add
from burette a measured quantity of water sufficient to make a stiff
dough. Note the amount of water required for this purpose. Repeat the
operation, using hard wheat flour.
1. How may the absorptive power of a flour be determined? 2. To what is
it due? 3. Why do some flours absorb more water than others?
Experiment No. 26
Acidity of Flour
Weigh into a flask 20 gms. of flour and add 200 cc. distilled water.
Shake vigorously. After letting stand 30 minutes, filter and then
titrate 50 cc. of the filtrate against standard KOH solution, using
phenolphthalein as indicator, 1 cc. of the alkali equals 0.009 gms.
lactic acid. Calculate the per cent of acid present.
1. How may the acidity of a flour be determined? 2. The acidity is
expressed in percentage amounts of what acid? 3. What per cent of
acidity is found in normal flours? 4. What does a high acidity of a
flour indicate?
Experiment No. 27
Moist and Dry Gluten
Weigh 30 gms. of flour into a porcelain dish. Make the flour into a
stiff dough. After 30 minutes obtain the gluten by washing, being
careful to remove all the starch and prevent any losses. Squeeze the
water from the gluten as thoroughly as possible. Weigh the moist gluten
and calculate the per cent. Dry the gluten in the water oven and
calculate the per cent of dry gluten.
Experiment No. 28
Gliadin from Flour
Place in a flask 10 gms. of flour, 30 cc. of alcohol, and 20 cc. of
water. Cork the flask and shake, and after a few minutes shake again.
Allow the alcohol to act on the flour for an hour, or until the next
day. Then filter off the alcohol solution and evaporate the filtrate to
dryness over the water bath. Examine the residue; to a portion add a
little water; burn a small portion and observe odor.
1. Describe the appearance of the gliadin. 2. What was the result when
water was added? 3. When burned, what was the odor of the gliadin, and
what does this indicate? 4. What is gliadin?
Experiment No. 29
Bread-making Test
Make a "sponge" by mixing together:
12 gm. sugar,
12 gm. yeast (compressed),
4 gm. salt,
175 cc. water (temp. 32° C.).
Let stand 1/2 hour at a temperature of 30° C. In a large bowl, mix with
a knife or spatula 7.7 gms. of lard with 248.6 gms. of flour. Then add
160 cc. of the "sponge," or as much as is needed to make a good stiff
dough, and mix thoroughly, using the spatula. With some flours as small
a quantity as 150 cc. of sponge may be used. If more moisture is
necessary, add H_{2}O. Keep at temperature of 30° C. Allow the dough to
stand 50 minutes to first pulling, 40 minutes to second pulling, and 30
to 50 minutes to the pan. Let it rise to top of pan and then bake for
1/2 hour in an oven at a temperature of 180° C. One loaf of bread is
made of patent flour of known quality as a standard for comparison, and
other loaves of the flours to be tested. Compare the loaves as to size
(cubic contents), color, porosity, odor, taste, nature of crust, and
form of loaf.
Experiment No. 30
Microscopic Examination of Yeast
On a watch glass mix thoroughly a very small piece of yeast with about 5
cc. of water and then with the stirring rod place a drop of this
solution on the microscopical slide, adding a drop of very dilute methyl
violet solution. Cover with the cover glass and examine under the
microscope. The living active cells appear colorless while the decayed
and lifeless ones are stained. Yeast cells are circular or oval in
shape. (See Fig. 46.)
(Adapted from Leach, "Food Inspection and Analysis.")
Experiment No. 31
Testing Baking Powders for Alum
Place about 2 gms. of flour in a dish with 1/2 gm. baking powder. Add
enough water to make a dough and then 2 or 3 drops of tincture of
logwood and 2 or 3 drops of ammonium carbonate solution. Mix well and
observe; a blue color indicates alum. Try the same test, using flour
only for comparison.
1. How do you test a baking powder for alum? 2. What difference in color
did you observe in the test with the baking powder containing alum and
in that with the flour only? 3. Why is the (NH_{4})_{2}CO_{3} solution
used?
Experiment No. 32
Testing Baking Powders for Phosphoric Acid
Dissolve 1/2 gm. of baking powder in 5 cc. of H_{2}O and 3 cc. HNO_{3}.
Filter and add 3 cc. ammonium molybdate. Heat gently. A yellow
precipitate indicates phosphoric acid.
1. How do you test a baking powder for phosphoric acid? 2. What is the
yellow precipitate obtained in this test?
Experiment No. 33
Testing Baking Powders for Ammonia
Dissolve 1/2 gm. of material in 10 cc. water; filter off any insoluble
residue and to the filtrate add 2 or 3 cc. NaOH and apply heat. Test the
gas given off with moistened turmeric paper. If NH_{3} is present, the
paper will be colored brown. Do not allow the paper to come in contact
with the liquid or sides of the test tube. (Perform the tests on two
samples of baking powder.)
1. How do you test a baking powder for ammonia? 2. Why do you add NaOH?
3. Why must you be careful not to let the turmeric paper touch the sides
of the test tube or the liquid?
Experiment No. 34
Vinegar Solids
Into a weighed aluminum or porcelain dish pour 10 cc. of vinegar. Weigh
and then evaporate over boiling water. To drive off the last traces of
moisture dry in the water oven for an hour. Cool and weigh. Calculate
the per cent of solids. Observe the appearance of the solids. Test both
samples and compare.
1. How may the per cent of solids in vinegar be determined? 2. Describe
the appearance of the solids from the good and from the poor sample of
vinegar. 3. What is the legal standard for vinegar solids in your state?
Experiment No. 35
Specific Gravity of Vinegar
Pour 170 cc. vinegar into 200 cc. cylinder. Place a hydrometer for heavy
liquids (sp. gr. 1 to 1.1) in the cylinder. Note the depth to which it
sinks and the point registered on the scale on the stem. Note
temperature of vinegar. Record specific gravity of vinegar.
1. What effect would addition of water to vinegar have upon its specific
gravity? 2. What effect would addition of such material as sugar have
upon specific gravity? 3. Why should the specific gravity of vinegar be
fairly constant? 4. What would be the weight of 1000 cc. of vinegar
calculated from the specific gravity?
Experiment No. 36
Acidity of Vinegar
Into a small beaker pour 6 cc. of vinegar and 10 cc. of water and a few
drops of phenolphthalein indicator. Run in standard KOH solution from a
burette until a faint pink tinge remains permanently. Note the number of
cubic centimeters of KOH solution required to neutralize the acid.
Divide this number by 10, which will give approximately the per cent of
acetic acid.
1. How may the per cent of acidity of vinegar be determined? 2. Why was
phenolphthalein used? 3. Why was KOH used? 4. What acids does vinegar
contain? 5. What is the legal requirement in this state for acetic acid
in vinegar? 6. How did the acidity you obtained compare with this legal
requirement?
Experiment No. 37
Deportment of Vinegar with Reagents
To 10 cc. of vinegar in a test tube add 8 or 10 drops of lead
sub-acetate and shake. Observe the precipitate. Lead sub-acetate
precipitates mainly the malic acid which is always present in cider
vinegar.
1. How may the presence of malic acid in a vinegar be detected? 2.
Describe the precipitate. 3. What does malic acid in a vinegar indicate?
Experiment No. 38
Testing Mustard for Turmeric
Place 1 gm. of ground mustard on a small watch glass and moisten
slightly with water. Add 2 or 3 drops of NH_{4}OH, stirring well with a
glass rod. A brown color indicates turmeric present in considerable
quantity.
Test a sample of good mustard and one adulterated with turmeric and
compare the results.
Experiment No. 39
Examination of Tea Leaves
Soak a small amount of tea and unroll 8 or 10 of the leaves. Make a
drawing of a tea leaf. Observe the proportion of stems in each of three
samples of tea; also the relative proportion of large and small leaves.
Observe if the leaves are even as to size and of a uniform color.
Experiment No. 40
Action of Iron Compounds upon Tannic Acid
Make an infusion of tea by placing 3 gms. of tea in 100 cc. of hot water
and stirring well. Filter off some of the infusion and test 5 cc. with
ferrous sulphate solution made by dissolving 1 gm. FeSO_{4} in 10 cc.
H_{2}O and filtering. Note the result.
1. What change in color did you observe when the ferrous sulphate
solution was added to the tea infusion? 2. What effect would waters
containing iron have upon the tea infusion?
Experiment No. 41
Identification of Coffee Berries
Examine Rio, Java, and Mocha coffee berries. Describe each. Note the
characteristics of each kind of coffee berry.
Experiment No. 42
Detecting Chicory in Coffee
Fill a beaker with water and place about a teaspoonful of ground coffee
on the surface. If much of the ground material sinks and it imparts a
dark brown color to the lower portion of the liquid, it is an indication
of the presence of chicory. Pure coffee floats on water. Chicory has a
higher specific gravity than coffee.
1. How may the presence of chicory in ground coffee be detected? 2. Why
does coffee float on the water while chicory sinks? 3. What effect does
chicory have upon the color of water?
Experiment No. 43
Testing Hard and Soft Waters
Partially fill a large cylinder with very hard water. This may be
prepared by dissolving 0.1 to 0.2 gm. calcium chloride in 500 cc. of
ordinary water. Add to this a measured quantity of soap solution. Mix
well and notice how many cubic centimeters of soap solution must be used
before a permanent lather is formed, also notice the precipitate of
"lime soap." Repeat this experiment, using either rain or distilled
water, and compare the cubic centimeters of soap solution used with that
in former test. Repeat the test, using tap water.
Soap Solution.--Scrape 10 gms. of castile soap into fine shavings and
dissolve in a liter of alcohol, dilute with 1/3 water. Filter if not
clear and keep in a tightly stoppered bottle.
1. Why is more soap required to form a lather with hard water than with
soft water? 2. What is meant by "lime soap"? Describe its appearance. 3.
How may hard waters be softened for household purposes?
Experiment No. 44
Solvent Action of Water on Lead
Put 1 gm. of clean bright lead shavings into a test tube containing 10
cc. of distilled water. After 24 hours decant the clear liquid into a
second test tube, acidify slightly with HCL, and add a little hydrogen
sulphid water. A black or brownish coloration indicates lead in
solution.
(Adapted from Caldwell and Breneman, "Introductory Chemical Practice.")
Under what conditions may lead pipes be objectionable?
Experiment No. 45
Suspended Matter in Water
Place a drop of water on the microscopical slide, cover with cover
glass, and examine with the microscope. Note the occurrence and
appearance of any suspended matter in the water.
Experiment No. 46
Organic Matter in Water
Pour into the evaporating dish 100 cc. H_{2}O and evaporate to dryness
over the sand bath. Ignite the solids. If the solids blacken when
ignited, the water contains organic matter.
Experiment No. 47
Deposition of Lime by Boiling Water
Boil for a few minutes about 200 cc. of water in a flask. After the
water is cool, note any sediment of lime or turbidity of the water due
to expelling the carbon dioxid.
1. What is meant by a "hard" water? 2. What do the terms "temporary" and
"permanent" hardness of water mean? 3. What acts as a solvent of the
lime in water? 4. Why does boiling cause the lime to be deposited?
Experiment No. 48
Qualitative Tests for Minerals in Water
Test for Chlorids.--To 10 cc. of H_{2}O add a few drops of HNO_{3} and
2 cc. of AgNO_{3}. A white precipitate indicates the presence of
chlorids, usually in the form of sodium chlorid.
Test for Sulphates.--To 10 cc. of water add 2 cc. of dilute HCl and 2
cc. of BaCl_{2}. A cloudiness or the formation of a white precipitate
indicates the presence of sulphates.
Test for Iron.--If a brown sediment is formed in water exposed to the
air for some time, it is probably iron hydroxid. To 10 cc. of the water
add a few drops of HNO_{3}, heat, and then add 1/2 cc. of NH_{4}CNS. A
red color indicates the presence of iron.
Test for CaO and MgO.--To 10 cc. of H_{2}O add 5 cc. NH_{4}OH. If a
precipitate forms, filter it off, and to the filtrate add 3 cc. NH_{4}Cl
and 5 cc. (NH_{4})_{2}C_{2}O_{4}. The precipitate is CaC{2}O_{4}, and
the filtrate contains the magnesia. Filter and add 5 cc. Na_{3}PO_{4} to
precipitate MgNH_{4}PO_{4}.
1. How would you test a water to detect the presence of organic matter?
2. Name some mineral impurities often found in water. 3. Describe the
test for chlorids; for sulphates; for iron; for lime; for magnesium. 4.
Of the two classes of impurities found in water, which is the more
harmful? 5. Name three ways of purifying waters known to be impure, and
tell which is the most effectual.
Experiment No. 49
Testing for Nitrites in Water
To 50 cc. of water in a small beaker add with a pipette 2 cc. of
naphthylamine hydrochloride and then 2 cc. of sulphanilic acid. Stir
well and wait 20 minutes for color to develop. A pink color indicates
nitrites.
REAGENTS USED
Sulphanilic Acid.--Dissolve 5 gm. in 150 cc. of dilute acetic acid;
sp. gr. 1.04.
Naphthylamine Hydrochloride.--Boil 0.1 gm. of solid [Greek:
a]-amidonaphthaline (naphthylamine) in 20 cc. of water, filter the
solution through a plug of absorbent cotton, and mix the nitrate with
180 cc. of dilute acetic acid. All water used must be free from
nitrites, and all vessels must be rinsed out with such water before
tests are applied.
1. Would a water showing the presence of nitrites be a safe drinking
water? Why? 2. What are nitrites? 3. What does the presence of nitrites
indicate? 4. Are small amounts of nitrites, when not associated with
bacteria, injurious?
REVIEW QUESTIONS
CHAPTER I
GENERAL COMPOSITION OF FOODS
1. To what extent is water present in foods? 2. What foods contain the
most, and what foods the least water? 3. How does the water content of
some foods vary with the hydroscopicity of the air? 4. How may changes
in water content of foods affect their weight? 5. Why is it necessary to
consider the water content of foods in assigning nutritive values? 6.
How is the dry matter of a food determined? 7. Why is the determination
of the water in a food often a difficult process? 8. What is the ash or
mineral matter of a food? 9. How is it obtained? 10. What is its source?
11. Of what is the ash of plants composed? 12. What part in plant life
do these ash elements take? 13. Name the ash elements essential for
plant growth. 14. Which of the mineral elements take the most essential
part in animal nutrition? 15. In what form are these elements usually
considered most valuable? 16. Why is sodium chloride or common salt
necessary for animal life? 17. How do food materials differ in ash
content? 18. Define organic matter of foods. 19. How is it obtained? 20.
Of what is it composed? 21. Into what is the organic matter converted
when it is burned? 22. Give the two large classes of organic compounds
found in food materials. 23. Name the various subdivisions of the
non-nitrogenous compounds. 24. What are the carbohydrates? 25. Give
their general composition. 26. What is cellulose? 27. Where is it found?
28. What is its function in plants? 29. What is its food value? 30. In
what way may cellulose be of value in a ration? 31. In what way may it
impart a negative value to a ration? 32. What is starch? 33. Where is
it mainly found in plants? 34. Give the mechanical structure of the
starch grain. 35. Why is starch insoluble in cold water? 36. How do
starch grains from different sources differ in structure? 37. What
effect does heat have upon starch? 38. Define hydration of starch. 39.
Under what conditions does this change take place? 40. What value as a
nutrient does starch possess? 41. What is sugar? 42. How does it
resemble and how differ in composition from starch? 43. What are the
pectose substances? 44. How are they affected by heat? 45. What food
value do they possess? 46. What is nitrogen-free-extract? 47. How is it
obtained? 48. How may the nitrogen-free-extract of one food differ from
that of another? 49. What are the fats? 50. How do they differ in
composition from the starches? 51. Why does fat when burned or digested
produce more heat than starch or sugar? 52. Name the separate fats of
which animal and vegetable foods are composed. 53. Give some of the
physical characteristics of fat. 54. What is the iodine absorption
number of a fat? 55. How does the specific gravity of fat compare with
that of water? 56. Into what two constituents may all fats be separated?
57. What is ether extract? 58. How does the ether extract in fats vary
in composition and nutritive value? 59. What are the organic acids? 60.
Name those most commonly met with in foods. 61. What nutritive value do
they possess? 62. What dietetic value? 63. What value are they to the
growing plant? 64. What organic acids are found in animal foods? 65.
What are the essential oils? 66. How do they differ from the fixed oils,
or fats? 67. What property do the essential oils impart to foods? 68.
What food value do they possess? 69. What dietetic value? 70. What are
the mixed compounds? 71. How may a compound impart a negative value to a
food? 72. What is the nutritive value of the non-nitrogenous compounds,
taken as a class? 73. Why is it necessary that nitrogenous and
non-nitrogenous compounds be blended in a ration? 74. What are the
nitrogenous compounds? 75. How do they differ from the non-nitrogenous
compounds? 76. Name the four subdivisions of the nitrogenous compounds.
77. What is protein? 78. What is characteristic as to its nitrogen
content? 79. What are some of the derivative products that can be
obtained from the protein molecule? 80. How does the protein content of
animal bodies compare with that of plants? 81. Name the various
subdivisions of the proteins. 82. What is albumin, and how may it be
obtained from a food? 83. What is globulin, and how is it obtained from
a food? 84. Give some examples of globulins. 85. What are the
albuminates, and how are they affected by the action of acids and
alkalies? 86. What are the peptones, and how do they differ from the
albumins? 87. How are the peptones produced from other proteids? 88.
What are the insoluble proteids? 89. Give an example. 90. Which of the
proteids are found to the greatest extent in foods? 91. Why may proteids
from different sources vary in their nutritive value? 92. What general
change do the proteids undergo during digestion? 93. What is crude
protein? 94. How is the crude protein content of a food calculated? 95.
Why is the nitrogen content of a food more absolute than the crude
protein content? 96. What food value do the proteins possess? 97. Why
may proteins serve so many functions in the body? 98. Why is protein
necessary as a nutrient? 99. What is the effect of an excess of protein
in the ration? 100. What is the effect of a scant amount of protein in a
ration? 101. What are the albuminoids? 102. Name borne materials that
contain large amounts of albuminoids. 103. What food value do the
albuminoids possess? 104. What are the amids? 105. How are they formed
in plants? 106. What is their source in animals? 107. What general
changes does the element nitrogen undergo in plant and animal bodies?
108. What is the food value of the amids? 109. What are the alkaloids?
110. What is their food value? 111. What effect do some alkaloids exert
upon the animal body? 112. How may they be produced in animal foods?
113. What general relationship exists between the various nitrogenous
compounds? 114. Why is it essential that the animal body be supplied
with nitrogenous food in the form of proteids? 115. Name the cycle of
changes through which the element nitrogen passes in plant and animal
bodies.
CHAPTER II
CHANGES IN COMPOSITION OF FOODS DURING COOKING AND PREPARATION
116. How do raw and cooked foods compare in general composition? 117. In
what ways are foods acted upon during cooking? 118. What causes chemical
changes to take place during cooking? 119. What are the principal
compounds that are changed during the process of cooking? 120. How does
cooking affect the cellulose of foods? 121. What change does starch
undergo during cooking? 122. When foods containing starch are baked,
what change occurs? 123. How are the sugars acted upon when foods are
cooked? 124. What effect does dry heat have upon sugar? 125. What change
occurs to the fats during cooking? 126. How does this affect nutritive
value? 127. What changes do the proteids undergo during cooking? 128.
Why does the action of heat affect various proteids in different ways?
129. Why are chemical changes, as hydration, often desirable in the
cooking and preparation of foods? 130. What physical changes do
vegetable and animal tissues undergo when cooked? 131. How do foods
change in weight during cooking? 132. Why is a prolonged high
temperature unnecessary to secure the best results in cooking? 133. To
what extent is the energy of fuels utilized for producing mechanical and
chemical changes in foods during cooking? 134. What effect does cooking
have upon the bacterial flora of foods? 135. In what ways do bacteria
exert a favorable influence in the preparation of foods? 136. How may
certain classes of bacteria exert unfavorable changes in the preparation
of foods? 137. What are the insoluble ferments? 138. What are the
soluble ferments? 139. What part do they take in animal and plant
nutrition? 140. Define aerobic ferments. 141. Define anaërobic ferments.
142. What general relationship exists between the chemical, physical,
and bacteriological changes that take place in foods? 143. Why should
foods also possess an esthetic value? 144. What kinds of colors should
be used in the preparation of foods? 145. What processes should be used
for removal of coloring materials from foods?
CHAPTER III
VEGETABLE FOODS
146. Give the general composition of vegetable foods as a class. 147.
How do vegetable foods differ from animal foods? 148. Name some
vegetables which contain the maximum, and some which contain the minimum
percentage of protein. 149. Give the general composition of potatoes.
150. Of what is the dry matter mainly composed? 151. How much of the
crude protein of potatoes is true protein? 152. What ratio exists
between the nitrogenous and non-nitrogenous compounds in the potato?
153. Give the chemical composition of the potato. 154. What influence do
different methods of boiling have upon the crude protein content of
potatoes? 155. To what extent are the nutrients of potatoes digested and
absorbed by the body? 156. What value do potatoes impart to the ration?
157. How do sweet potatoes differ in chemical composition and food value
from white potatoes? 158. How do carrots differ in composition from
potatoes? 159. What is characteristic of the dry matter of the carrot?
160. How do carrots and milk differ in composition? 161. To what is the
color of the carrot due? 162. To what extent are the nutrients removed
in the cooking of carrots? 163. What is the value of carrots in a
ration? 164. Give the characteristics of the composition of parsnips.
165. How does the starch of parsnips differ from that of potatoes? 166.
How does the mineral matter of parsnips differ from that of potatoes?
167. How does the cabbage differ in general composition from many
vegetables? 168. To what extent are nutrients extracted in the boiling
of cabbage? 169. Give the nutritive value of cabbage. 170. How does the
cauliflower differ from cabbage? 171. Give the general composition of
beets. 172. Give the general composition of cucumbers. 173. What
nutritive value has lettuce? 174. Give the composition and dietetic
value of onions. 175. How does the ratio of nitrogenous and
non-nitrogenous compounds in spinach differ from that in many other
vegetables? 176. Give the general composition and nutritive value of
asparagus. 177. How much nutritive material do melons contain? 178. What
are the principal compounds of tomatoes? 179. What nutrients do they
supply to the ration? 180. In the canning of tomatoes, why is it
desirable to conserve the juices? 181. How does sweet corn differ in
composition from fully matured corn? 182. What nutritive value does the
egg plant possess? 183. What are the principal nutrients of squash? 184.
What nutritive material does celery contain? 185. To what does celery
owe its dietetic value? 186. Why are vegetables necessary in a ration?
187. Why is it not possible to value many vegetable foods simply on the
basis of percentage of nutrients present? 188. Name the miscellaneous
compounds which many vegetables contain, and the characteristics which
these may impart. 189. Why is it necessary to consider the sanitary
conditions of vegetables? 190. How do canned vegetables differ in
composition and food value from fresh vegetables? 191. What proportion
of vegetables is refuse and non-edible parts? 192. Why is it necessary
to consider the refuse of a food in determining its nutritive value?
CHAPTER IV
FRUITS
193. To what extent do fruits contain water and dry matter? 194. Give
the general composition of fruits. 195. What compounds impart taste and
flavor? 196. How much nutrients do fruits add to a ration? 197. Why is
it not right to determine the value of fruits entirely on the basis of
nutrients? 198. Give the general composition of apples? 199. What
compound is present to the greatest extent in the dry matter of apples?
200. How do apples differ in composition? 201. Give the general physical
composition of oranges. 202. What nutrients are present to the greatest
extent in oranges? 203. How do lemons differ in composition from
oranges? 204. How does grape fruit resemble and how differ in chemical
composition from oranges and lemons? 205. What are the main compounds in
strawberries? 206. In what ways are strawberries valuable in a ration?
207. Of what is grape juice mainly composed? 208. What acid is in
grapes, and what is its commercial value? 209. To what are the
differences in flavor and taste due? 210. How do ripe olives differ in
composition from green olives? 211. What is the food value of the olive?
212. What physiological property does olive oil have? 213. What is the
principal nutrient in peaches? 214. What compounds give flavor to
peaches? 215. Of what does the dry matter of plums mainly consist? 216.
How do plums differ in composition from many other fruits? 217. What are
prunes? What is their food value? 218. How do dried fruits differ in
composition from fresh fruits? 219. What should be the stage of ripeness
of fruit in order to secure the best results in canning? 220. How do
canned fruits differ in composition and nutritive value from fresh
fruits? 221. To what extent are metals dissolved by fruit juices? 222.
Why should tin in which canned goods are preserved be of good quality?
223. What preservatives are sometimes used in the preparation of canned
fruits? 224. What is the objection to their use? 225. Why are fruits
necessary in the ration? 226. What change does heat bring about in the
pectose substances of fruits?
CHAPTER V
SUGAR, MOLASSES, SIRUPS, HONEY, AND CONFECTIONS
227. What is sugar? 228. From what sources are sugars obtained? 229.
Name the two divisions into which sugars are divided. 230. How are
sugars graded commercially? 231. What per cent of purity has granulated
sugar? 232. How is the coloring material of sugar removed? 233. How is
sugar treated to make it whiter? 234. What value as a nutrient does
sugar possess? 235. Why should sugar be combined with other nutrients?
236. What foods contain appreciable amounts of sugar? 237. Why is an
excessive amount of sugar in a ration undesirable? 238. Does sugar
possess more than condimental value? 239. What is the average quantity
of sugar consumed in this country? 240. What is maple sugar? 241. How
does it differ in composition from other sugar? 242. How is adulterated
maple sugar detected? 243. To what extent is granulated sugar
adulterated? 244. Why is it not easily adulterated? 245. What are the
dextrose sugars? 246. How do they differ chemically from sucrose? 247.
What is the inversion of sugar? 248. In what way does acid act upon
sugar? 249. How are the acid products removed? 250. What is the food
value of glucose? 251. What is molasses? 252. How is it obtained? 253.
Of what is it composed? 254. What gives taste and flavor to molasses?
255. How may molasses act upon metalware? 256. What is the food value of
molasses? 257. What is sirup? 258. Name three kinds of sirup, and
mention materials from which they are prepared. 259. What is the
polariscope, and how is it employed in sugar work? 260. What is honey?
261. How does it differ in composition from sugar? 262. How is strained
honey adulterated? 263. What materials are used in the preparation of
confections? 264. What changes take place in their manufacture? 265.
What materials are used for imparting color? 266. What can you say in
regard to the coal tar colors? 267. What should be the position of candy
in the dietary? 268. What can you say of the comparative value of cane
and beet sugar? 269. How do the commercial grades of sugar compare as to
nutritive value? 270. What are some of the impurities in candy? 271.
What is saccharine? 272. What are its properties?
CHAPTER VI
LEGUMES AND NUTS
273. What nutrients do the legumes contain in comparatively large
amounts? 274. How does the amount of this nutrient compare with that
found in meats? 275. Why are legumes valuable crops in general farming
and for the feeding of farm animals? 276. Give the general composition
of beans. 277. How do beans compare in protein content with cereals?
278. How does the protein of beans differ from that of many other food
materials? 279. To what extent are the nutrients of beans digested? 280.
What influence does the combination of beans with other foods have upon
digestibility? 281. What influence does removal of skins have upon
digestibility? 282. In what part of the digestive tract are beans mainly
digested? 283. How does the cost of the nutrients in beans compare with
that of the nutrients in other foods? 284. How do string beans differ
from green beans? 285. Give the general composition, digestibility, and
nutritive value of peas. 286. What can you say of the use of copper
sulphate in the preparation of canned peas? 287. What nutrients do
peanuts contain in large amounts? 288. Give the general composition of
nuts. 289. What are the characteristics of pistachio? 290. Give the
general composition of the cocoanut. 291. What is cocoanut butter? 292.
To what extent may nuts contribute to the nutritive value of a ration?
CHAPTER VII
MILK AND DAIRY PRODUCTS
293. What can you say as to the importance of dairy products in the
dietary? 294. Give the general composition of milk. 295. What compound
in milk is most variable? 296. To what extent are the nutrients in milk
digestible? 297. What influence does milk have upon the digestibility of
other foods? 298. Why is cheese cured in cold storage? 299. How can the
tendency of a milk diet to produce costiveness be overcome? 300. Why is
it necessary to consider the sanitary condition of milk? 301. What
factors influence the sanitary condition of milk? 302. What is certified
milk? 303. What is pasteurized milk? 304. How can milk be pasteurized
for family use? 305. What is tyrotoxicon? 306. What is its source in
milk? 307. To what is the color of milk due? 308. To what extent is
color associated with fat content? 309. What causes souring of milk?
310. What change occurs in the milk sugar? 311. What are the most
favorable conditions for the souring of milk? 312. What are some of the
preservatives used in milk. 313. What objection is urged against their
use? 314. What is condensed milk? 315. What is buttermilk, and what
dietetic value has it? 316. How does goats' milk differ from cows' milk?
317. What is koumiss, and how is it prepared? 318. What are the prepared
milks? 319. How does human milk differ in composition from cows' milk?
320. Give the nutritive value of skim milk. 321. What content of fat
should cream contain? 322. In what ways is milk adulterated? 323. How
are these adulterations detected? 324. Give the general composition of
butter. 325. What is the maximum amount of water that a butter may
contain without being considered adulterated? 326. What can you say in
regard to the digestibility of butter? 327. How is butter adulterated?
328. How does oleomargarine compare in digestibility and food value with
butter? 329. What is the food value of butter? 330. How does cheese
differ in composition from butter? 331. Give the general composition of
cheese. 332. To what are the flavor and odor of cheese due? 333. Why is
cheese ripened? 334. What chemical changes take place during ripening?
335. To what extent are the nutrients of cheese digested? 336. Why is
cheese sometimes considered indigestible? 337. To what extent do the
nutrients of different kinds of cheese vary in digestibility? 338. How
does cheese compare in nutritive value and cost with meats? 339. What is
cottage cheese? 340. What is Roquefort cheese? 341. Name four kinds of
cheese, and say to what each owes its individuality. 342. How is cheese
adulterated? 343. Why are dairy products in older agricultural regions
generally cheaper than meats?
CHAPTER VIII
MEATS AND ANIMAL FOOD PRODUCTS
344. Give the general composition of meats. 345. How do meats differ in
chemical composition from vegetable foods? 346. What is the principal
non-nitrogenous compound of meats, and what of vegetables? 347. Name the
different classes of proteins in meats. 348. Which class is present in
largest amounts? 349. To what extent are amid compounds present in
meats? 350. What characteristics do amids impart to meats? 351. How are
alkaloids produced in meats? 352. In what ways does the lean meat of
different kinds of animals vary chemically and physically? 353. Give the
general composition of beef. 354. What relationship exists between the
fat and water content of beef? 355. How much refuse have meats? 356. In
what forms are the ash elements (mineral matter) present in meats? 357.
How does veal differ in composition from beef? 358. What general changes
in composition occur as animals mature? 359. How do these compare with
the changes that take place when plants ripen and seeds are produced?
360. How does mutton vary in composition from beef? 361. How does it
compare in food value with beef? 362. How do lamb and mutton differ in
composition? 363. To what extent do the various cuts differ in
composition? 364. How do the more expensive cuts of lamb compare in
nutritive value with the less expensive cuts? 365. How does pork differ
in composition from other meats? 366. Give the general composition of
ham. 367. Give the composition and nutritive value of bacon. 368. How
does bacon compare in food value with other meats? 369. How does the
character of the fat influence the composition and taste of the meat?
370. What influences the texture or toughness of meats? 371. How do
cooked meats compare in composition with raw meats? 372. To what extent
are nutrients lost in the boiling of meats? 373. What influence does the
temperature of the water in which the meat is placed for cooking have
upon the amount of nutrients extracted? 374. To what is the shrinking of
meats in cooking due? 375. Of what does meat extract mainly consist?
376. To what do beef extracts owe their flavor? 377. What is their food
value? 378. What is their dietetic value? 379. What is lard? 380. How
does it differ in composition from other fats? 381. What is imparted to
meats during the smoking process? 382. Why is saltpeter used in the
preservation of meats? 383. Do vegetable foods contain nitrates and
nitrites? 384. How does poultry resemble and how differ in composition
from other meat? 385. Give the characteristics of sound poultry. 386.
Give the general composition of fish. 387. How does the flesh of
different kinds of fish vary in composition? 388. What influence does
salting and preservation have upon composition? 389. How do fish and
meat compare in digestibility? 390. How does the mineral matter and
phosphate content of fish compare with that of other foods? 391. What
are the main nutrients in oysters? 392. Give the general food value of
oysters. 393. What is meant by the fattening of oysters? 394. What
effect does the character of the water used in fattening have upon the
sanitary value? 395. Give the general composition of the egg. 396. How
do different parts of the egg differ in composition? 397. How does the
egg differ in composition from the potato? 398. Is color an index to the
composition of the egg? 399. What effect does cooking have upon the
composition of the egg? 400. What factors influence the flavor of eggs?
401. How do different ways of cooking affect the digestibility? 402.
Under what conditions can eggs be used economically in the dietary? 403.
Why should eggs be purchased and sold by weight? 404. How do canned
meats differ in composition from fresh meats? 405. How do the nutrients
of canned meats compare in cost with those of fresh meat? 406. What are
the advantages of canned meats over fresh meats? 407. What are some of
the materials used in the preservation of meats?
CHAPTER IX
CEREALS
408. How are the cereals milled? 409. What are the cereals most commonly
used for food purposes? 410. Give the general composition of cereals as
a class. 411. What are the main nutrients in corn preparations? 412.
What influence does the more complete removal of the bran and germ of
corn have upon its digestibility? 413. How does the cost of nutrients in
corn compare with other foods? 414. Why is corn alone not suitable for
bread-making purposes? 415. Why should corn be combined in a ration with
foods mediumly rich in protein? 416. What change takes place in corn
meal from long storage? 417. Give the characteristics and composition of
oat preparations. 418. How does removal of the oat hull affect the
composition of the product? 419. To what extent do the various oat
preparations on the market differ in composition and food value? 420. Do
oats contain any special alkaloidal or stimulating principle? 421. Why
should oatmeal receive longer and more-thorough cooking than many other
foods? 422. To what extent are the nutrients in oatmeal digested? 423.
How do wheat preparations differ in general composition from corn and
oat preparations? 424. What influence upon the composition of the wheat
breakfast foods has partial or complete removal of the bran? 425. What
is the effect upon their digestibility and nutritive value? 426. What
are the special diabetic flours, and how are they prepared? 427. What
are the wheat middlings breakfast foods, and how do they compare in
digestibility and food value with bread? 428. How do they differ
mechanically? 429. How does barley differ from wheat in general
composition? 430. What is barley water, and what nutritive material does
it contain? 431. What cereal does rice resemble in composition? 432.
With what food materials should rice be combined to make a balanced
ration? 433. What can you say as to comparative ease and completeness
of digestibility of rice? 434. Why are cereals valuable in the ration?
435. In what way do they take a mechanical part in digestion? 436. What
are predigested breakfast foods? 437. How would you determine the
general nutritive value of a breakfast food, knowing the kind of cereal
from which it was prepared? 438. To what extent are cereals modified or
changed in composition by cooking? 439. To what extent are the nutrients
of cereal foods digested and absorbed by the body? 440. To what extent
do the cereals supply the body with mineral matter? 441. How does the
phosphate content of cereals compare with that of meats and milk?
CHAPTER X
WHEAT FLOUR
442. Why is wheat flour especially adapted to bread-making purposes?
443. To what extent may wheat vary in protein content? 444. What are
spring wheats? 445. What are winter wheats? 446. Give the general
characteristics of each. 447. What are glutinous wheats? 448. What are
starchy wheats? 449. Name the different proteids in wheat flour. 450.
About how much starch does wheat flour contain? 451. What other
carbohydrates are also present? 452. What is the roller process of flour
milling? 453. What is meant by the first break? 454. How are the
different products of the wheat kernel separated? 455. What is meant by
middlings flour? 456. What is break flour? 457. What is patent flour?
458. Name the high grade flours. 459. Name the low grade flours. 460.
How are the impurities removed from wheat flour? 461. What per cent of
the wheat kernel is returned as flour? As offals? 462. What becomes of
the wheat germ during milling? 463. What sized bolting cloths are used
in milling? 464. What is graham flour? 465. How does it differ in
mechanical and chemical composition from white flour? 466. What is
entire wheat flour? 467. How does it differ in physical and chemical
composition from white flour? 468. What effect has the refining of
flour upon the ash content? 469. How do low and high grade flours differ
in chemical composition? 470. How do the wheat offals differ in
composition from the flour? 471. What are the factors which influence
the composition of flours? 472. What effect does storage have upon the
bread-making value of flour? 473. What change takes place when new wheat
is stored in an elevator? 474. What is durum wheat flour, and how does
it differ from other flour? 475. What gives flour its color? 476. Why is
color an index of grade? 477. How is the color of a flour determined?
478. How do flours differ in granulation? 479. How does the granulation
affect the physical properties of flour? 480. How is the granulation of
flour approximately determined? 481. How is the absorptive capacity of a
flour determined? 482. What factors cause a variation in the capacity of
flours to absorb water? 483. Give the characteristics of a good gluten.
484. What causes unsound flours? 485. How is the bread-making value of a
flour determined? 486. How are flours bleached? 487. How does bleaching
affect the chemical composition of flour? 488. What influence does
bleaching have upon bread-making value? 489. Traces of what compounds
are formed during bleaching? 490. Are these compounds injurious to
health? 491. What effect does bleaching have upon the color of fiber and
débris particles in flour? 492. Is it possible to bleach low grade
flours and cause them to resemble high grade flours? 493. Are flours
usually adulterated? 494. Why? 495. How would mineral adulterants be
detected? 496. How would the presence of other cereals be detected? 497.
How does flour compare in nutritive value with other foods? 498. How
does the cost of flour compare with that of other foods? 499. What
causes flours to vary so in bread-making value? 500. Why may flours
produced from the same type of wheat vary slightly in character from
year to year? 501. What relationship exists between the nutritive and
bread-making value of a flour?
CHAPTER XI
BREAD AND BREAD MAKING
502. Define leavened and unleavened bread. 503. Why is yeast used in
bread making? 504. Give the characteristics of a good loaf of bread.
505. Why is flour used for bread making purposes? 506. Name the eight
chemical changes that take place during bread making. 507. To what
extent do losses in dry matter occur during bread making? 508. What
compounds suffer losses during bread making? 509. What is yeast? 510.
What chemical changes does it produce? 511. What becomes of these
products during bread making? 512. How is compressed yeast made? 513.
What part does the alcohol take in bread making? 514. What temperature
is reached in the interior of the loaf during bread making? 515. Through
what chemical changes does starch pass during bread making? 516. To what
extent are soluble carbohydrates formed? 517. In what way is starch
acted upon mechanically? 518. Explain the structure of the starch grains
in flour and in dough after they have been acted upon by the yeast
ferments. 519. To what extent are acids produced in bread making? 520.
What becomes of the acids formed? 521. How may the acids thus developed
affect the properties of other chemical compounds? 522. To what extent
are volatile carbon compounds, other than carbon dioxid and alcohol,
liberated during bread making? 523. What changes occur to the various
proteids during the process of bread making? 524. Why do flours vary in
quality of gluten? 525. To what extent do losses of nitrogen occur
during bread making? 526. How much of the total nitrogen of flour is
present as proteids? 527. How is the fat of flour affected during the
process of bread making? 528. What effect does the addition of 10 per
cent of wheat starch to flour have upon the size of the loaf? 529. What
effect does the addition of 10 per cent of wheat gluten to flour have
upon the size of the loaf? 530. What relationship exists between gluten
content and capacity of a flour to absorb water? 531. Give the general
composition of bread. 532. What factors influence its composition? 533.
What effect does the use of skim milk and lard in bread making have upon
composition? 534. How does the temperature of the flour influence the
bread-making process? 535. Why is it necessary to vary the process of
bread making in order to get the best results with different kinds of
flour? 536. To what extent are the nutrients of bread digested? 537. How
does graham bread compare in digestibility with white bread? 538. How do
graham and entire wheat breads compare in nutritive value with white
bread? 539. What value do graham and entire wheat breads have in the
dietary? 540. Why is white bread generally preferable in the dietary of
the laboring man? 541. How do graham and entire wheat flours compare in
chemical composition with white flour? 542. How do they compare in
mechanical composition? 543. To what is the difference in digestibility
supposed to be due? 544. Are graham and entire wheat breads necessary in
a ration as a source of mineral elements? 545. What is the main
difference in composition between old and new bread? 546. How do
different kinds of bread made from the same flour compare in composition
and nutritive value? 447. How does toast differ in composition from
bread? 548. What influence does toasting have upon digestibility? 549.
What is gained by toasting bread? 550. How does bread compare in
nutritive value with other cereal foods? 551. How does bread compare in
nutritive value with animal foods?
CHAPTER XII
BAKING POWDERS
552. What is a baking powder? 553. What are the two kinds of materials
which baking powders contain? 554. Name the different types of baking
powders. 555. How does baking powder differ in its action from yeast?
556. What are the cream of tartar baking powders? 557. What is the
nature of the residue which they leave? 558. What are the phosphate
baking powders? 559. What is the nature of the residue which they
leave? 560. Why is the mineral phosphate not considered equally valuable
with that naturally present in foods? 561. What are the alum baking
powders? 562. What residue is left from the alum powders? 563. Which of
the three classes of baking powders is considered the least
objectionable? 564. Why is a new baking powder preferable to one that
has been kept a long time? 565. Why should baking powders be kept in tin
cans, and not in paper? 566. Why are fillers used in the manufacture of
baking powders? 567. How may a baking powder be prepared at home? 568.
How does such a baking powder compare in cost and efficiency with those
purchased in the market?
CHAPTER XIII
VINEGARS, SPICES, AND CONDIMENTS
569. What is vinegar? 570. How is it made? 571. Give the three chemical
changes that take place in its preparation. 572. Why is air necessary in
the last stage of the process? 573. What ferments take part in the
production of vinegar? 574. What is malt vinegar? 575. What materials
other than apples can be used in the preparation of vinegar? 576. Give
the characteristics of a good vinegar. 577. In what ways are vinegars
adulterated? 578. What food value has vinegar? 579. Why should vinegars
not be stored in metalware? 580. What dietetic value has vinegar? 581.
To what materials do the spices owe their value? 582. What is pepper?
583. What is the difference between white and black pepper? 584. What
compounds give pepper its characteristics? 585. How are peppers
adulterated? 586. What is mustard? 587. Give its general composition.
588. How is it adulterated? 589. What is ginger? 590. How is it prepared
for the market? 591. Give its general composition. 592. What is
cinnamon? 593. What is cassia? 594. What gives these their taste and
flavor? 595. What are cloves? 596. How are they prepared? 597. What is
mace? 598. What is nutmeg? 599. Do the spices have any food value? 600.
What is their dietetic value? 601. Why is excessive use of some of the
spices objectionable?
CHAPTER XIV
TEA, COFFEE, CHOCOLATE, AND COCOA
602. What is tea? Name the two plants from which it is obtained, the
countries where each grows best, and the number of flushes each yields.
603. Upon what does the quality and grade of tea depend? 604. Give
differences in the preparation and composition of green and black teas.
605. The characteristic flavor of tea is imparted by what compound? 606.
To what compound are its peculiar physiological properties due? 607.
What can you say of the protein in tea as to amount and food value? 608.
Why should tea--especially green tea--be infused for a very short time,
never boiled? 609. What effect has tannin upon the digestion of
proteids? 610. What three points are considered in judging a tea? 611.
What is the most common form of tea adulteration? 612. Describe the
coffee plant and fruit, and its method of preparation for market. 613.
What is the difference in the chemical composition of tea and coffee?
614. Name the characteristic alkaloid of coffee. How does it compare
with theme? 615. Why may coffee not be considered a food? 616. Tell
different ways in which coffee may be adulterated. 617. Which is more
commonly practiced, tea or coffee adulteration? Why? 618. How may real
coffee be distinguished from chicory? Why? 619. Name the three kinds of
coffee in general use. Give distinguishing features of each. Which is
usually considered best? 620. From what are cocoa and chocolate
obtained? 621. Give the two methods of preparing cocoa. 622. What
alkaloid similar to the theme and caffeine of tea and coffee is present
in cocoa and chocolate? 623. What is the difference in preparation of
cocoa and chocolate? 624. What are cereal coffee-substitutes? 625. What
nutritive value have they? 626. How do they differ in composition from
coffee? 627. To what extent does cocoa add to the nutritive value of a
ration? 628. What is plain chocolate? 629. Why do chocolate preparations
vary so widely in composition? 630. What treatment is given to the cocoa
bean in its preparation for commerce? 631. What treatment is sometimes
given to prevent separation of the cocoa fat? 632. In what ways may
cocoa and chocolate preparations be adulterated?
CHAPTER XV
DIGESTIBILITY OF FOODS
633. Define the term nutrient. 634. Do all the nutrients of food have
the same degree of digestibility? 635. What is a digestion coefficient?
636. How is the digestibility of a food determined? 637. What volatile
products are formed during the digestion of food? 638. Define digestible
protein; digestible carbohydrates, digestible fat. 639. What is the
available energy of a ration? 640. How is it determined? 641. How do the
nutrients, protein, fat, and carbohydrates, compare as to available
energy? 642. Why is it necessary to consider the caloric value of a
ration? 643. Is the protein molecule as completely oxidized in the body
as starch or fat? 644. What residue is left from the digestion of
protein? 645. What part do the soluble ferments take in digestion? 646.
To what extent are the nutrients of animal foods digested? 647. Which
nutrient, protein or fat, is the most completely digested? 648. How do
vegetable foods compare in digestibility with animal foods? 649. What
effect does cellulose have upon digestibility? 650. Which of the
nutrients of vegetables, protein or carbohydrates, is more completely
digested? 651. What mechanical value may cellulose have in a ration?
652. Why must bulk be considered in a ration, as well as nutrient
content? 653. Name the eight most important factors influencing the
digestibility of foods. 654. To what extent does the combination of
foods affect the digestibility of the nutrients? 655. Why does a mixed
ration give better results than when only a single food is used? 656.
How does the amount consumed affect the completeness of the digestive
process? 657. To what extent does the method of preparing food affect
digestibility? 658. What is gained, so far as digestibility is
concerned, by the cooking of foods? 659. To what extent does the
mechanical condition of food affect its digestibility? 660. Why is it
desirable to have some coarsely granulated foods in a ration? 661. Why
should the ration not be composed exclusively of finely granulated
foods? 662. Why is some coarsely granulated food more essential in the
dietary of the sedentary than in the dietary of the laborer? 663. How
does palatability affect the digestive process? 664. Do psychological
processes in any way affect digestion? 665. What physiological
properties do some foods possess? 666. To what are these physiological
properties due? 667. To what extent is individuality a factor in
digestion? 668. To what extent does digestibility differ with
individuals? 669. Why do some foods affect individuals in different
ways? 670. Why is it necessary that the quantity, quality, and character
of the food should vary with different individuals? 671. In what
different ways is the expression "digestibility of a food" used? 672.
Why is it necessary to consider the digestibility of food, as well as
its composition? 673. Does the digestibility of a food necessarily
indicate the economic uses that will be made of it by the body? 674. How
is it possible for one food containing 10 per cent of digestible
protein, and other nutrients in like amounts, to be more valuable than
another food with the same per cent of digestible protein and other
nutrients? 675. How is it possible for one food to contain less total
protein than another food and yet be more valuable from a nutritive
point of view? 676. Why is it necessary to consider the mechanical
condition of a food and its combination with other foods, as well as its
chemical composition? 677. What effect does lack of a good supply of air
have upon the completeness of the digestion process? 678. In what ways
does the digestion of food resemble the combustion of fuel? 679. What is
gained by a study of the digestibility of foods? 680. Why may two foods
of the same general character give different results when used for
nutritive purposes?
CHAPTER XVI
COMPARATIVE COST AND VALUE OF FOODS
681. To what extent do the nutritive value and the market price of foods
vary? 682. How is the value of one food expressed in terms of another
food? 683. How determine the amount of nutrients that can be procured in
a food for a given sum of money? 684. How compare the amounts of
nutrients that can be procured in two foods for a given sum of money?
685. How is it possible to determine approximately which of two foods is
cheaper, when the price and composition of the foods are known? 686. To
what nutrient is preference usually given in assigning a value to a
food? 687. When the difference in this nutrient between two foods is
small, then the preference is given to what nutrients? 688. At ordinary
prices, what are the cheapest vegetable foods? 689. What are among the
cheapest animal foods? 690. Why is it not possible to determine the
value of a food absolutely from its composition and digestibility? 691.
Why is it necessary to consider the physical as well as the chemical
composition of foods? 692. What proportion of the income of the laboring
man is usually expended for food? 693. What are the most expensive
foods? 694. What foods furnish the largest amount of nutrients at the
least cost?
CHAPTER XVII
DIETARY STUDIES
695. What is a dietary study? 696. How is a dietary study made? 697.
What is the value of the dietary study of a family? 698. To what extent
does the protein in the dietary range? 699. Why is a scant amount of
protein in a ration undesirable? 700. Why is an excess of protein in the
ration undesirable? 701. What are dietary standards? 702. How are such
standards obtained? 703. Why is it desirable in a ration to secure the
protein and other nutrients from a variety rather than from a few foods?
704. Why is it necessary to consider the caloric value of a ration? 705.
How is this determined? 706. What is a wide nutritive ratio? 707. What
is a narrow nutritive ratio? 708. Why should the amount of nutrients
consumed vary with the work performed? 709. How should the nutrients be
apportioned among the meals? 710. What are some of the most common
dietary errors? 711. What analogy exists between human and animal
feeding? 712. What is gained by the rational feeding of both humans and
animals? 713. What use can be made of the results of dietary studies for
improvement of the dietary? 714. Why is it not possible for animal foods
to compete in economy with cereal and vegetable foods? 715. Is a
well-balanced ration and one containing an ample supply of nutrients
necessarily an expensive ration? 716. Show how it is possible for one
family to spend less money for food than another family, and yet secure
more digestible nutrients and energy. 717. What are some of the most
erroneous ideas as to food values? 718. Why is it necessary to consider
previously acquired food habits in the selection of foods? 719. In
general, what portion of the nutrients of a ration should be derived
from vegetable foods, and what portion from meats? 720. To what extent
may a ration vary from the dietary standards? 721. Why are some
inexpensive foods often expensive when prepared for the table? 722. What
are some of the ways in which the cost of a ration can be decreased
without sacrificing nutritive value? 723. Why do different nationalities
acquire distinct food habits? 724. Why is it not possible to make sudden
and radical changes in the dietary? 725. Why is it not possible for a
dietary which gives ample satisfaction for one class of people to be
applied to another class with equal satisfaction? 726. What relationship
exists between the dietary of a nation and its physical development?
727. What relationship exists between dietary habits and mental
development and vigor? 728. Why is it unnecessary and undesirable to
regulate absolutely the amount of nutrients consumed in the daily
ration? 729. What is the general tendency as to quantity of food and
amount of nutrients consumed? 730. Why do people of sedentary habits
require a different dietary from those pursuing active, out-of-door
occupations?
CHAPTER XVIII
RATIONAL FEEDING OF MAN
731. What is the object of the rational feeding of man? 732. On what is
it based? 733. How does it compare with the rational feeding of animals?
734. What is a standard ration? 735. How is it determined? 736. To what
extent may the nutrients of a ration vary from the standard? 737. How do
you combine foods to form a balanced ration? 738. What foods are
valuable for supplying protein? 739. What foods supply fats? 740. What
foods are rich in carbohydrates? 741. What other requisites should a
ration have in addition to supplying the necessary nutrients? 742. Why
is it necessary to consider the calorie value of a ration? 743. If a
ration contained an excess of carbohydrates and a scant amount of
protein, how could it be improved? 744. How do you calculate the
nutrients in a fraction of a pound of food? 745. Give the amounts of the
common food materials, as potatoes, bread, butter, milk, and cheese,
ordinarily combined to form a ration. 746. To what extent may foods
differ in composition from the average analysis given? 747. What foods
are subject to the greatest and what foods to the least variation?
CHAPTER XIX
WATER
748. Why is water regarded as a food? 749. Does it enter chemically into
the composition of plants? Of animals? 750. In addition to serving as a
food, why is water necessary for life processes? 751. In what ways may
water be improved? 752. What are the most common forms of impurities?
753. What are the mineral impurities of water? 754. What is their
source? 755. What effect do some of these minerals have upon the value
of the water? 756. What causes some waters to dissolve limestone? 757.
What are permanently hard waters? 758. To what is temporary hardness in
water due? 759. What is the best way to remove mineral matter from
water? 760. What are the organic impurities of water? 761. What are the
sources of the organic impurities? 762. What change does the organic
matter of water undergo? 763. What becomes of the nitrogen of the
organic matter? 764. What does the presence of nitrates in water
indicate? Nitrites? 765. What is the total solid matter of a water, and
how is it obtained? 766. Define the terms free ammonia; albuminoid
ammonia. 767. What does the presence of chlorine in a surface well water
indicate? 768. Explain natural purification of water. 769. Can natural
purification always be relied upon? 770. Why does the character of the
drinking water affect health? 771. What diseases are mainly caused by
impure drinking water? 772. With what materials in water are the
disease-producing organisms associated? 773. Why should a water of
questionable purity be boiled? 774. State how the boiling should be
done, to be effective. 775. Why should boiled water receive further care
in its storage? 776. What effect does improvement of the water supply of
a city have upon the death rate? 777. How may connections between
cesspools and surface well waters be traced? 778. What impurities do
rain waters contain? 779. Explain the workings of the Pasteur and
Berkefeld water filters. 780. Why must special attention be given to
cleaning the water filter? 781. Explain the processes employed for the
removal of mechanical impurities of water by sedimentation and the use
of chemicals. 782. Why should such purification be under the supervision
of a chemist or bacteriologist? 783. What effect does freezing have upon
the purity of water? 784. Why are precautions necessary in the use of
ice for refrigeration? 785. What are mineral waters? 786. How are
artificial mineral waters prepared? 787. What are the more common
materials used in their preparation? 788. Why should mineral waters be
extensively used only by the advice of a physician? 789. What are some
of the materials used for softening water? 790. Which are the least
objectionable of these materials? 791. Which are the most objectionable?
792. What can you say of the use of ammonia and ammonium carbonate for
softening waters? 793. In washing clothing after contagious diseases,
what materials may be used for disinfecting? 794. Why, in softening
waters for household purposes, must caustic soda, potash, and bleaching
powder be used with caution? 795. Why is it necessary to determine by
trial the material most suitable for softening water? 796. What
advantage, from a pecuniary point of view, results from the improvement
of the water supply of a community?
CHAPTER XX
FOOD IN ITS RELATION TO HOUSEHOLD SANITATION AND STORAGE
797. What are the compounds usually determined in a food analysis? 798.
Does such an analysis necessarily indicate the presence of injurious
compounds? 799. What are the sources of the injurious organic compounds
in foods? 800. Why is it necessary to consider sanitary condition as
well as chemical composition? 801. What are the sources of contamination
of foods? 802. What is the object of the sanitary inspection of food?
803. How may flies carry germ diseases? 804. Why should food be
protected from impure air and dust particles? 805. Why should places
where vegetables are stored be well ventilated? 806. How may the dirt
adhering to vegetables be the carrier of germ diseases? 807. Why should
the cellar in which food is stored be in a sanitary condition? 808. What
effect does the cleaning of streets and improvement of the sanitation of
cities have upon the death rate? 809. Name the three natural
disinfectants, and explain the action of each. 810. Why must dishes and
utensils in which foods are placed be thoroughly cleaned? 811. Explain
the principle of refrigeration. 812. What kind of ferment action may
take place at a low temperature? 813. Why is some ventilation necessary
in refrigeration? 814. What effect does refrigeration have upon the
composition of food? 815. What relationship exists between unsanitary
condition of soils about dwellings and contamination of the food? 816.
Why should special attention be given to the sanitary disposal of
kitchen refuse? 817. Name the ways in which this can be accomplished.
818. How may foods become contaminated through imperfect plumbing? 819.
Mention the conditions necessary in order to keep foods sanitary.
REFERENCES
The following list of references is given for the use of the student in
case additional information is desired upon some of the subjects
discussed in this work. The list is not intended as a complete
bibliography of the subject of foods. The advanced student will find
extended references in the Experiment Station Record and the various
chemical, physiological, and bacteriological journals.
1. SNYDER: The Chemistry of Plant and Animal Life.
2. Minnesota Experiment Station Bulletin No. 54: Human Food
Investigations.
3. CROSS AND BEVANS: Cellulose.
4. WILEY: Principles and Practice of Agricultural Analysis,
Vol. III.
5. Minnesota Experiment Station Bulletin No. 74: Human Food
Investigations.
6. PARRY: The Chemistry of Essential Oils, etc.
7. U. S. Department of Agriculture, Farmers' Bulletin No. 142:
Principles of Nutrition and Nutritive Value of Food.
8. MANN: Chemistry of the Proteids.
9. Minnesota Experiment Station Bulletin No. 85: Wheat and Flour
Investigations.
10. ARMSBY: Principles of Animal Nutrition.
11. SHERMAN: Organic Analysis.
12. U. S. Department of Agriculture, Office of Experiment Stations
Bulletin No. 43: Digestion Experiments with Potatoes and Eggs.
13. Unpublished results of author.
14. U. S. Department of Agriculture, Bureau of Animal Industry Bulletin
No. 49: Cold Curing of Cheese.
15. WILEY: Foods and Their Adulteration.
16. Minnesota Experiment Station Bulletin No. 63: Miscellaneous
Analyses.
17. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No.
13, Part 8: Canned Vegetables.
18. LEACH: Food Inspection and Analysis.
19. U. S. Department of Agriculture, Farmers' Bulletin No. 256:
Preparation of Vegetables for the Table.
20. U. S. Department of Agriculture Year Book, 1905: Fruit and its Uses
as Food.
21. Handbook of Experiment Station Work, 1893.
22. U. S. Department of Agriculture, Division of Chemistry Bulletin No.
94: Studies on Apples.
23. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No.
69: Fruits and Fruit Products.
24. U. S. Department of Agriculture, Farmers' Bulletin No. 203: Canned
Fruits, Preserves, and Jellies.
25. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No.
27: Sugar Beet Industry.
26. SADTLER: A Handbook of Industrial Organic Chemistry.
27. Minnesota Experiment Station Bulletin No. 86: The Food Value of
Sugar. The Digestive Action of Milk.
28. HUTCHISON: Food and Principles of Dietetics.
29. U. S. Department of Agriculture, Farmers' Bulletin No 93: Sugar as
Food.
30. U. S. Department of Agriculture, Office of Experiment Stations
Bulletin No. 252: Maple Sugar and Sirup.
31. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No.
13, Part 6: Sugar, Molasses, Sirup, and Confections.
32. U. S. Department of Agriculture, Farmers' Bulletin No. 121: Peas and
Beans as Food.
33. U. S. Department of Agriculture, Farmers' Bulletin No. 122: Nuts as
Food.
34. Maine Experiment Station Bulletin No. 54: Nuts as Food.
35. California Experiment Station Bulletins Nos. 107 and 132:
Investigations among Fruitarians.
36. U. S. Department of Agriculture, Farmers' Bulletin No. 74: Milk as
Food.
37. U. S. Department of Agriculture, Farmers' Bulletin No. 63: Care of
Milk on the Farm.
38. U. S. Department of Agriculture, Farmers' Bulletin No. 149:
Digestibility of Milk.
39. RUSSELL: Dairy Bacteriology.
40. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No.
13. Part 1: Dairy Products.
41. U. S. Department of Agriculture, Farmers' Bulletin No. 131:
Household Tests for Detection of Oleomargarine and Renovated Butter.
42. U. S. Department of Agriculture, Bureau of Animal Industry Bulletin
No 61: Relation of Bacteria to Flavor of Cheddar Cheese.
43. Minnesota Experiment Station Bulletin No. 92: The Digestibility and
Nutritive Value of Cottage Cheese, etc.
44. LAWES AND GILBERT: Experiments with Animals.
45. U. S. Department of Agriculture, Farmers' Bulletin No. 34: Meats,
Composition and Cooking.
46. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No.
13, Part 7: Lard and Lard Adulterants.
47. U. S. Department of Agriculture, Office of Experiment Stations
Bulletin No. 193: Cooking of Meats as Affecting Digestibility.
48. U.S. Department of Agriculture, Office of Experiment Stations
Bulletin No. 141: Experiments on Losses in Cooking Meats. See also
Office of Experiment Stations Bulletin No. 102: Losses in Cooking Meats.
49. U. S. Department of Agriculture, Office of Experiment Stations
Bulletin No. 66: Physiological Effect of Creatin and Creatinin.
50. U. S. Department of Agriculture, Office of Experiment Stations
Bulletin No. 162: The Influence of Cooking upon the Nutritive Value of
Meats.
51. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No.
13, Part 10: Preserved Meats.
52. RICHARDSON, W. D., Journal of the American Chemical
Society, December, 1907: The Occurrence of Nitrates in Vegetable Foods,
in Cured Meats, and Elsewhere.
53. U. S. Department of Agriculture, Office of Experiment Stations
Bulletin No. 182: Poultry as Food.
54. U. S. Department of Agriculture, Farmers' Bulletin No. 85: Fish as
Food.
55. U. S. Department of Agriculture, Farmers' Bulletin, Experiment
Station Work: Digestibility of Fish and Poultry.
56. U. S. Department of Agriculture, Farmers' Bulletin No. 249: Cereal
Breakfast Foods.
57. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No.
50: Composition of Maize.
58. U. S. Department of Agriculture, Office of Experiment Stations
Bulletin No. 305: Gluten Flour and Similar Foods.
59. HAMMERSTON: Physiological Chemistry.
60. EDGAR: The Wheat Berry.
61. Minnesota Experiment Station Bulletin No. 90: Composition and Value
of Grains.
62. U. S. Department of Agriculture, Office of Experiment Stations
Bulletin No. 101: Bread and Bread Making.
63. U. S. Department of Agriculture, Office of Experiment Stations
Bulletin No. 156: Digestibility and Nutritive Value of Bread and
Macaroni Flour.
64. U. S. Department of Agriculture, Office of Experiment Stations
Bulletin No. 67: Bread and Bread Making.
65. University of Nebraska Bulletin No. 102: The Effect of Bleaching
upon the Quality of Wheat Flour.
66. SNYDER: Wheat Flour and Bread.
67. U. S. Department of Agriculture, Office of Experiment Stations
Bulletin No. 126: Bread and Bread Making.
68. LAWES AND GILBERT: Experiments on Some Points in the
Composition of the Wheat Grain, of the Product in the Mill and Bread.
69. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No.
13, Part 5: Baking Powders.
70. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No.
13, Part 2: Spices and Condiments.
71. Food Standards: U. S. Department of Agriculture. See Annual Reports
of the Association of Official Agricultural Chemists.
72. U. S. Department of Agriculture, Office of Experiment Stations
Bulletin No. 21: Methods and Results of Investigations on the Chemistry
and Economy of Foods.
73. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No.
13, Part 7: Tea, Coffee, and Cocoa Preparations.
74. The Respiration Calorimeter: Year-book U. S. Department of
Agriculture, 1904.
75. Year Book U. S. Department of Agriculture, 1902: Cost of Food as
Related to its Nutritive Value.
76. See U. S. Department of Agriculture, Office of Experiment Stations
Bulletins Nos. 82, 71, 129, 116, 37, 55, 150. See also other bulletins
of the Office of Experiment Stations.
77. CHITTENDEN: Physiological Economy in Nutrition.
78. U. S. Department of Agriculture, Office of Experiment Stations
Bulletin No. 98: Effect of Severe and Prolonged Muscular Work on Food
Consumption.
79. HENRY: Feeds and Feeding.
80. U. S. Department of Agriculture, Office of Experiment Stations:
Dietary Studies in Chicago Bulletin No. 55.
81. U. S. Department of Agriculture, Office of Experiment Stations
Bulletin No. 116: Dietary Studies in New York City.
82. U. S. Department of Agriculture, Farmers' Bulletin No. 119: Banana
Flour.
83. U. S. Department of Agriculture, Office of Experiment Stations
Bulletin No. 159: Digest of Japanese Investigations on the Nutrition of
Man.
84. U. S. Department of Agriculture, Office of Experiment Stations
Bulletin No. 150: Dietary Studies at the Government Hospital for the
Insane, Washington, D.C.
85. U. S. Department of Agriculture, Office of Experiment Stations
Bulletin No. 149: Studies on the Food of Maine Lumbermen.
86. U. S. Department of Agriculture, Office of Experiment Stations
Bulletin No. 143: Studies on the Digestibility and Nutritive Value of
Bread at the Maine Experiment Station.
87. U. S. Department of Agriculture, Office of Experiment Stations,
Experiment Station Work, Vol. III: Wells and Pure Water.
88. U. S. Department of Agriculture, Farmers' Bulletin No. 88: Pure
Water on the Farm.
89 Mineral Impurities in Water. See various bulletins of the California
and New Mexico Agricultural Experiment Stations.
90. MASON: Examination of Water.
91. Department of the Interior, U. S. Geological Survey: The Quality of
Surface Waters in Minnesota.
92. FUERTES: Water and Public Health.
93. U. S. Department of Agriculture, Farmers' Bulletin No. 124:
Distilled Drinking Water.
94. TURNEAURE AND RUSSELL: Public Water Supplies.
95. VAUGHAN AND NOVY: Ptomains and Lencomains.
96. U. S. Department of Agriculture, Bureau of Entomology, Circular No.
71: House Flies.
97. ELLEN H. RICHARDS AND S. MARIA ELLIOTT: The Chemistry of
Cooking and Cleaning.
98. Dr. WOODS HUTCHINSON, _Saturday Evening Post_, 1908: The
Real Angels of the House.
99. HARRINGTON: Practical Hygiene.
100. PRICE: Handbook of Sanitation.
INDEX
Air, infection from impure, 287.
pure, disinfectant, 290.
Albuminoids, 23.
Alkaloids, 24.
Allspice, 202.
Almonds, 77.
Alum baking powder, 188.
Amids and Amines, 23.
Animal and vegetable foods, economy of, 250.
Animal foods, digestibility of, 220.
Apparatus used in experiments, 301.
Apples, 49.
pectose from, 307.
Ash, of foods, 4.
elements of plants, 5.
Asparagus, 43.
Available energy, 217.
nutrients, 216.
Bacteria in food, 32.
Baking powder, composition of, 186.
cream of tartar, 187.
phosphates, 189.
alum, 189.
inspection of, 191.
fillers, 191.
home-made, 191.
testing for alum, 315.
testing for ammonia, 316.
testing for phosphoric acid, 316.
Baking tests, 153-314.
Barley preparations, 128.
Beans, composition, 71.
digestibility, 72.
removal of skins, 72.
string, 73.
use of, in dietary, 74.
Beef, 101.
extracts, 110.
Beets, 41.
Beverages, composition, 213.
Bleaching of flour, 155.
Bolting cloth, 138.
Bread and bread making, 158-185.
leavened and unleavened bread, 158.
chemical changes during making, 159.
losses during bread making, 160.
production of carbon dioxide, 163.
production of alcohol, 163.
production of soluble carbohydrates, 165.
production of acids, 166.
production of volatile compounds, 167.
production of volatile nitrogenous compounds, 172.
wheat proteids, part taken by, 169.
oxidation of fat, 173.
starch, influence of, addition of, 173.
composition of bread, 174.
temperature of flour, 176.
use of skim milk, 176.
process of bread making, 177.
digestibility of bread, 178.
graham bread, use in the dietary, 179.
white and graham bread compared, 180.
mineral content of, 182.
new and old, 183.
action of heat on, 184.
different kinds of, 184.
Breakfast foods, 121-132.
Broth, 109.
Butter, composition, 91.
digestibility, 91.
adulteration, 92.
coloring, 92.
renovated, 92.
water in, 305.
Buttermilk, 88.
Cabbage, 41.
Candies, 69.
Canned meats, 118.
vegetables, 46.
peas, 75.
Carbohydrates defined, 8.
Carrots, 40.
Cauliflower, 41.
Cellars, storage of food in, 283.
Cellulose and properties, 8.
Cereals, 121-132.
preparation of, 121.
cost of, 121.
value of, 131.
use of, in dietary, 131.
corn preparations, 122.
oat preparations, 124.
wheat preparations, 126.
barley preparations, 128.
rice preparations, 129.
predigested, 130.
phosphates in, 131.
mineral matters of, 131.
coffees, 210.
Cesspools, 289.
Cheese, 92-96.
general composition, 92.
digestibility, 93.
use of, in dietary, 94.
cottage, 95.
different kinds of, 95.
adulteration, 96.
Chemical changes during cooking, 27-30.
Chemicals, use of, in preparation of foods permitted, 36.
Chestnuts, 76.
Chicory, detection in coffee, 319.
Chocolate, 212.
adulteration of, 213.
Cinnamon and cassia, 201.
Cloves, 201.
Coal tar dyes, testing for, 308.
Cocoa, 210.
Cocoanuts, 77.
Coffee, composition of, 207.
detection of chicory in, 319.
glazing of, 208.
substitutes, cereal, 210.
types of, 209.
Combustion of foods, 6.
Cooking, changes during, 27.
chemical, 27-30.
physical, 30-32.
bacteriological, 32.
Corn, sweet, 41.
preparations, 122.
Cream, 87.
Cream of tartar, 187.
Crude fiber of foods, 9.
Crude protein, 21.
Cucumbers, 42.
Dairy products, 80-97.
use of, in dietary, 96.
Dextrose, 64.
Dietary standards, 245.
Dietary studies, 244-260.
object of, 244.
mixed, desirable, 250.
of families compared, 253.
in public institutions, 259.
Digestibility of foods, 214.
of animal foods, 220.
of vegetable foods, 222.
Digestion, combination of foods, 223.
factors influencing, 223.
amount of food, 224.
method of preparation of food, 225.
mechanical condition of foods, 226.
psychological factors, 230.
individuality, 229.
Digestion and health, 219.
Dishcloth, unclean, 292.
Disinfectants, 281, 289, 295.
Drying of foods, 2.
Dry matter, 2.
Egg plant, 44.
Eggs, 114-118.
composition, 114.
digestibility, 116.
cooking of, 116.
use of, in dietary, 117.
Elements in foods, 7.
Energy, available, 217.
Energy value of rations, 246.
Entire wheat, 145.
Essential oils, 15.
occurrence, 15.
composition of, 16.
food value, 16.
Esthetic value of foods, 36.
Fat, occurrence in food, 12.
composition, 13.
physical properties, 14.
food value, 14.
individual fats, 14.
oxidation of, during bread making, 173.
Ferments, soluble, 34.
insoluble, 34.
Figs, 54.
Fish, 113.
Flavoring extracts, 56.
Flavors, composition of, 48.
occurrence of, 49.
food value, 49.
Flies, contamination of food by, 286, 295.
Foods, 215.
digestibility of, 215.
mechanical condition of, 226.
palatability of, 228.
physiological properties of, 228.
ash of, 4.
predigested, 130.
sodium chloride in, 4.
cost of, 231.
market price and nutritive value, 231-234.
composition of, 234-263.
comparative nutritive value, 231.
economy of production, 250.
habits, 250.
notions, 252.
relation to mental and physical vigor, 258.
amount consumed, 262.
injurious compounds in, 284.
contamination of, 284, 292.
sanitary inspection of, 286.
storage in cellars, 288.
infection from impure air, 287.
utensils for storage, 291.
raw, 27.
cheap and expensive, 252.
Fruits, composition of, 48.
canned, 54.
dried, 54.
canned and adulterated, 55.
Fruit extracts, 56.
Fruit flavors, 55.
Ginger, 200.
Gliadin, 314.
Gluten, addition of, to flour, 173.
moist and dry, 314.
Gluten properties of flour, 151.
Graham bread, 179.
use in dietary, 180.
Graham flour, 144.
Grape fruit, 51.
Grapes, 53.
Heat, action on foods, 30.
Hickory nuts, 77.
Honey, 68.
Ice, 279.
Inspection of food, 286.
Inversion of sugar, 64.
Kitchen refuse, 294.
Koumiss, 88.
Laboratory practice, 299.
Lard, 106.
substitutes, 107.
Legumes, 71-76.
Lemon extract, testing, 307.
Lemons, 51.
acidity of, 305.
Lettuce, 42.
Macaroni flour, 148.
Mace, 202.
Malted foods, 121.
Maple sugar, 62.
Meals, number of, per day, 248.
Measuring, directions for, 302.
Meat broth, 109.
Meats, 98-120.
general composition, 98.
proteids of, 99.
fat of, 100.
water of, 98.
texture of, 107.
cooking of, influence of, on composition, 108.
extractive materials, 110.
smoked, 111.
boric acid in, 312.
saltpeter in, 111.
canned, 118.
Melons, 43.
Microscope, use of, 304.
Milk, importance in dietary, 80.
general composition, 80.
souring of, 86.
condensed, 87.
digestibility, 81.
sanitary condition, 82.
certified milk, 84.
pasteurized, 84.
color of, 85.
preservatives in, 86.
goat's, 88.
human, 89.
adulteration of, 89.
prepared, 88.
formaldehyde in, 310.
Mineral matter, 4.
in ration, 5.
Mineral waters, 279.
Miscellaneous compounds, 16.
Mixed nitrogenous compounds, 25.
Mixed non-nitrogenous compounds, 16.
Moisture content of foods, variations in, 1.
Moisture in foods, how determined, 2.
Molasses, 65.
Mustard, 199.
testing for turmeric, 318.
Mutton, 103.
Nitrates in foods, 45.
Nitrites in foods, 111.
Nitrogen free extract, 11.
defined, 11.
composition, 12.
how determined, 12.
variable character of, 12.
Nitrogenous compounds, 17.
general composition, 17.
Non-nitrogenous compounds, classification of, 7.
Nutmeg, 202.
Nutrients, available, 216.
Nutritive value of nitrogenous compounds, 16.
starch, 9.
sugar, 11.
nitrogen free extract, 11.
fat, 12.
protein, 19.
amids, 23.
Nuts, 76-79.
use of, in dietary, 78.
Oat preparations, 124.
Oleomargarine, 92.
detecting, 310.
Olive oil, testing, 308.
Olives, 54.
Onions, 42.
Oranges, 50.
Organic acids, 15.
occurrence in foods, 15.
influence on digestion, 15.
use in plant economy, 15.
production during germination, 15.
Organic compounds, classification of, 7.
Organic matter, 6.
Oysters, 114.
Palatability of food, 228.
Parsnips, 40.
Peaches, 53.
Peanuts, 76.
fat from, 309.
Peas, 74.
canned, 75.
Pectose substances, 11.
Pepper, 198.
Phosphate baking powders, 189.
Physical changes during cooking, 30.
Physiological properties of foods, 228.
Pistachio, 77.
Plumbing, sanitary, 297.
Plums, 53.
Pork, 104.
Potatoes, 37.
composition, 39.
digestibility, 38.
nutritive value, 38.
sweet, 39.
Poultry, 112.
Predigested foods, 130.
Protein, composition of, 19.
properties of, 19.
combinations of, 20.
types of, 20.
crude, 21.
food value of, 22.
amount of, in ration, 246.
Psychological factors in digestion, 230.
Pumpkins, 45.
Rational feeding of man, 261-267.
Rations, wide and narrow, 245.
standard, 261.
object of, 261.
examples of, 264.
requisites of, 266.
protein requirements of, 246.
energy value of, 246.
References, 350.
Refrigeration, 292.
Refuse, disposal of, 294.
Renovated butter, 92.
Review questions, 323.
Rice preparations, 129.
Saccharine, 70.
Saltpeter in meats, 111.
Sanitary condition of vegetables, 45.
Sanitary inspection of food, 286.
Sausage, 111.
Sodium chloride in foods, 5.
Soil, sanitary condition of, 294.
Spices, 212.
Spinach, 42.
Squash, 45.
Starch, 9.
occurrence, 9.
composition, 9.
properties, 10.
food value, 10.
influence of heat on, 10.
Strawberries, 52.
Sugar, defined, 11.
beet, 58.
cane, 58.
commercial grades, 58.
manufacture of, 59.
sulphur in, 59.
digestibility of, 59.
value of, in dietary, 61.
adulteration of, 63.
maple, 62.
dextrose, 64.
Sunlight as a disinfectant, 290.
Sweet potatoes, 39.
Syrups, 66.
sorghum, 66.
Tea, 203-206.
black, 203.
green, 204.
composition of, 214.
judging of, 205.
adulteration of, 206.
physiological properties of, 206.
examination of leaves, 318.
Toast, 184.
Tomatoes, 43.
Underfed families, 251.
Vanilla extract, testing, 307.
Veal, 102.
Vegetable foods, 222.
Vegetables, 37-47.
edible portion, 47.
canned, 46.
sanitary condition of, 45.
digestibility of, 222.
Vinegar, 193-197.
preparation of, 193.
different kinds of, 195.
adulteration of, 196.
solids, 316.
specific gravity, 317.
acidity, 317.
Volatile matter, 6.
Water, drinking, 268-283.
importance, 268.
impurities in, 269.
mineral impurities, 270.
organic impurities, 271.
purification of, 272-278.
analysis, 271.
and typhoid fever, 273.
improvement of, 276.
boiling of, 276.
filtration of, 277.
distillation of, 278.
materials for softening water, 280.
testing purity of, 320.
Water in foods, 1.
how determined, 1.
Water supply, economic value, 282.
Waters, mineral, 279.
Weighing, directions for, 302.
Wheat cereal preparations, 126.
Wheat flour, 133.
spring and winter wheat flour, 133.
starchy and glutenous, 135.
composition of, 136.
process of milling, 136-140.
patent, 142.
grades of, 142.
composition of, 143.
ash content, 145.
graham, 145.
entire wheat, 145.
by-products, 146.
aging and curing, 147.
macaroni, 148.
color, 148.
granulation, 149.
capacity to absorb water, 150.
gluten, properties of, 151.
unsoundness of, 152.
baking tests, 153.
bleaching of, 155.
adulteration of, 156.
nutritive value of, 157.
water in, 304.
ash in, 305.
acidity of, 313.
moist and dry gluten, 314.
Yeast, action of, 161.
compressed, 162.
dry, 163.
BY HARRY SNYDER, B.S.
Professor of Agricultural Chemistry, University of Minnesota, and
Chemist of the Minnesota Agricultural Experiment Station
The Chemistry of Plant and Animal Life
_Illustrated. Cloth. 12mo. 406 pages. $1.25 net; by mail, $1.35_
"The language is, as it should be, plain and simple, free from all
needless technicality, and the story thus told is of absorbing interest
to every one, man or woman, boy or girl, who takes an intelligent
interest in farm life."--_The New England Farmer._
"Although the book is highly technical, it is put in popular form and
made comprehensible from the standpoint of the farmer; it deals largely
with those questions which arise in his experience, and will prove an
invaluable aid in countless directions."--_The Farmer's Voice._
Dairy Chemistry
_Illustrated, 190 pages, $1.00 net; by mail, $1.10_
"The book is a valuable one which any dairy farmer, or, indeed, any one
handling stock, may read with profit."--_Rural New Yorker._
Soils and Fertilizers
_Third Edition. Illustrated. $1.25 net; by mail, $1.38_
A book which presents in a concise form the principles of soil fertility
and discusses all of the topics relating to soils as outlined by the
Committee on Methods of Teaching Agriculture. It contains 350 pages,
with illustrations, and treats of a great variety of subjects, such as
Physical Properties of Soils; Geological Formation, etc.; Nitrogen of
the Soil and Air; Farm Manures; Commercial Fertilizers, several
chapters; Rotation of Crops; Preparation of Soil for Crops, etc.
THE MACMILLAN COMPANY
64-66 FIFTH AVENUE, NEW YORK
BOOKS ON AGRICULTURE
ON SELECTION OF LAND, Etc.
Thomas F. Hunt's How to Choose a Farm $1 75 net
E. W. Hilgard's Soils: Their Formation
and Relations to Climate and Plant Growth 4 00 net
Isaac P. Roberts's The Farmstead 1 50 net
ON TILLAGE, Etc.
F. H. King's The Soil 1 50 net
Isaac P. Roberts's The Fertility of the Land 1 50 net
Elwood Mead's Irrigation Institutions 1 25 net
F. H. King's Irrigation and Drainage 1 50 net
William E. Smythe's The Conquest of Arid America 1 50 net
Edward B. Voorhees's Fertilizers 1 25 net
Edward B. Voorhees's Forage Crops 1 50 net
H. Snyder's Chemistry of Plant and Animal Life 1 25 net
H. Snyder's Soil and Fertilizers. Third edition 1 25 net
L. H. Bailey's Principles of Agriculture 1 25 net
W. C. Welborn's Elements of Agriculture,
Southern and Western 75 net
J. F. Duggar's Agriculture for Southern Schools 75 net
G. F. Warren's Elements of Agriculture 1 10 net
T. L. Lyon and E. O. Fippin's The Principles of
Soil Management 1 75 net
Hilgard & Osterhout's Agriculture for Schools
on the Pacific Slope 1 00 net
J. A. Widtsoe's Dry Farming 1 50 net
ON GARDEN-MAKING
L. H. Bailey's Manual of Gardening 2 00 net
L. H. Bailey's Vegetable-Gardening 1 50 net
L. H. Bailey's Horticulturist's Rule Book 75 net
L. H. Bailey's Forcing Book 1 25 net
A. French's How to Grow Vegetables 1 75 net
ON FRUIT-GROWING, Etc.
L. H. Bailey's Nursery Book 1 50 net
L. H. Bailey's Fruit-Growing 1 50 net
L. H. Bailey's The Pruning Book 1 50 net
F. W. Card's Bush Fruits 1 50 net
J. T. Bealby's Fruit Ranching in British Columbia 1 50 net
ON THE CARE OF LIVE STOCK
D. E. Lyon's How to Keep Bees for Profit 1 50 net
Nelson S. Mayo's The Diseases of Animals 1 50 net
W. H. Jordan's The Feeding of Animals 1 50 net
I. P. Roberts's The Horse 1 25 net
George C. Watson's Farm Poultry 1 25 net
C. S. Valentine's How to Keep Hens for Profit 1 50 net
O. Kellner's The Scientific Feeding of
Animals (trans.) 1 90 net
M. H. Reynolds's Veterinary Studies for
Agricultural Students 1 75 net
ON DAIRY WORK
Henry H. Wing's Milk and its Products $1 50 net
C. M. Aikman's Milk 1 25 net
Harry Snyder's Dairy Chemistry 1 00 net
W. D. Frost's Laboratory Guide in Elementary
Bacteriology 1 60 net
I. P. Sheldon's The Farm and the Dairy 1 00 net
Chr. Barthel's Methods Used in the Examination
of Milk and Dairy Products 1 90 net
ON PLANT DISEASES, Etc.
George Massee's Diseases of Cultivated Plants
and Trees 2 25 net
J. G. Lipman's Bacteria in Relation
to Country Life 1 50 net
E. C. Lodeman's The Spraying of Plants 1 25 net
H. M. Ward's Disease in Plants (English) 1 60 net
A. S. Packard's A Text-book on Entomology 4 50 net
ON PRODUCTION OF NEW PLANTS
L. H. Bailey's Plant-Breeding 1 25 net
L. H. Bailey's The Survival of the Unlike 2 00 net
L. H. Bailey's The Evolution of Our Native Fruits 2 00 net
W. S. Harwood's New Creations in Plant Life 1 75 net
ON ECONOMICS AND ORGANIZATION
J. B. Green's Law for the American Farmer 1 50 net
J. McLennan's Manual of Practical Farming 1 50 net
L. H. Bailey's The State and the Farmer 1 25 net
Henry C. Taylor's Agricultural Economics 1 25 net
I. P. Roberts's The Farmer's Business Handbook 1 25 net
George T. Fairchild's Rural Wealth and Welfare 1 25 net
S. E. Sparling's Business Organization 1 25 net
In the Citizen's Library. Includes a chapter
on Farming
Kate V. St. Maur's A Self-supporting Home 1 75 net
Kate V. St. Maur's The Earth's Bounty. 1 75 net
G. F. Warren and K. C. Livermore's Exercises
in Farm Management 80 net
H. N. Ogden's Rural Hygiene 1 50 net
ON EVERYTHING AGRICULTURAL
L. H. Bailey's Cyclopedia of American Agriculture:
Vol. I. Farms, Climates, and Soils.
Vol. II. Farm Crops.
Vol. III. Farm Animals.
Vol. IV. The Farm and the Community.
Complete in four royal 8vo volumes, with over 2000 illustrations.
Price of sets: cloth, $20 net; half morocco, $32 net.
_For further information as to any of the above, address the
publishers._
THE MACMILLAN COMPANY
Publishers 64-66 Fifth Avenue New York
Cyclopedia of American Agriculture
EDITED BY L. H. BAILEY
Of Cornell University, Editor of "Cyclopedia of American
Horticulture," Author of "Plant Breeding," "Principles of
Agriculture," etc.
WITH 100 FULL-PAGE PLATES AND MORE THAN 2000 ILLUSTRATIONS IN THE
TEXT--FOUR VOLUMES--THE SET: CLOTH, $20 NET--HALF MOROCCO, $32
NET--CARRIAGE EXTRA
Volume I--FARMS
The Agricultural Regions--The Projecting of a Farm--The Soil
Environment--The Atmosphere Environment.
Volume II--CROPS
The Plant and Its Relations--The Manufacture of Crop Products--North
American Field Crops.
Volume III--ANIMALS
The Animal and Its Relations--The Manufacture of Animal Products--North
American Farm Animals.
Volume IV--THE FARM AND THE COMMUNITY
Economics--Social Questions--Organizations--History--Literature, etc.
"Indispensable to public and reference libraries ... readily
comprehensible to any person of average education."--_The Nation._
"The completest existing thesaurus of up-to-date facts and opinions on
modern agricultural methods. It is safe to say that many years must pass
before it can be surpassed in comprehensiveness, accuracy, practical
value, and mechanical excellence. It ought to be in every library in the
country."--_Record Herald_, Chicago.
PUBLISHED BY
THE MACMILLAN COMPANY
64 66 FIFTH AVENUE, NEW YORK
*** End of this LibraryBlog Digital Book "Human Foods and Their Nutritive Value" ***
Copyright 2023 LibraryBlog. All rights reserved.