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Title: Detection of the Common Food Adulterants
Author: Bruce, Edwin M.
Language: English
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Detection of the Common
Food Adulterants
BY
EDWIN M. BRUCE
INSTRUCTOR IN CHEMISTRY, INDIANA STATE NORMAL SCHOOL
LONDON
ARCHIBALD CONSTABLE & CO., LTD.
10 ORANGE STREET, LEICESTER SQUARE, W.C.
1907
_Copyright, 1907_
BY D. VAN NOSTRAND CO.
PREFACE
Because of the recent agitation of the pure food question throughout the
country, health officers, food-inspectors, and chemistry teachers and
students are constantly called upon to test the purity of various foods.
And this usually involves nothing more than making simple qualitative
tests for adulterants. In view of the fact that there is now no text or
manual devoted exclusively to the qualitative examination of foods, this
little book is offered to those who are interested in this work.
Its aim is to bring together in one small book the best and simplest
qualitative tests for all the common food adulterants. It contains a
brief statement of the adulterants likely to be found and the reason for
their use. It is hoped that it will be specially valuable to chemistry
teachers in furnishing excellent supplementary work in qualitative
analysis. But it is hoped that it will find its greatest usefulness in
contributing something toward the great pure food reform.
It is impossible to make due mention of all the sources from which these
various tests have been collected, but where possible, the author’s name
has been associated with the test.
TERRE HAUTE, IND.
_March 25, 1907._
TABLE OF CONTENTS
CHAPTER I PAGE
DAIRY PRODUCTS 1
=Milk=--Adulterations of--Coloring matters--Annatto--Caramel--
Coal-tar colors--Preservatives--Formaldehyde--Boric acid--Salicylic
acid--Gelatin--Starch.
=Butter=--Adulterations of--Coloring matter--Preparation of sample
--Annatto--Coal-tar colors--Saffron--Turmeric--Marigold--Process or
renovated butter--Oleomargarine--Cottonseed oil.
CHAPTER II
MEATS AND EGGS 8
Adulterations of--Fresh and smoked--Preservatives--Potassium
nitrate--Boric acid--Sulfurous acid--Salicylic acid--Benzoic acid--
Canned--Preservatives (same as those of fresh and smoked meat)--
Heavy metals--Coloring matter (see under sausages, etc.)--Fish,
salt, dried and oysters--Preservatives--Boric acid (same under
smoked and fresh meat)--Coloring matter--Aniline red and cochineal-
carmine--In sausages, chopped meat, preparations and corned meat--
Starch--In sausages, deviled meat and similar products--Diseased
meats--Horse-flesh in sausages and in mince-meat.
=Eggs=--Test for age.
CHAPTER III
CEREAL PRODUCTS 16
=Flour=--Adulteration of--Alum--Copper sulfate--Substituted flours
--General test--Corn meal in wheat flour--Wheat flour in rye flour
--Ergot in rye flour.
=Bread=--Adulterations of--Alum--Copper sulfate.
=Ginger Cake=--Adulterations of--Stannous chlorid.
CHAPTER IV
LEAVENING MATERIALS 20
=Baking Powders=--Adulterations of--Tartaric acid (free or
combined)--Tartaric acid (free)--Sulfates (calcium, etc.)--Gypsum--
Ammonium salts--Alum.
=Cream of Tartar=--Adulterations of--Tartaric acid (free or
combined)--Aluminium salts--Ammonia--Earthy materials.
CHAPTER V
CANNED AND BOTTLED VEGETABLES 24
Adulterations of--Preservatives--Preparation of sample--
Formaldehyde--Sulfurous acid and the sulfites--Salicylic acid--
Saccharin--Benzoic acid--Coloring matter--Cochineal--Coal-tar dyes
--Copper salts--In green pickles, beans, peas, etc.--Turmeric--In
mixed pickles--Heavy metals (other than copper, same as under
meats)--Soaked vegetables--Peas, beans and corn--Alum--In pickles--
Examination of the can or box.
CHAPTER VI
FRUITS AND FRUIT PRODUCTS 33
Adulterations of--Preservatives--Preparation of sample--Salicylic
acid--Benzoic acid--Saccharin--Coloring matter--Coal-tar dyes--
Cochineal--Acid magenta--Apple juice in jellies made from small
fruits--Detection (see test for starch)--Starch--In jellies, jams
and such products--Gelatin--In jellies--Agar agar--Heavy metals--
Arsenic.
CHAPTER VII
FLAVORING EXTRACTS 42
=Lemon Extract=--Lemon oil--Citral--Oil of citronella--Tartaric or
citric acid--Methyl alcohol--Coloring matter--Turmeric--Coal-tar
colors.
=Vanilla Extract=--Adulterations of--Preliminary test--Alkali--
Foreign resins--Caramel--Tannin--Coumarin.
CHAPTER VIII
SACCHARINE PRODUCTS 49
=Honey=--Adulterations of--General observations--Cane sugar--
Commercial glucose syrup--Gelatin.
=Maple Syrup=--Adulterations of--General examination--Glucose.
CHAPTER IX
SPICES 51
=Mustard=--Adulterations of--Flour--Coloring matter--Turmeric--
Martius yellow or analogous coal-tar coloring matter--Cayenne
pepper.
=Pepper=--Adulterations of--General test--Ground olive stones--
Cayenne pepper.
CHAPTER X
VINEGAR 55
Adulterations of--Preparation of sample--General observations--
Free mineral acids--General tests--Sulfuric acid--Hydrochloric acid
(free)--Malic acid--Coloring matter--Caramel--Coal-tar colors--In
wine vinegar--Free tartaric acid--In wine vinegar.
CHAPTER XI
FATS AND OILS 60
=Lard=--Adulterations of--Cottonseed oil--Cottonseed stearin--Beef
stearin.
=Olive Oil=--Adulterations of--General test--Cottonseed oil--Peanut
oil--Sesame oil--Rape oil.
CHAPTER XII
BEVERAGES 65
=Coffee=--Adulterations of--General test--Coloring matter--
Imitation coffee beans--Chicory.
=Tea=--Adulterations of--Foreign leaves--Exhausted tea leaves--Lie
tea--Facing--Catechu.
PURE FOOD TESTS
CHAPTER I
DAIRY PRODUCTS
MILK
Milk is adulterated by watering, removing the cream or by adding some
foreign substance. Formaldehyde, boric acid or salicylic acid may be
added to preserve the milk. Annatto, caramel or some coal-tar dye is
added, sometimes to improve the color of the milk, and at other times to
cover up traces of watering. Gelatin and starch are added for the same
purpose, though they are not frequently used.
ARTIFICIAL COLORING MATTER
ANNATTO
Add acid sodium carbonate to a sample of the milk until it shows a
slight alkaline reaction. Immerse a piece of filter-paper and leave it
in for 12 or 15 hours. If annatto is present, there will be a
reddish-yellow stain on the paper.
CARAMEL
_Leach’s Method._--Warm 150 cc. of the sample and add 5 cc. of acetic
acid, then continue heating it nearly to the boiling point, stirring
while it is being heated. Separate the curd by gathering it with the
stirring rod or by pouring through a sieve. Press out all the whey from
the curd and macerate the latter for several hours (10 to 12 hours) in
50 cc. of ether. It is best to do this in a tightly corked flask,
shaking it frequently. If the milk was uncolored or colored with annatto
the curd when thus treated will be white. If the curd is a dull brown
color caramel was probably used to color the milk. Confirm its presence
by shaking a portion of the curd with concentrated hydrochloric acid
(sp. gr. 1.20) and gently heating. If the acid solution turns blue while
the curd does not change its color, caramel was used to color the milk.
(Remember that the ether-extracted curd must be brown.)
COAL TAR COLORS
_Lythgoe’s Method._--Mix in a porcelain vessel about 15 cc. each of the
sample of milk and hydrochloric acid (sp. gr. 1.20) and break up the
curd into coarse lumps by shaking gently. If an azo-color was used to
color the milk this curd will be pink, but the curd of normal milk will
be white or yellowish.
STARCH
The presence of starch in milk may be detected by heating a small
quantity of the milk to boiling. When it has cooled add a drop of iodin
in potassium iodid, and if starch is present there will be a blue
coloration.
GELATIN
_A. W. Stokes’ Method._--Dissolve 1 part by weight of mercury in 2 parts
of nitric acid (sp. gr. 1.42). Add 24 times this volume of water. Mix
equal volumes (about 10 cc.) of this reagent and the milk or cream,
shake well and add 20 cc. of water. Shake again and, after standing 5
minutes, filter. When a great quantity of gelatin is present the
filtrate will be opalescent instead of perfectly clear. To a little of
this filtrate in a test tube add the same volume of a saturated aqueous
solution of picric acid. If much gelatin is present a yellow precipitate
is produced, smaller amounts produce a cloudiness. If the filtrate is
perfectly clear gelatin is absent and picric acid may be added without
producing any noticeable effect.
PRESERVATIVES
FORMALDEHYDE
_Hehner’s Sulfuric Acid Test._--Put 10 cc. of the suspected milk in a
wide test tube and pour carefully down the side of the inclined tube
about 5 cc. commercial sulfuric acid so that it forms a separate layer
at the bottom. A violet coloration at the union of the two liquids
indicates the presence of formaldehyde. If the commercial acid is not
available, the pure acid may be used, but a few drops of ferric chloride
must be added. Sometimes the charring effect of the acid makes it
advisable to use the following test:
_Hydrochloric Acid Test._--2 cc. of 10 per cent ferric chloride is added
to one liter of commercial hydrochloric acid sp. gr. 1.2 (or any
quantity in this proportion). To 10 cc. of this mixture add 10 cc. of
the milk to be tested. Heat the mixture slowly nearly to the boiling
point, in an evaporating dish, but agitating it all the while to prevent
the curd collecting in one mass. If formaldehyde is present, there will
be a violet coloration. It is said that by this test as small a
quantity of formaldehyde as 1 part in 250,000 parts of milk can be
detected. It is not so sensitive in sour milk.
BORIC ACID
_Turmeric Paper Test._--Incinerate some of the milk, and acidulate the
ash with a very few drops of dilute hydrochloric acid and afterwards
dissolve it in a few drops of water. Place a strip of turmeric paper in
this solution for a few minutes, then remove and dry it. If boric acid
either free or combined is present, the turmeric paper will be turned to
a cherry-red color.
_Another way of making this test._--U. S. Dep. of Agr., Div. of Chem.,
Bul. 65, p. 110: Make strongly alkaline with lime water, 25 grams of the
milk, and evaporate to dryness on the water bath. Destroy the organic
matter by igniting the residue. Dilute with 15 cc. of water and acidify
with hydrochloric acid. Then add 1 cc. of the concentrated acid. Dip a
piece of delicate turmeric paper in the solution; and if borax or boric
acid is present, it will have a characteristic red color when dry.
Ammonia changes it to a dark blue green, but the acid will restore the
color.
(Turmeric paper may be prepared by dipping pieces of smooth, thin filter
paper in a solution of powdered turmeric in alcohol.)
SALICYLIC ACID
(This is not often used as a preservative of milk.)
_Leach suggests the following method for its detection._--Dissolve one
gram of mercury in 2 grams of nitric acid (sp. gr. 1.42) and then add to
the solution the same volume of water. Add 1 cc. of this reagent to 50
cc. of the milk to be tested, and shake and filter. The perfectly clear
filtrate is shaken with ether and the ether extract evaporated to
dryness. Then add a drop of ferric chlorid solution, and a violet color
will be produced if salicylic acid is present.
BUTTER
Butter is often colored with annatto, saffron, turmeric, marigold or
coal-tar colors. By a certain process, stale or old butter is sometimes
worked over and made to appear fresh for a time. This is sold under the
name of “process” or “renovated” butter. Foreign fats like cottonseed
oil, sesame oil, or oleomargarine may be substituted for or added to
pure butter.
COLORING MATTER
_Martin’s Test._--Add 2 parts of carbon bisulfid, a little at a time and
with frequent shaking, to 15 parts of alcohol. Shake 25 cc. of this
solution with 5 grams of the butter, and let stand for some time. The
carbon bisulfid dissolves out the fatty matter and settles to the
bottom. The alcohol remains on top and will dissolve out any artificial
colors that may be present. If only a little coloring matter is present
use more of the butter.
ANNATTO
Evaporate a portion of the extract to dryness and add sulfuric acid to
the residue. If annatto is present a greenish-blue color forms. Should a
pink tint result the presence of a coal-tar color is to be suspected.
COAL-TAR COLORS
These colors will dye wool or silk if pieces of the fiber are boiled in
the diluted alcoholic extract, which has first been acidified with
hydrochloric acid. The normal butter coloring matter will not dissolve
when thus treated.
_Geisler’s Method._--To a few drops of the clarified fat on a porcelain
surface, add a very little fullers’ earth. If a pink to violet-red
coloration is produced in a short time the presence of an azo-color is
indicated.
SAFFRON
When saffron is present, nitric acid colors the alcoholic extract green,
and hydrochloric acid colors it red.
TURMERIC
Add ammonia to the alcoholic extract, and if it turns brown it indicates
the presence of turmeric.
MARIGOLD
Add silver nitrate to the extract, and if it turns black the presence of
marigold is indicated.
PROCESS OR RENOVATED BUTTER
Heat a little of the suspected butter in a spoon or dish, and if it is
process butter it will sputter, but not foam much. Make the test also
with some butter known to be pure and fresh.
_Hess and Doolittle Test._--Melt some of the butter (say 40 grams) at
about 50° C. If the butter is pure and fresh the melted fat will clear
up almost as soon as it is melted, while the fat of process butter
remains turbid for quite a while. After most of the curd has settled,
decant as much as possible of the fat. Pour the remainder on a wet
filter. Add a few drops of acetic acid to the water that runs through
from the filter, and boil. If it was ordinary butter this filtrate will
become milky, but if process butter a flocculent precipitate will form.
OLEOMARGARINE
Immerse a test tube, containing some of the filtered fat, in boiling
water for 2 minutes. Make a mixture of 1 part glacial acetic acid, 6
parts ether, and 4 parts alcohol. Add to 20 cc. of this mixture in a 50
cc. test tube, 1 cc. of the heated fat which may be transferred by means
of a hot pipette. Stopper the tube and shake it well. Immerse in water
at 15° or 16° C. Pure butter when thus treated remains clear for quite a
while. There will be only a very little deposit after standing an hour,
but oleomargarine gives a deposit almost immediately, and in a few
minutes there will be a copious precipitate.
When the oleomargarine in butter is in about the proportion of 1 : 10,
it will not separate much short of 15 minutes.
COTTONSEED OIL
The presence of this oil may be detected by Halpen’s test, which is
given under lard, page 60.
CHAPTER II
MEATS AND EGGS
Meats are preserved by treating them with potassium nitrate, boric acid,
sulfurous acid, salicylic acid, or benzoic acid. Cheap meat may be
substituted for the more expensive. A few cases of horse meat in mince
meat and sausages have been discovered. Diseased and stale meats have
been found on the market. Canned meats often contain zinc, tin, and
lead, and sometimes even arsenic. Aniline-red or cochineal-carmine may
be added to improve the color of chopped or ground meats. Starch is
sometimes added to sausage and similar meat. Fish and oysters may be
preserved with boric acid or borax.
FRESH AND SMOKED PRODUCTS--PRESERVATIVES
POTASSIUM NITRATE (SALTPETER)
Corned and smoked meats are usually preserved with saltpeter. Since
smoked and cured meats are used in making potted meats, saltpeter is
quite frequently found in the latter. It may be detected by the usual
test for nitrates since no other nitrate is apt to be present, though
one may identify the metal by the qualitative test for potassium.
To test for nitrates treat a little of the meat with 2 or 3 cc. of a 1
per cent solution of diphenylamine in strong sulfuric acid. If a
nitrate is present a deep blue color forms instantly, which is not
obscured by the charring effect of the acid.
BORIC ACID
Pick apart into fine pieces about 25 or 50 grams of the lean meat and
warm with a little water which has a few drops of hydrochloric acid in
it. Soak a piece of turmeric paper in the extract, and if boric acid is
present the paper will be colored rose-red when it is dry. A weak alkali
turns this colored paper olive.
Another method is to burn a piece of the meat to an ash, after being
treated with lime water. Make a solution of the ash and make slightly
acid with hydrochloric acid. Then test with the turmeric paper with the
same results as in the above method.
SULFUROUS ACID
U. S. Dep. Agr., Bureau Chem., Bul. 13, Part 10: Digest 40 or 50 grams
of the meat in hot water, treat with 10 cc. glacial phosphoric acid to
coagulate the proteids. Strain through a cotton bag and transfer the
filtrate to a short-necked flask and distil receiving the first part of
the distillate in a solution of iodin. Boil, and add barium chloride. If
sulfurous acid is present, it will be oxidized to sulfuric acid and
precipitated as barium sulfate by the barium chlorid. More than a mere
trace of the precipitate proves that some sulfite was used to preserve
the meat.
Another method suggested by Kämmerer is to place the meat on paper,
which has been saturated with potassium iodate moistened with dilute
sulfuric acid (1 : 8); nitric oxid must not be present. If sulfurous
acid is present a deep blue color forms at once. A trace of this color
may form after some time with meat that is not fresh, hence this method
cannot be used in examining canned meat.
SALICYLIC ACID
Heat 50 grams of the meat in 50 cc. of water. Add 10 cc. of a strong
solution of glacial phosphoric acid and strain through a cotton bag.
Extract the filtrate with a little ether (about 50 cc.) in a separatory
funnel. Let the ether evaporate spontaneously. Take up the residue with
3 cc. of water, and add one or two drops of a one-half per cent solution
of ferric chlorid. If salicylic acid is present the mixture will be
purple or violet.
Leach makes the same test by slightly acidifying a portion of the lean
meat, then extracting with ether, and evaporating to dryness and testing
the residue with a drop of ferric chlorid solution. A deep violet
coloration is produced if salicylic acid is present.
BENZOIC ACID
_Mohler’s Method._--Prepare a sample as in the test for salicylic acid
by heating 50 grams of the meat in 50 cc. of water. Add 10 cc. of a
concentrated solution of glacial phosphoric acid, and strain through a
cotton bag. Neutralize with sodium hydrate and evaporate to dryness or
to a small volume. After treating with 3 cc. of concentrated sulfuric
acid, heat till white fumes appear. Add 4 or 5 crystals of potassium
nitrate and continue heating until the solution is colorless or nearly
so. When cool dilute with water, add an excess of ammonia, and place in
a narrow vessel like a test tube. Add one or two drops of ammonium
sulfid carefully so that the liquids do not mix. If the surface of the
liquid immediately becomes red, benzoic acid is present.
If this test is not carefully performed, it is worthless, as other
substances give similar results.
Confirm its presence by neutralizing the aqueous solution of the
extracted benzoic acid with sodium hydroxid; concentrate to a very small
volume. Acidify with sulfuric acid. A white flocculent precipitate shows
the presence of considerable benzoic acid.
CANNED MEAT
If in preparing canned meat only fresh meat is used, there is little
need for the use of preservatives, but as considerable smoked and cured
meat is thus used, preservatives may find their way into canned meat.
The same preservatives should be looked for as in fresh and smoked meat
and the same test made for each.
HEAVY METALS
_A. H. Allen’s Method._--About 25 grams of the substance is mixed slowly
with enough strong, pure sulfuric acid to just moisten the mass,
avoiding an excess. Heat on a water-bath for a short time, then raise
the temperature gradually, and maintain till the chlorids seem to be
decomposed. It must not be hot enough, however, to volatilize the
sulfuric acid. Then add 1 cc. of strong nitric acid and heat till red
fumes are given off. Freshly ignited magnesia in the proportion of 0.5
gram for each cc. of sulfuric and nitric acid previously used is now
stirred into the mass and the whole ignited at a dull red heat. This is
best done in a gas-muffle. When cool, moisten the ash with nitric acid
and gently re-ignite, repeating this treatment till the carbon is
entirely consumed. Treat the residue with 8 or 10 drops of strong
sulfuric acid, heat till fumes are given off, cool, boil with water,
dilute to about 100 cc. and saturate with hydrogen sulfid, filter,
examine as follows:
==========================++===========================================
Zinc and iron may be in ||Lead, tin, copper, and calcium, if present,
solution. Add bromine ||will be in the precipitate and residue.
water to destroy hydrogen ||Fuse the mass in a porcelain crucible for
sulfid and to oxidize the ||at least ten minutes with 2 grams each of
iron, boil and add ammo- ||potassium and sodium carbonates and half
nium hydrate in excess, ||as much sulfur. After cooling, boil with
boil again and filter. ||water and filter.
---------------+----------++---------------------------+---------------
The precipitate|Filtrate, ||Residue. Add hydrochloric |The filtrate may
will contain |when blue,||acid and boil as long as |contain tin.
the iron and |proves the||hydrogen sulfid is given |Acidify with
the phosphates.|presence ||off. A few drops of bro- |acetic acid, and
|of nickel.||mine water will complete |if tin is pres-
| ||the oxidation of the |ent a yellow
| ||copper sulfid. Filter, and|precipitate of
| ||add ammonium hydroxid in |stannic sulfid
| ||excess to the filtrate. |will form.
| ||When the filtrate is blue,|
| ||it indicates the presence |
| ||of copper. Acidify the |
| ||filtrate with acetic acid |
| ||and test for lead by |
| ||adding potassium chromate,|
| ||a yellow precipitate being|
| ||formed when it is present.|
---------------+----------++--------------------------+----------------
|I. Heat to|| |
|boiling || |
|and add || |
|potassium || |
|ferrocya- || |
|nid. A || |
|white pre-|| |
|cipitate || |
|or turbi- || |
|dity in- || |
|dicates || |
|_zinc_. || |
===============+==========++==========================+================
FISH SALT DRIED AND OYSTERS
This kind of meat is often preserved with boric acid and borax. They may
be detected by the method given under fresh and smoked meat.
COLORING MATTER
Sausages and other chopped meat preparations, together with corned meat
that has been cured without saltpeter, are often treated with artificial
coloring matter.
Aniline red and cochineal carmine are usually employed for this purpose.
The former may be detected, according to Allen, by picking the meat
apart and treating it with methylated spirit, strain or filter the
extract and take up with water. Then a piece of white wool (nun’s
veiling will do) is immersed in the boiling liquid and, if it is dyed
red, rosaniline is present.
Cochineal-carmine may be detected by the method used by Klinger and
Bujard. Cut up fine about 20 grams of the meat and heat in a water-bath
with water and glycerine mixed in equal parts. If the above coloring
matter is present the liquid will become quite red in color, if not
present a slight yellow color results from this treatment. If a
spectroscope is available this dye is easily recognized.
STARCH
IN SAUSAGE, DEVILED MEAT, AND SIMILAR PRODUCTS
Cracker and bread crumbs are often added to these preparations and their
presence is best detected by examining the amount of starch present. Do
this by boiling some of the sample in water, and when cool adding a drop
or two of iodin reagent. The usual blue color is produced if much
starch is present. If there is only a little starch, it may be necessary
to examine it under the microscope to determine whether the starch is
from the pepper and other spices used or from some cereal.
DISEASED MEAT
_The following method is recommended by Ebers._--Hold a small piece of
the suspected meat over a mixture of 1 cc. hydrochloric acid, 3 cc.
alcohol, and 1 cc. of ether. The formation of ammonium chlorid fumes
shows that decomposition has begun. Do not mistake the fumes of the acid
for those of ammonium chlorid.
HORSE FLESH
IN SAUSAGE AND MINCE MEAT
This sophistication is not common in this country. Horse flesh is
detected by testing for glycogen, which is present in it in larger
quantities than in other meats.
_Courley & Coremon’s Test._--Boil 50 grams of the meat for a half hour
with water, strain, and to a portion of the filtrate add a few drops of
potassium iodid-iodin solution (potassium iodid 0.4 gram; iodin 0.1
gram; water 20 cc.). If considerable horse meat is present the glycogen
will color the liquid dark brown, which disappears on heating, but
returns on cooling.
EGGS
It sometimes happens that one wishes to know the age of eggs without
opening them.
_Delarne’s Test._--Place the egg in a 10 per cent solution of common
salt. Perfectly fresh eggs sink to the bottom. Those remaining
immersed, but suspended in the liquid, are at least three days old,
while those rising to the surface and floating are more than five days
old. The older the egg, the higher it floats and the more it will stand
on end. This test is not applicable to eggs that have been preserved.
Hold the egg between a bright light and the eye, and if the air chamber
is small, and no dark spots but instead a rather uniform rose-colored
tint is seen, the egg is fresh. If the contents appear cloudy and the
air chamber larger, the egg is not fresh. The darker the contents of the
egg the older it is.
CHAPTER III
CEREAL PRODUCTS
FLOUR
Sometimes a cheaper or inferior grade of flour is substituted for one of
higher quality, and even a different kind of flour may be substituted,
as corn meal in wheat flour, or wheat in rye flour. Alum may be added by
millers to cover up traces of bad flour, and by bakers to make the bread
white when a bad or cheap flour is being used. Copper sulfate also may
be added to improve the appearance. Occasionally rye flour is made from
rye upon which ergot has developed. Stannous chlorid and potassium
carbonate are added to ginger cake to give the same color to the product
made of molasses and a poor grade of flour as that made from good flour
and honey.
ALUM
_Wynther Blyth Method._--Add a little water to the sample and macerate.
Soak pieces of gelatin in the solution and leave for a half day, remove
the gelatin and dip the pieces in a mixture of equal volumes of a fresh
tincture of logwood and a saturated solution of ammonium carbonate. The
gelatin strips will turn blue if alum is present.
_Bell & Carter Method._--Make a fresh 5 per cent tincture of logwood in
methyl alcohol. Dampen about 10 grams of the flour with water and add 1
cc. of the logwood tincture and the same quantity of a saturated
solution of ammonium carbonate. Pure flour gives a pinkish color which
fades to buff or brown. The presence of alum produces a lavender or
bluish tint which becomes more distinct as it dries.
COPPER SULFATE
This adulterant may be detected in either flour or bread, by soaking the
flour or bread in a dilute solution of potassium ferrocyanid acidulated
with acetic acid. If copper be present a purplish or reddish-brown
coloration will be produced.
SUBSTITUTED FLOURS
_Vogel’s Method._--Make a mixture of alcohol (70 per cent), 95 parts,
hydrochloric acid 5 parts. Treat a sample of the flour in a test tube
with this reagent. Shake well. Heat to boiling and allow to settle. A
colorless fluid shows the flour to be pure, a straw-colored tint
indicates the presence of gruffs with bran, an orange-yellow proves the
presence of corn-cockle flour, a flesh-colored liquid indicates the
presence of ergot, while a green color indicates buckwheat flour.
CORN MEAL IN WHEAT FLOUR
_Kraemer claims to be able to detect as small amount as 5 per cent of
maize in wheat flour, by the following test._--Mix a gram of the flour
with 15 cc. of good glycerin, and heat to boiling for a short time. If
corn meal is present, there will be an odor like that of pop corn.
WHEAT IN RYE FLOUR
_Kleeburg recommends the following test._--A little of the flour is
mixed on a piece of common window glass or microscope slide, with
sufficient water (at 45° C.) to float the flour particles. Spread the
mixture out over the glass, and press another glass down upon it. When
wheat flour is present, white spots will be seen, and if the glasses are
slid upon each other the spots will pull out into threads, and the
thicker and longer they are the more wheat flour there is present.
ERGOT IN RYE FLOUR
_Boettger gives the following chemical test for ergot._--Heat 10 to 15
minutes with an equal quantity of ether, adding a few crystals of oxalic
acid. When ergot is present a reddish color develops.
_Another Method._--Bul. 51, Bureau of Chem.
Digest 20 grams of the suspected flour, with boiling alcohol, till no
more color is extracted. Add 1 cc. of sulfuric acid (1 : 3), and if
ergot is present the solution will be colored red.
BREAD
ALUM
Moisten a piece of the bread with water, and then with a logwood
solution (5 grams logwood digested in 100 cc. of alcohol). If alum is
present the bread will become lavender blue in two or three hours. Pure
bread would have a red-brown tint. To prove the presence of alum, the
blue color must be permanent at the temperature of boiling water. (The
logwood used in this test must be pure.)
_Blyth’s Test._--Macerate 150 grams of the sample for 45 or 50 hours in
a couple liters of water; after straining through muslin, evaporate to a
small volume over a low flame. Immerse a strip of gelatin in this
liquid, and then in a logwood solution (same as in last test), and if
alum is present it will acquire the lavender color.
If the bread in either of these tests is sour, the following
modification (Vanderplanken) must be made. Reduce 15 grams of the sample
to a paste with water and some pure chlorid of sodium, adding 10 drops
of a fresh alcoholic solution of logwood, after which add 5 grams of
pure potassium carbonate. Mix well, and after washing with 100 cc. of
water into a vessel allow to settle. If alum is present the liquid will
soon become reddish-violet, and if not present it will be blue.
COPPER SULFATE
SEE TEST FOR COPPER SULFATE IN FLOUR
GINGER CAKE
Tin may be detected by the method for heavy metals under meat.
CHAPTER IV
LEAVENING MATERIALS
BAKING POWDERS
Baking powders consist of bicarbonate of soda and an acidifying agent as
acid potassium tartrate, acid calcium phosphate, tartaric acid or alum.
Some powders contain both acid calcium phosphate and alum. The kind of
powder is determined by testing for these. Gypsum has been added to
baking powders to increase the weight.
TARTARIC ACID
FREE OR COMBINED
_Wolff’s Method._--If no starch is present, mix a little of the powder
with some dry resorcin. Add a few drops of sulfuric acid and heat
gently. A rose-red color forms if tartaric acid or tartrates are
present. The color should disappear when diluted with water. When starch
is present, mix well by shaking about 5 grams of the powder with 250 cc.
of cold water. Let the insoluble matter settle and pour the liquid upon
a filter. Evaporate the filtrate to dryness, treat the powdered residue
with a few drops of a 1 per cent solution of resorcin. Add 3 cc. of
strong sulfuric acid, heat slowly. A rose-red color forms if tartaric
acid is present. The color should be destroyed on the addition of
water. This test is applicable in the presence of phosphates and the
acid may be free or combined.
TARTARIC ACID
FREE
Make an absolute alcoholic extract of 5 grams of the powder and
evaporate the alcohol. Add sufficient dilute ammonia to dissolve the
residue, place in a test tube and drop in a crystal or two of silver
nitrate. Heat gently, and a silver mirror will form if tartaric acid is
present.
SULFATES
CALCIUM, ETC.
Boil a portion of the sample gently with strong hydrochloric acid, add
barium chlorid. A white precipitate of barium sulfate will form if
sulfuric acid is present.
GYPSUM
CALCIUM SULFATE
Ash a portion of the sample and make the usual qualitative tests for
calcium sulfate.
AMMONIUM SALTS
Extract a few grams of the sample with cold water, boil the extract with
sodium hydroxid and place a piece of moist red litmus paper in the
steam. It will be colored blue if ammonia is present.
ALUM
Reduce to an ash about 2 grams of the powder in a platinum dish. Extract
with boiling water, add ammonium chlorid solution to the filtrate until
a distinct odor of ammonia is given off.
If a flocculent precipitate forms it indicates the presence of alum.
This test for alum is applicable in the presence of phosphates.
_Mrs. Richards._--Cover some logwood chips (they must be pure) with
water and bring to a boil. Repeat this four times, saving only the last
decoction. Shake some of the sample (a couple of teaspoonfuls) in a
beaker half full of water. When it ceases effervescing, strongly acidify
with acetic acid. Add a few drops of the logwood extract, and if alum is
present a bluish-red color will appear.
CREAM OF TARTAR
Cream of tartar is bitartrate of potassium and is obtained from the lees
deposited in wine casks. If gypsum has been used to clarify the wine, it
will be present in the cream of tartar as calcium tartrate.
Other adulterants of cream of tartar are acid calcium phosphate, starch,
gypsum, and alum.
TARTARIC ACID
FREE OR COMBINED
If the sample is known to be free from starch the following test may be
made:
Mix a bit of the powder with a small quantity of dry resorcin and add a
few drops of concentrated sulfuric acid. Heat slowly, and if a rose-red
color forms, which disappears when diluted with water, there is present
either tartaric acid or a tartrate.
When the sample contains starch, shake about 4 or 5 grams of it a number
of times with 250 cc. of cold water in a large flask. Pour on a filter
after the insoluble material has settled and evaporate the filtrate to
dryness. The residue is to be tested for tartaric acid and tartrates,
the same as when starch was absent.
ALUMINIUM SALTS
Mix equal quantities (about 1 gram) of the sample and sodium carbonate
and burn to an ash. Extract with boiling water and filter. Add to this
filtrate enough ammonium chlorid solution to cause a distinct evolution
of ammonia. The formation of a flocculent precipitate shows the presence
of aluminium. This test may be used when phosphates are present.
AMMONIA
PRESENT IN THE FORM OF AMMONIA ALUM OR AMMONIUM CARBONATE
Make a cold water extract of the powder and boil it with sodium
hydroxid. Test the steam with moist red litmus paper.
EARTHY MATERIALS
Treat the sample with warm potassium hydroxid. A residue indicates some
earthy material.
CHAPTER V
CANNED AND BOTTLED VEGETABLES
No class of foods on the market has less need for antiseptics than
canned goods, yet their use is rather common. Products thus treated are
easier canned and are not so apt to spoil. The chemicals used as
preservatives are sulfurous acid, and the sulfites, salicylic acid and
saccharin, benzoic acid, and sometimes formaldehyde. Sulfurous acid is
used to bleach such foods as canned corn. Saccharin possesses some
antiseptic properties, but its main use is as a sweetener. Alum is used
to make pickles hard and crisp.
Some canned or bottled goods, as tomato-catsup, is colored with
cochineal or coal-tar dyes. Green pickles, beans, peas, and such
vegetables are colored by copper salts or are cooked in copper vessels,
with the addition of acetic acid, hence the beautiful green color.
Turmeric is sometimes used to color mixed pickles.
The heavy metals as lead, zinc, and tin are generally present in canned
goods, the amount varying with the corrosive power of the vegetable.
When there is a year of scarcity in corn, peas, beans, and such
vegetables, the dried product is often soaked and canned. Some of this
goods is sold for the regular green vegetable, while some may be
properly marked “Soaked Goods.”
PRESERVATIVES
It is best to make a systematic examination for the different
preservatives. The sample may be prepared by mixing 50 grams of the
pulped material with sufficient water in a 250 cc. graduated flask. Add
phosphoric acid till distinctly acid in reaction. Fill to the mark with
water. Place in a distilling flask, and distil in a linseed oil or a
paraffin bath till 30 cc. have been collected. Save this distillate for
the following tests.
FORMALDEHYDE
To 5 cc. of the above distillate in a test tube, add 2 or 3 drops of a 1
per cent aqueous solution of phenol and mix well. Incline the tube and
carefully pour down the side 5 cc. of concentrated commercial sulfuric
acid so that the two liquids do not mix. If formaldehyde is present
there will be a crimson zone at the plane of union of the solutions.
This coloration takes place when the formaldehyde is present in the
proportion of 1 part in 100,000 parts. When there is a greater quantity
of formaldehyde present a white turbidity or a light-colored precipitate
forms above the coloring.
_Phenylhydrazine Hydrochloric Test._--Dissolve 2 grams of
phenylhydrazine hydrochlorid and 3 grams of sodium acetate in 20 cc. of
water. Add 2 to 4 drops of this reagent and the same number of drops of
sulfuric acid to 1 or 2 cc. of the above distillate, to be examined in a
test tube. A green coloration is produced when formaldehyde is present.
_Hydrochloric Acid Test._--Add 5 cc. of the distillate to be tested to
about 5 cc. of milk known to be pure, and about 10 cc. of concentrated
hydrochloric acid (sp. gr. 1.2) which contains 1 cc. of a 10 per cent
ferric chlorid solution to each 500 cc. of the acid. Heat slowly to 80°
or 90° C. over the free flame, agitating it at the same time to break up
the curd. A violet coloration indicates formaldehyde.
SULFUROUS ACID AND THE SULFITES
Free sulfurous acid is not largely used as a food preservative, though
its salts are quite commonly employed.
_Detection._--Mix 150 grams of the finely ground sample with enough
water to make a thin paste. Acidify with phosphoric acid and distil till
25 cc. have been collected. (The delivery tube of the condenser should
dip below the surface of a little water.) Treat the distillate with a
few drops of bromine water and boil for a short time. If a precipitate
forms on the addition of barium chlorid the presence of sulfurous acid
is indicated.
SALICYLIC ACID
Acidify 50 cc. of the sample with sulfuric acid, and shake vigorously
with 50 cc. of a mixture of equal parts of ether and petroleum spirit.
When the liquids have separated, draw off as much as possible of the
solvent and filter. If an emulsion forms use a centrifugal machine, and
evaporate with a small flame. If needle-shaped crystals form, salicylic
acid is present. Add a few drops of water and a drop of very dilute
ferric chlorid solution in such a way that the solutions will come
together slowly. The presence of salicylic acid gives a purple or violet
color.
SACCHARIN
This is used quite extensively as a sweetening agent in canned sweet
corn, and other similar products.
Macerate about 20 grams of the sample after mixing with 30 to 40 cc. of
water and strain through muslin. Acidify with 1 or 2 cc. of sulfuric
acid (1 to 3) and extract with ether. (If an emulsion forms, use a
centrifugal machine.) Separate the ether layer and let the ether
evaporate spontaneously and use the residue in the following tests:
Take up a part of the residue with water and taste. If it is very sweet
saccharin is present. Confirm by the following:
_Schmidt’s Test._--Add about 1 gram of sodium hydroxide to another part
of the residue, and heat in an air-oven or oil bath, for half an hour at
about 250° C., to convert the saccharin into salicylic acid. After it
has cooled, acidify with sulfuric acid, extract and test for salicylic
acid with 2 or 3 drops of ferric chlorid solution, letting the solutions
come together slowly. A purple or violet coloration proves the presence
of salicylic acid, which in turn indicates the presence of saccharin.
This test cannot be used if salicylic acid was used as a preservative in
the original product. A test for the acid should first be made.
_Bornstein’s Test._--Heat the remainder of the above ether residue with
resorcin and a very little sulfuric acid till it begins to swell. (It is
best to do this heating in a test-tube.) Let cool till the action stops,
heat again and repeat the operation several times. After cooling the
last time, dilute with water and add sodium hydrate till neutral. If
saccharin is present, there will be a red-green fluorescence.
BENZOIC ACID
Acidify 50 cc. of the sample with sulfuric acid and shake vigorously
with 50 cc. of a mixture of equal parts of ether and petroleum spirit.
Let the liquids separate, then draw off as much as possible of the
solvent and filter. (Use a centrifugal machine if an emulsion forms.)
Separate the extract into 2 parts and evaporate each to dryness over a
small flame and make the following tests:
_Ferric Chlorid Test._--Dissolve one of these residues in ammonia, and
evaporate to dryness on a water-bath. Take up the residue with warm
water, filter, and collect the filtrate in a small test tube. Add a drop
of ferric chlorid solution, and if benzoic acid is present a
characteristic flesh or brownish colored precipitate of ferric benzoate
forms. Sometimes in such products as sweet pickles, a basic ferric
acetate precipitate comes down and the following test had better be
applied.
_Peter’s Method._--Take about 0.1 gram of the second part of the above
ether residue, place in a large test tube (about 50 cc.) and dissolve in
5 to 8 cc. of concentrated sulfuric acid. Add from 0.5 to 0.8 gram of
barium peroxide, a little at a time. Shake each time and cool in water
if necessary. This should produce a permanent froth on the sulfuric
acid. Let stand 25 or 30 minutes, then fill the tube three fourths full
of water, shake and cool rapidly to the temperature of the room, and
filter off the barium sulfate. Extract with chloroform or ether. Remove
the extract and test it for salicylic acid with dilute ferric chlorid.
(See first test under salicylic acid.) In this method salicylic acid
must first be proven absent.
_Mohler’s Test._--Treat the remainder of the second part of the above
ether residue with 2 or 3 cc. of concentrated sulfuric acid. Heat till
white fumes appear. Add a few crystals of potassium nitrate and when
cool dilute with water. Add an excess of ammonia, then a drop or two of
ammonium sulfid. If a red color appears immediately on the surface, it
shows the presence of benzoic acid.
COLORING MATTER IN CATSUPS AND TOMATOES
COCHINEAL
_Girard and Dupre Test._--Shake well a portion of the sample with water
and filter, acidify with hydrochloric acid, then extract with amyl
alcohol, and if cochineal is present the extract will be colored yellow
or orange, the particular shade depending on the amount of cochineal
present. Remove the amyl alcohol and wash with water until it is
neutral. To half of this, add a very dilute solution of uranium acetate,
drop by drop, and shaking well after the addition of each drop.
Cochineal, if present, will produce a characteristic emerald-green
color.
Confirm by adding a drop or two of ammonia to the second half of the
amyl alcohol extract and a violet coloration will be produced if
cochineal is present.
COAL-TAR COLORING MATTER
_Sostegni and Carpentieri Test._--Free from grease a piece of woolen
cloth (nun’s veiling will do) by boiling first in very dilute caustic
soda solution and then in water. Acidify a portion of the sample with 2
to 4 cc. of 10 per cent solution of hydrochloric acid and filter. Strips
of the cleansed cloth are boiled in this filtrate for 5 or 10 minutes,
then removed, washed in water and boiled with very dilute hydrochloric
acid solution. Wash out the acid and dissolve the color from the cloth
by boiling in a solution of ammonium hydroxid (1 to 50). (The time
required will depend upon the dye present.) Remove the cloth from the
solution and acidify the latter with hydrochloric acid and another piece
of the cleansed cloth is immersed and again boiled. This second dyeing
fixes only coal-tar colors on the cloth, hence, no fear of mistaking
them for the natural color of the vegetable.
IN GREEN PICKLES, BEANS, PEAS, ETC.
COPPER SALTS
Burn 20 grams of the sample to an ash and wet the ash with concentrated
nitric acid, dilute with water and boil. Add ammonia till strongly
alkaline and filter. If the filtrate is blue, copper is present.
Confirm by acidifying the filtrate with acetic acid and adding potassium
ferrocyanid. A red or brownish precipitate or coloration proves the
presence of copper. The test for other heavy metals may be made by the
general method given under meats.
IN MIXED PICKLES
TURMERIC
Shake with alcohol to extract the color. Soak a piece of filter paper in
the extract and dry in an air oven at 100° C. Wet the filter paper with
a weak solution of boric acid to which a very little hydrochloric acid
has been added. If turmeric is present, a cherry-red color will appear
when the filter paper is dry.
“SOAKED” VEGETABLES
PEAS, BEANS, AND CORN
There is really no chemical test for this class of foods. Certain
helpful directions given in Bul. 65, p. 54, of the Bureau of Chem., will
assist in identifying such goods. All or nearly all of the green color
of peas and beans is destroyed by the process of “soaking.” They have
the appearance of the well-matured product, and are firm and mealy with
well-formed cotyledons. The process of soaking starts the growth of the
caulicle of the pea. The kernel of corn is plump and hard and does not
have the milky consistency of the immatured product. The characteristic
succulence of the green pea, bean, and corn is absent in the soaked
product.
ALUM IN PICKLES
This is sometimes added to the pickling solution to produce hardness and
crispness.
Burn to ash a sample of the pickles, and, if they are free from copper,
fuse in a platinum dish with sodium carbonate. Extract with boiling
water, and after filtering add ammonium chlorid solution. If alum is
present, a flocculent precipitate will form.
EXAMINATION OF THE CAN OR BOX IN WHICH VEGETABLES ARE SEALED
Generally when the ends of a can are convex, instead of plane or
concave, it is spoiled. In the souring of canned sweet corn, it is
exceptional that the ends are forced outward.
Strike the can and the spoiled cans will give a dull sound while the
good ones will give a distinct tone. Some practice will be necessary to
use this test.
One can judge of the amount of tin dissolved by the corrosion of the
inside of the can.
Reject cans that show much rust around the cap on the inside of the
head.
If more than one hole is found soldered in the cap, reject the can. Cans
of salmon are the only exception that has come to the author’s notice. A
second hole, in general, indicates that decomposition had set in and the
can had been punctured and resealed.
CHAPTER VI
FRUITS AND FRUIT PRODUCTS
Salicylic acid, benzoic acid, and saccharin are used to preserve fruits.
The last is also added as a sweetener instead of sugar. Many fruit
products lose their color with age, and to give them a lasting color
they are treated with a coal-tar dye, cochineal, acid magenta, or
caramel.
A very small per cent of the jams and jellies sold are strictly pure.
These cheap products are made up principally of apple juice and
commercial glucose; artificial essences are added to imitate the real
flavor.
In cheap jellies made of apple juice and glucose syrup, a “coagulator”
is used; usually sulfuric acid and alum, also citric and tartaric acids
may be used for this purpose.
Starch, gelatin, and agar are used as gelatinizing agents.
Fruits put up in tin cans may dissolve the heavy metals as tin, zinc,
lead, and even arsenic.
PRESERVATIVES
_Preparation of the Sample._--Dissolve 25 or 30 grams of the sample in
water which has been acidified with sulfuric acid (1 to 3), then extract
with ether, and remove the ether layer and let it evaporate
spontaneously. The residue may contain salicylic acid, benzoic acid, or
saccharin. Take up with a little water and make the following tests:
SALICYLIC ACID
Place a few drops of this extract in a test tube and add a drop or two
of a 0.5 per cent solution of ferric chlorid. If salicylic acid is
present, there will be a purple coloration.
BENZOIC ACID
_Mohler’s Test._--Add 2 to 3 cc. of strong sulfuric acid to a second
portion of the above ether extract and heat until white fumes appear.
Then add a few crystals of potassium nitrate and heat again. Continue
adding the nitrate and heating till the solution is colorless or only a
very light yellow. Dilute with about 5 cc. of water when cool,
neutralize with ammonia. It should be filtered when not clear or when
crystals of ammonium or potassium sulfate are formed. Add a few drops of
ammonium sulfid to the filtrate in such a way as to prevent the mixing
of the liquids. The sulfid will be on top. If a bright cherry-red color
forms where the two liquids meet, either benzoic acid or saccharin is
present. Distil and the benzoic acid will pass over, extract the
distillate in the usual way and apply the above test to it for benzoic
acid.
SACCHARIN
Taste a third portion of the ether extract. A very sweet taste indicates
saccharin. A further test can be made by adding 1 or 2 grams of sodium
hydroxid to the rest of the ether extract and heating a half hour in an
oil bath at 250° C. Dissolve in water when cool, acidify with dilute
sulfuric acid and extract with ether. The saccharin will have been
converted into salicylic acid, which may be identified by the usual test
for that acid. This test presupposes the absence of salicylic acid in
the original material.
COLORING MATTER
COAL-TAR DYES
To attempt to identify the particular dye used in every case would be
quite beyond the object of this set of simple tests. A general test
showing the presence of a coal-tar dye is probably all that is usually
desired.
_Sostegni and Carpentieri Test._--Such a test may be made by dissolving
15 grams of the fruit product in 100 cc. of water, filtering and
acidifying with a small quantity of a 10 per cent solution of
hydrochloric acid and again filtering. Place in the filtrate strips of
white woolen cloth (nun’s veiling will do) which have been freed from
grease by boiling first in very dilute caustic soda solution, then in
water, and boil for 5 to 10 minutes. Remove the cloth and wash it in
water, then boil in very dilute hydrochloric acid. Stir the cloth in
water to remove the acid and dissolve the color by boiling in a solution
of ammonium hydroxid (1 to 50). The time required will depend upon the
particular dye used. Remove the cloth from the solution and acidify the
latter with hydrochloric acid, a slight excess is better, and another
piece of the cleansed cloth is immersed and again boiled. Nothing but
coal-tar dyes will color in this second dyeing.
COCHINEAL
_Girard and Dupre Test._--See tests for cochineal under “Catsups and
tomatoes.”
ACID MAGENTA
_Girard and Dupre._--Make about 100 cc. solution of the fruit, filter,
and neutralize with potassium hydroxid (strength 5 to 100); about 2 cc.
will be needed. Add 4 cc. of mercuric acetate solution (1 to 10), shake
and filter. By this treatment the filtrate should be colorless and
slightly alkaline. Add sulfuric acid till there is a slight excess. A
colorless solution indicates the absence of acid magenta, while a light
violet-red shows its presence, providing the amyl-alcohol extract showed
no other dye to be present.
CARAMEL
_Amthor’s Test._--10 cc. of a solution of the fruit is put into a deep,
narrow glass (a bottle may be used). Add 30 to 50 cc. of paraldehyde, to
be gaged by the intensity of the coloring. Then add a sufficient
quantity of absolute alcohol to make the solutions mix. If caramel is
present, a brownish-yellow to dark-brown precipitate will be formed,
decant, wash the precipitate once with absolute alcohol, dissolve in a
little hot water and filter. The shade of color is proportional to the
amount of caramel present.
To verify the test, pour the colored fluid into a freshly prepared
solution of phenylhydrazin (2 parts phenylhydrazin-hydrochlorid, 3 parts
sodium acetate, and 20 parts water). Much caramel produces a dark-brown
precipitate in the cold, and is hastened by slightly heating. A very
small amount of caramel will require several hours to precipitate.
APPLE-JUICE IN JELLIES MADE OF SMALL FRUITS
Very often cider is added to other fruit juices to give them the proper
consistency in jellies, jams, and marmalades.
Its presence may some times be determined by making the usual starch
test. A large quantity of starch is normally present in apples, but is
less as they ripen, and finally disappears in the ripened fruit. There
is no starch, or only a mere trace, in small fruits even when green. It
is readily seen that if the juice is taken from green apples that there
will be starch found in the artificial jelly or jam, though its absence
does not prove the absence of cider.
Make the starch test as follows:
STARCH
IN JELLIES, JAMS, AND SUCH PRODUCTS
Make a solution of the jelly or jam and destroy the color by heating
nearly to the boiling point and adding dilute (1 : 3) sulfuric acid and
potassium permanganate until the color is destroyed. This treatment does
not affect the starch, and when cool add iodin, preferably potassium
iodid-iodin (potassium iodid, 0.4 gram; iodin, 0.1 gram; water, 20 cc.).
If a great quantity of starch is present an almost black precipitate
will be formed. Smaller amounts give the usual blue color.
Whenever starch is found to be present, it is best to make a
microscopical examination in the case of jams and marmalades. If the
starch is normally present the grains will be seen within the cell walls
after the iodin treatment.
Starch is nearly always present in the apple and some other fruits, so
unless it is present in jelly and such products in considerable quantity
it is not likely that it was added.
GELATIN
IN JELLIES
_Henzold Test._--Add water to some of the jelly and boil for a short
time, filter and treat the filtrate with an excess of a 10 per cent
solution of potassium bichromate and boil again. After cooling add 2 or
3 drops of concentrated sulfuric acid. A white flocculent precipitate
forms if gelatin is present, and it gradually collects in a lump at the
bottom.
_E. Beckmann’s Method._--Treat the jelly with 95 per cent alcohol and
wash the precipitate with alcohol to free it from the sugar, then drive
off the alcohol by heating. Add a very little water to the residue and
neutralize the extract with calcium carbonate. Then add formalin and
evaporate to dryness. By this treatment gelatin is rendered insoluble.
Pure fruit jellies have only 1 to 2 per cent of insoluble precipitate,
while those jellies in which gelatin is used have 70 to 86 per cent of
insoluble precipitate.
AGAR AGAR
Boil the sample with 5 per cent sulfuric acid. Add a crystal or two of
potassium permanganate, and wait till it settles, and examine the
sediment for diatoms with a microscope. Their presence shows the use of
agar.
HEAVY METALS
TIN, ZINC, LEAD, AND COPPER
_A. H. Allen’s Method._--(See test for heavy metals under canned meat.)
ARSENIC
_Marsh’s Test._--Fit a 100 cc. flask with a two-holed rubber stopper,
through which passes a long-stemmed separatory funnel reaching nearly to
the bottom, and a delivery tube which connects with a bulb tube
containing a little acetate of lead solution. This in turn is connected
with a calcium chlorid tube and this with a small, hard glass tube, 15
or 20 cm. long, not over 0.5 cm. bore, and drawn to small size in the
middle. The large part next the chlorid tube is protected by fine wire
gauze which extends to within a half inch of the constricted part. Two
burners may be so placed as to heat the gauze. The flask should be
placed in water and the bulb tube may be. Four grams of arsenic-free
zinc, and 40 cc. of dilute pure sulfuric acid (1 to 8) are placed in the
flask. Let the hydrogen flow at least a quarter of an hour, then heat
the gauze for 15 or 20 minutes. There should be no deposit in the tube.
Now, char a portion of the sample, dissolve in water and pour into the
separatory funnel, letting it run slowly into the flask. A dark deposit
in the glass tube shows that arsenic is present, but if after an hour no
darkening takes place it is quite safe to say that no arsenic is present
in the fruit.
[Illustration: Apparatus for Marsh Test]
_Gutzeit’s Test._--Place a gram of pure zinc, 5 cc. of dilute sulfuric
acid (6 per cent) and about 1 cc. of a solution of the sample in a deep
test tube. Cover the tube with three thicknesses of filter paper, fitted
tightly over the mouth of the tube. Place on the upper paper a drop of
strong silver nitrate solution. Place the tube in a dark place and leave
for 10 minutes. If a bright yellow stain forms on the filter paper, and
turns black or brown when water is added to it, arsenic is present.
Unless one is certain of the purity of the reagents used it is advisable
to make a blank test, using distilled water instead of the fruit.
Oxidize all sulfids to sulfates before applying the above test. To find
out whether they are present or not, substitute lead acetate for the
silver nitrate on the filter paper. To avoid some of these difficulties
treat according to the following method:
_Preparation of the sample according to Leach._--If possible reduce the
sample to a dry char by treatment with concentrated nitric and sulfuric
acids so that it may be powdered in a mortar. Dissolve out the arsenic
by repeated treatment with boiling water. Save this extract, and, when
cool, filter and submit to Marsh’s test which is given above.
In case the sample is too much of a solid to get the arsenic out by the
above treatment, it may be prepared according to the directions of
Chittenden and Donaldson: Heat 100 grams of the macerated sample with 23
cc. of pure, strong nitric acid to a temperature of 150° C. or 160° C.
Assist the action by stirring occasionally. When the fruit becomes a
deep yellow or orange color, remove the heat and add 3 cc. of pure,
strong sulfuric acid. It should be stirred while nitrous fumes are
passing off. Heat again to about 180° C., and before it cools add, drop
by drop, 8 cc. of pure concentrated nitric acid. It should be stirred
constantly while the acid is being added. Heat at 200° C. till sulfuric
acid fumes begin to come off and only a dry mass remains. Powder the
mass and exhaust it with boiling water, filter and test the solution
when cold with Marsh’s test.
CHAPTER VII
FLAVORING EXTRACTS
LEMON EXTRACT
The important ingredients of lemon extract are lemon oil and citral, its
aromatic constituent. Oil of citronella and oil of lemon grass are
sometimes substituted for lemon oil. Methyl alcohol is sometimes used in
place of the more expensive spirit alcohol as a solvent for the lemon
oil.
LEMON OIL
The presence of lemon oil may be detected by adding a large excess of
water to a small amount of the extract in a test tube. If the mixture
does not show some cloudiness, it is a strong indication that no lemon
oil is present. The degree of cloudiness gives an idea of the amount of
oil present.
CITRAL
This is present in the oil of lemon grass, which is sometimes used as a
substitute for lemon oil. Citral may be detected by the following test
by Burgess:
Add 20 cc. of sulfuric acid to 85 cc. of water. Dissolve in this mixture
10 grams of mercuric sulfate. Shake 2 cc. of the sample with 5 cc. of
this reagent in a test tube. If citral is present, the liquid will be
bright red, and will quickly disappear and give place to a whitish
compound, which floats on top.
OIL OF CITRONELLA
This is often substituted for lemon oil. It may be detected by the same
test which was used for citral. Instead of the red color and the white
compound, citronella gives a bright yellow color, which does not
disappear for some time.
TARTARIC OR CITRIC ACID
Precipitate the oil by the addition of an equal volume of water. Filter
and add a very little of the filtrate to a test tube nearly full of cold
lime water. A precipitate will form if tartaric acid is present and it
will dissolve in an excess of ammonium chlorid or acetic acid. Filter,
or, in case no precipitate forms, heat the liquid. Citric acid is
precipitated in the presence of a large excess of hot lime water.
METHYL ALCOHOL
_Mullikin and Scudder._--Take 2 ft. of No. 12-15 copper wire and bend at
right angles about 8 or 10 inches from one end. Grasp this bent end and
an ordinary lead pencil side by side in such a way that the bend will be
about the middle of the pencil. Wind the wire around the pencil and
toward the free end of the short part of the wire until you have a coil
3 or 4 cm. long. Remove the pencil and twist the unwound parts together
for a handle for the coil.
Dilute a portion of the sample 3 or 4 times, and oxidize 10 cc. of the
diluted liquid (preferably in a test tube) by heating to a red heat the
above copper coil in the oxidizing flame of a Bunsen lamp. Thrust the
heated coil quickly into the liquid contained in the test tube. In a
second withdraw and immerse in water. Continue this operation till the
oxid of copper fails to be reduced (usually 4 or 5 times is sufficient).
Cool the liquid by immersing the tube in water. Separate into two parts
and test each for formaldehyde by the following methods:
_Mullikin, S. P._--Place one of these parts in an evaporating dish, and
add to it 1 cc. of strong ammonia, boil gently over the free flame till
the vapors cease to smell of ammonia. Add 2 or 3 drops of strong
hydrochloric acid and heat just to boiling, and cool quickly by dipping
the dish in cold water. Make the test for formaldehyde: Add a drop of a
solution of resorcin (1 : 200) and pour this mixture slowly down the
side of an inclined test tube which contains 3 cc. of strong sulfuric
acid, taking care to keep the liquids separate. After 3 minutes give the
tube a rotary motion by rolling between the hands for a minute or more
but only gradually mixing the water and acid, but mixing only about half
of the acid.
Flecks of a rose-red color form if methyl alcohol is present. Bands of
color or flecks of other colors, even though they be tinged with red or
a rose-red solution without the precipitate, should never be taken as
proof that methyl alcohol is present. These conditions, however, are
good grounds for repeating the test; 10 per cent or even less may be
detected by this test.
_Hydrochloric Acid and Ferric Chlorid Test._--Add a few drops of the
other part of the above oxidized liquid to about 10 cc. of milk, known
to be free from formaldehyde, in a porcelain casserole, and add 10 cc.
of commercial hydrochloric acid (sp. gr. 1.2) which contains 1 cc. of 10
per cent ferric chlorid per 500 cc. Heat slowly over the open flame
nearly to boiling. Give the liquid a rotary motion to break up the
curd. If formaldehyde is present, the liquid will be colored violet. If
not, it slowly turns brown. The presence of formaldehyde proves that
methyl alcohol was in the original extract.
COLORING MATTER
_Preliminary Test._--Treat the sample with strong hydrochloric acid, and
if tropæolin or methyl orange be present the solution will turn pink;
Martius yellow partially decolorizes the solution; dinitrocresols
decolorizes the solution. Turmeric or naphthol yellow produces no color
change.
TURMERIC
Turmeric may be detected by soaking a piece of filter paper in the
sample, drying and dipping it in a dilute solution of boric acid or
borax which has been slightly acidulated with hydrochlorid acid. Dry
again and a cherry-red color forms if turmeric is present. Add a drop of
dilute alkali and if turmeric be present the paper will be colored dark
olive.
COAL-TAR COLORS
Evaporate some of the extract to dryness; take up the residue with water
and extract the coal-tar colors if present, and test for them by the
method given under canned vegetables.
VANILLA EXTRACTS
The best grades of vanilla extract are made by treating vanilla beans
with 50 per cent alcohol. Coumarin, an extract from tonka beans, may be
used in making the extract. This of course would make a cheaper product.
If less than 50 per cent alcohol is used in making the extract, some
alkali must be added to dissolve the resins which will not dissolve in
a weaker alcohol. In artificial extracts some such coloring matter as
caramel or tannin is used.
_Preliminary Test._--To a portion of the extract add a few drops of lead
acetate solution. The absence of a bulky flocculent precipitate shows
the extract not to be of high quality. Leach recommends that normal
acetate of lead be added to the sample, and if a precipitate does not
form it is conclusive evidence that it is not a pure extract.
When a precipitate forms with the above reagent, it should settle
immediately and leave a clear and almost colorless liquid. When there is
a mere cloudiness only, it may be due to caramel, in which case the
extract is to be suspected.
ALKALI
Shake a portion of the sample with twice its volume of water. If no
precipitate forms, an alkali is present. A flocculent reddish-brown
precipitate shows no alkali is present. If the solution is milky it
indicates the presence of a foreign resin.
Add hydrochloric acid drop by drop to the diluted extract. Nothing more
than a mere turbidity should result. Should it be quite turbid and the
color fading after a time, it shows that an alkali has been used.
FOREIGN RESINS
Mix a portion of the extract slowly with twice its volume of water,
frequently shaking the mixture. When this solution is milky, it
indicates a foreign resin.
_Hess’ Test._--Dealcoholize 25 cc. of the sample by concentrating on the
water-bath, adding water from time to time to retain the original
volume. When no alkali is present in the extract, pure vanilla resin
will be thrown down as a reddish-brown flocculent precipitate. Collect
the resin, whatever its color, on a filter, and wash. Save the filtrate
to test for caramel. Place a piece of the paper and resin in a dilute
solution of potassium hydroxid. If the resin is that of pure vanilla it
will dissolve, giving a deep-red color, and is reprecipitated when the
alkali is neutralized with hydrochloric acid. Dissolve another part of
the precipitate in alcohol, and to a part of this solution add a few
drops of ferric chlorid; and to the other part, hydrochloric acid. There
should be no marked coloration in either case if the resin is that of
pure vanilla. Foreign resins nearly always produce a coloration.
CARAMEL
Shake the bottle of vanilla, and if the bubbles, which form, are a
bright caramel color, keeping the color till all are gone, the presence
of caramel is indicated.
Concentrate a portion of the filtrate, which was saved in making the
test for foreign resins, at a rather low temperature until it has about
the same color as the original extract. Add a few drops of strong
hydrochloric acid and heat very gently. If caramel is present, a
yellowish-red flocculent precipitate will form. After the liquid cools,
filter and wash with water. Should this precipitate contain caramel, it
will not dissolve in water, ether, and alcohol, but will dissolve in
sodium hydroxid, dilute alcohol, and glacial acetic acid.
TANNIN
Test another portion of the filtrate made in testing for foreign resins,
with a few drops of a solution of gelatin. A slight precipitate only
should form due to the presence of a small amount of tannin normally
present in this filtrate. A large excess shows that it has been added to
the extract.
COUMARIN
_Leach’s Test._--Dealcoholize a portion of the sample as above and treat
with ammonia, add 3 or 4 volumes of chloroform in a separatory funnel.
Evaporate the chloroform extract in an oven, not permitting the
temperature to rise above 60° C. To the residue add a few drops of
water; warm gently, and add a little of a solution of 1 gram of
crystallized potassium iodid in 50 cc. of water, and the solution
saturated with iodin. If coumarin is present, a brown, precipitate will
form, and if stirred with a rod it will collect in dark green flecks.
CHAPTER VIII
SACCHARINE PRODUCTS
HONEY
Bees are sometimes fed with cane sugar. Often glucose syrup is poured
over honeycomb from which the honey has been extracted, and the mixture
sold as genuine honey.
Gelatin may be added to increase the weight or to thicken the more
voluble adulterants.
The ash of genuine honey is not over 0.3 per cent. Whenever the ash is
greater than this it should be tested for calcium sulfate, the presence
of a considerable quantity of which is an almost certain proof that
starch glucose or invert sugar has been added to the honey. Sulfates may
be detected by adding barium chlorid to the aqueous solution of the
honey and precipitating barium sulfate.
If the ash is high and considerable chlorids are present, molasses has
quite probably been added to the honey. The presence of chlorids may be
determined by the addition of silver nitrate which precipitates silver
chlorid.
CANE SUGAR
The presence of cane sugar can be detected with certainty only by the
use of the polarimeter. Its presence in large quantity gives a high
right-handed rotation.
COMMERCIAL GLUCOSE SYRUP
_Allen’s Test._--Make the test for dextrine which is present in
commercial glucose, but not in pure honey. Dilute a portion of the honey
with an equal volume of water and add methyl alcohol with constant
stirring until there is a permanent turbidity. If glucose syrup is
present a heavy gummy precipitate will soon form. Genuine honey gives
only a slight milkiness.
GELATIN
Dilute a portion of the sample and add a solution of tannic acid. A
precipitate indicates the presence of gelatin.
Treat the sample with alcohol, and gelatin, if present, will be left
undissolved, and it will give its characteristic odor on ignition.
MAPLE SYRUP
This is sometimes adulterated with glucose, molasses, golden syrup, and
with ordinary white sugar. There are no satisfactory simple chemical
tests for these substances.
Pure maple syrup should have an ash not lower than 0.35 to 0.40 per
cent. A lower ash shows that cane sugar has been added. A higher ash
would indicate the presence of molasses or brown sugar stock. These last
two adulterants, if present in great abundance, may be detected by
taste.
GLUCOSE
This may be detected by the use of the polarimeter. Pure maple syrup
gives 53.1 to 60 direct, and--22.2 to--21.9 after hydrolysis. Maple
syrup adulterated with glucose gives 80 to 100 direct and 18.9 to 45.6
after hydrolysis (according to Ogdon).
CHAPTER IX
SPICES
MUSTARD
Mustard is often adulterated with mustard hulls, wheat, and rice. And
when white-colored flour of any kind is used, turmeric, Martius yellow,
or a coal-tar color is employed to give the mixture the color of
mustard. Cayenne pepper is occasionally used to impart pungency to
diluted mustard.
FLOUR
Boil 2 grams of the mustard in 4 or 5 cc. of distilled water for about
10 minutes. After it is cool, add a few drops of iodin solution slowly,
avoiding a large excess though having a little uncombined iodin. If a
blue color is produced, some starchy matter has been added to the
mustard. The intensity of the reaction is an indication of the amount of
starchy matter used. Pure mustard contains no starch and hence gives no
reaction with iodin.
COLORING MATTER
Pure mustard is a very light dull yellow, and whenever the sample is
bright yellow, there is good grounds for suspecting the presence of some
artificial coloring matter.
TURMERIC
Add strong ammonium hydroxid to the mustard, and if turmeric is present
an orange-red color is usually produced.
Make an alcoholic extract of the sample and dip a piece of filter paper
in it, and when dry draw it through a cold, saturated solution of boric
acid in water. An orange or red-brown tint produced on the paper
indicates the presence of turmeric.
Thoroughly mix 2 or 3 grams of the mustard with castor oil and filter.
If turmeric is present the filtrate will appear fluorescent.
Extract a portion of the sample with 3 times its weight of wood alcohol
and filter. Evaporate one half of the solution to dryness and add a
little hydrochloric acid to the residue. This will turn red whenever
turmeric is present, and if an excess of alkali be added it will change
to a greenish blue. Evaporate the other half to dryness and moisten with
a solution of boric acid and dry on a steam bath. A cherry-red color
indicates turmeric.
MARTIUS YELLOW OR ANALOGOUS COAL-TAR COLORING MATTER
Extract the slightly acidified sample with 95 per cent alcohol and dye
wool as directed under “Vegetables.” The wool will be dyed a bright
yellow.
_Allen’s Test._--Treat a portion of the sample with cold alcohol, and
shake vigorously for 5 minutes, then filter and evaporate the filtrate
to dryness; add enough water to take up the residue and dye some white
wool in this liquid as in the last test. When the dyed wool is wrapped
in white paper and heated to 120° in an air bath, part of the coloring
matter will be transferred to the paper. The coloring matter dissolves
readily in dilute ammonia or hot water, and on the addition of
hydrochloric acid the solution is decolorized and a yellow precipitate
formed. This distinguishes it from picric acid.
CAYENNE PEPPER
_Allen’s Test._--Boil 1 gram of the mustard for a few minutes with
alcohol, filter, and evaporate to dryness at about 100°. Taste the
residue and cayenne may be recognized by its pungency. Or heat a portion
of the extract, and smell the fumes. Irritation of the lungs and
coughing will surely follow if cayenne pepper is present.
PEPPER
Pepper may be adulterated with wheat, buckwheat, pepper husks, ground
olive stones, spent ginger. Cayenne pepper is sometimes added to
adulterated pepper to give it the normal pungency. Many of these
adulterants can be detected only by the aid of the microscope.
_Neuss’s Test._--True pepper turns an intense yellow when covered with
strong hydrochloric acid. Any adulteration can be detected at once by
the color.
GROUND OLIVE STONES OR “POIVRETTE”
Make a paste of the pepper with caustic alkali. Dilute with a large
quantity of water and wash by decantation. Olive stones will be colored
a bright yellow; pepper-husks will appear dark.
_Jumeau’s Test._--Dissolve 5 grams of iodin in a mixture of 50 cc. of
ether and 50 cc. of alcohol. Cover the bottom of a porcelain capsule
with the finely ground pepper, and add just enough of the iodin mixture
to wet the entire mass, and mix well till it has the same consistency
throughout. Let dry in the air, then powder and examine it, and if olive
stones are present they will be colored yellow. Pure pepper would have a
deep brown color.
Aniline acetate, one part aniline in 3 parts acetic acid, colors pure
pepper gray or white and olive stones yellowish brown.
CAYENNE
Heat some of the red particles found in the pepper and their
characteristic vapor is produced. Dissolve the particles in alcohol or
ether and the same vapors are produced.
CHAPTER X
VINEGAR
Vinegars may be adulterated by the addition of mineral acids as sulfuric
or hydrochloric. Caramel or the coal-tar dyes may be employed to improve
the color or to give color to an artificial product. Malic acid is
always present in cider vinegar. Potassium acid tartrate occurs in true
wine vinegar. Poisonous metals may be present in vinegars containing
free mineral acid. Entirely artificial cider vinegar is often found on
the market.
PREPARATION OF THE SAMPLE FOR TESTING
If the vinegar is turbid from any suspended matter, it should be
filtered. The samples should be analyzed at once, and in the laboratory
they should always be kept in glass-stoppered bottles.
_General Observations._--Ignite a little of the vinegar residue on a
clean platinum wire in a colorless Bunsen flame, and if it is pure cider
vinegar the flame will be colored the characteristic lilac color of
potassium. The sodium flame is absent or only a mere trace of it is
present. But in all artificially colored vinegars, spirit sugar and
glucose vinegars, the sodium flame predominates.
The residue of cider vinegar is thick, viscid, or mucilaginous, of a
light brown color, astringent acid taste though not unpleasant. The
solids of sugar-house vinegar, those from colored spirit and wood
vinegar, each have a bitter taste on account of the caramel used to
color them. The residue of the sugar-house vinegar has the odor of
molasses. Wood vinegar when present gives a residue with a tarry or
smoky taste and smell. Glucose vinegar gives the odor of scorched corn.
Solids of fruit vinegars are quite soluble in alcohol, except a granular
residue in grape vinegar, while the solids of malt and glucose vinegars
are almost insoluble.
The ash of fruit vinegars and malt vinegars has a distinct alkaline
reaction, while that of spirit and wood vinegars is very feebly
alkaline.
FREE MINERAL ACIDS
The ash of pure cider vinegar is always alkaline. If a vinegar should
show a neutral reaction this would certainly indicate the presence of a
free mineral acid. If the ash be alkaline, no acid except nitric could
have been present, and this is seldom, if ever, used as an adulterant of
vinegar.
WHEN THE ASH IS ALKALINE APPLY
_Ashby’s Test._--Extract 0.5 gram of logwood in 100 cc. of water and dry
a drop or two on a porcelain surface. Then add a drop of the vinegar and
dry again. If the residue is red, a mineral acid is present; if yellow,
mineral acids are absent. When only a very small amount of the acid is
present the red coloration will be destroyed on diluting with water, but
may be restored by concentrating the liquid.
SULFURIC ACID
Sulfuric acid, if present, will cause the vinegar to leave a charred
mass when evaporated over the water-bath.
_Frear’s Method._--Mix 5 cc. of the sample and 5 or 10 cc. of water, and
add a very little of a solution of methyl violet (made by dissolving one
part of methyl violet 2 B. in 100,000 parts of water). A blue or green
coloration shows the presence of mineral acids.
SULFURIC ACID AS DISTINGUISHED FROM SULFATES
_Allen’s Method._--Evaporate 100 cc. of the vinegar down to one tenth
its volume, and when cold add 50 cc. of alcohol. Sulfuric acid remains
in solution while the sulfates are precipitated. Dilute the solution and
precipitate the acid with barium chlorid.
HYDROCHLORIC ACID
FREE
Place a definite quantity of the vinegar in a distilling flask and
distil off half. Add a few drops of silver nitrate to the distillate. If
a precipitate forms, hydrochloric acid is present.
MALIC ACID
_Leach’s Method._--To 5 cc. of the sample, add a few drops of a solution
of calcium chlorid (1 : 10); make slightly alkaline with ammonia. Filter
off any precipitate that may form, add 20 to 30 cc. of 95 per cent
alcohol to the filtrate and heat to boiling. If malic acid is present, a
voluminous flocculent precipitate will form. A precipitate may form in
vinegars containing dextrine. Make a further test for malic acid by the
following: Filter and treat the precipitate with a little alcohol, and
when dry add concentrated nitric acid and evaporate to dryness on a
water-bath. Treat the residue with sodium carbonate, boil for a short
time, filter. Add acetic acid to the filtrate till slightly alkaline,
boil till carbon dioxid is expelled, and if on the addition of calcium
sulfate a precipitate forms, it indicates the presence of malic acid.
COLORING MATTER
CARAMEL
The residue of vinegar to which much caramel has been added has an
unusually dark color and bitter taste.
_Crampton and Simons’ Method._--Shake well together in a corked flask 50
cc. of the vinegar with about half as many grams of fullers’ earth;
after standing for half an hour filter. Vinegar containing no artificial
color will show scarcely any change in color when thus treated. A
caramel-colored vinegar will be decolorized in proportion to the amount
of caramel present.
COAL-TAR COLORS IN WINE VINEGAR
Test by the usual test for coal-tar dyes. See under canned vegetables.
METALLIC IMPURITIES
Vinegars containing free mineral acids are sometimes found to contain
poisonous metals.
Evaporate 200 to 400 cc. of the vinegar to dryness, add a little sodium
hydroxid to this residue and burn to an ash over a low flame. It may be
necessary to add a little potassium nitrate once or twice. Add a little
dilute hydrochloric acid and saturate with hydrogen sulfid and test for
lead, zinc, copper, and arsenic according to Allen’s method given under
canned meats.
SPICES TO INCREASE PUNGENCY
_Leach._--Neutralize a portion of the vinegar with sodium carbonate. The
presence of spices is easily detected by tasting this mixture.
_Another Test._--Exactly neutralize a little of the vinegar as above,
evaporate to smaller bulk and taste as before, then shake the
concentrated liquid with ether, separate the ethereal layer and
evaporate it, and taste the residue.
TARTAR IN WINE VINEGAR
The presence of tartar in vinegar proves it to be wine vinegar.
_Allen’s Method._--Evaporate a portion of the vinegar and treat the
residue with alcohol; a granular residue of tartar remains undissolved.
To prove that it is tartar, decant the alcohol and dissolve the residue
in a little hot water, cool, rub the inside of the vessel with a glass
rod, and if tartar was present acid potassium tartrate will be deposited
where the rod touched the vessel. The test will be more sensitive if an
equal volume of alcohol is added.
FREE TARTARIC ACID IN WINE VINEGAR
_Test as for Tartar._--Treat the alcoholic solution of the extract with
an alcoholic solution of potassium acetate. Rub the sides of the vessel
as before, and if tartaric acid is present the streaks and sometimes a
precipitate forms where the rod touches the vessel.
GLUCOSE
Glucose is present when both direct and invert readings are
dextro-rotatory.
CHAPTER XI
FATS AND OILS
LARD
Lard is very often adulterated with cottonseed oil, cottonseed stearin
and beef stearin. Their being very much cheaper accounts for the
sophistication.
COTTONSEED OIL
_Halphen’s Test._--Dissolve 1 per cent of sulfur in a given volume of
carbon bisulfid. Add an equal volume of amylic alcohol. Mix 3 to 5 cc.
of this reagent with an equal volume of the melted lard in a test tube.
Close with a cotton stopper and boil for 15 minutes in a bath of
saturated brine. The presence of cottonseed oil is indicated by a
deep-red or orange color, little or no color resulting in its absence.
Lard from hogs fed on any of the various cottonseed products may give a
faint reaction when this test is applied.
COTTONSEED STEARIN
Since cottonseed stearin is only the more solid portions of cottonseed
oil, the above test may be applied, but to distinguish it from the
latter it is necessary to make determinations quite beyond the scope of
this set of tests.
BEEF-STEARIN
It is very difficult to identify beef-stearin by chemical tests. It is
usually detected by use of the microscope. Leach gives the following
method: Make a solution of 2 to 5 grams of the fat in 10 to 20 cc. of
ether. Let stand a half day, at about the room temperature. Loosely
stopper the tube with cotton to prevent too rapid evaporation of the
ether. It is well to vary the conditions of heat, amount of solvent, and
rate of crystallization, to get the best possible results. It may often
be well to separate the crystals thus obtained by filtering and
recrystallizing from ether. Separate the crystals that form at the
bottom of the test tube from the liquid portion by pouring on a small
filter. Wash them several times with ether, but not sufficient to remove
the mother liquor entirely. In case it is all removed, and the crystals
are too fragile to mount, add a drop of alcohol. Crystals of lard
stearin are flat rhomboidal plates, one end being oblique to the sides,
and they do not appear to be regularly grouped. Beef-stearin crystals
are rod-shaped, or needles often apparently curved with pointed ends,
and are arranged in clusters like the ribs of a fan, the crystals
radiating from a common point. Under certain conditions the lard
crystals are not irregularly grouped, but are arranged like the parts of
a feather, where one part seems attached to another close at hand.
Considerable experience is necessary to use this test with absolute
certainty.
OLIVE OIL
Olive oil is one of the most commonly adulterated foods. The commonest
adulterant probably is cottonseed oil. Other foreign oils, such as
peanut, sesame, and rape, are sometimes used.
_Preliminary Test._--Pure olive oil turns from a pale to a dark-green
color in a few minutes, when it is shaken with the same volume of
concentrated nitric acid or sulfuric acid. Whenever a reddish to an
orange, or brown coloration results, the presence of a foreign vegetable
oil is indicated (probably a seed oil).
Bach gives the following results of strong nitric acid on the common
oils. Olive oil when shaken with nitric acid gives a pale green, which
changes to an orange yellow after heating five minutes. With similar
treatment peanut oil gives pale rose and brownish yellow; rape oil, pale
rose and orange yellow; sesame oil, white and brownish yellow; sunflower
oil, dirty white and reddish yellow; cottonseed oil, yellowish brown and
reddish brown; castor oil, pale rose and golden yellow.
_Pontet’s Test; Elaiden Test._--Treat 1 cc. of mercury with 12 cc. of
cold nitric acid (sp. gr. 1.42) and shake 2 cc. of this freshly-made
solution with 50 cc. of the sample in a bottle every 10 minutes for 2
hours. Oils which are principally olein, or mixtures of olein and solid
esters like palmatin and stearin, give more or less solid products, but
olive oil is remarkable for the firmness of the canary or lemon-yellow
mass which is formed. After standing a day the mass cannot be pierced
with a glass rod and sometimes it gives forth a sound when struck.
This test requires considerable experience to be used with any great
degree of certainty.
COTTONSEED OIL
Carbon bisulfid containing 1 per cent of sulfur in solution is mixed
with an equal amount of amyl alcohol. Equal volumes (about 3 cc.) of
this reagent and the sample, are mixed in a test tube, which is loosely
stoppered with cotton, and heated in a bath of boiling saturated brine
for a quarter of an hour. The presence of cottonseed oil is shown by the
formation of a deep-red or orange color. Little if any color is produced
in its absence. If no color is produced it is well to add another cc. of
the reagent and heat 5 or 10 minutes more, and to repeat this again if
no color forms. Lard and lard oil from animals fed on cottonseed meal
may give a faint reaction.
PEANUT OIL (ARACHIS OIL)
_Bellier’s Test._--Saponify a gram of the sample with 5 cc. of a
solution of 85 grams potassium hydroxid in a liter of strong alcohol.
This may be done in a small Erlenmeyer flask on the water-bath. Then
boil for two minutes, neutralize exactly with dilute acetic acid (use
phenolphthalein as the indicator). Cool the mixture by placing the flask
in water at 17° to 19° C. A precipitate usually forms. Add 50 cc. of 70
per cent alcohol which contains one per cent by volume of concentrated
hydrochloric acid (sp. gr. 1.2). Shake the flask vigorously and cool
again as before. If no precipitate forms the oil is not adulterated with
peanut oil. The presence of 10 per cent or more of peanut oil produces a
precipitate, even a smaller amount will produce a cloudiness after
standing between 17° and 19° C. for 30 minutes.
Some varieties of olive oil from Tunis give the same turbidity when the
70 per cent alcohol is added. To distinguish these from peanut oil heat
the mixture on the water-bath till everything has dissolved, and cool to
17° to 19°. The cloudiness will not appear if the oil is pure, but will
reappear if peanut oil is present.
SESAME OIL
_Badouin’s Test._--About 0.1 of a gram of cane sugar is dissolved in 10
cc. of hydrochloric acid (sp. gr. 1.20) shaken vigorously with 20 grams
of the sample for a minute or more. After standing for a while the
aqueous solution will separate from the oil. If 1 per cent or more of
sesame oil is present, the aqueous solution will be colored crimson.
_Tocher’s Test._--Dissolve 1 gram of pyrogallic acid in 15 cc. of strong
hydrochloric acid. Add an equal volume of the oil in a separatory
funnel. When it has stood a minute, draw off the aqueous solution and
boil. In the presence of sesame oil it is colored red by transmitted
light, and blue by reflected light.
RAPE OIL
_Palas’ Test._--Make a 1 per cent solution of fuchsin and a 30 per cent
solution of sodium acid sulfite. Mix together 20 cc. of each of these
solutions and add 200 cc. of water and 5 cc. of strong sulfuric acid.
After the solution is decolorized, 10 cc. of the sample is shaken with
it. If rape oil is present, the color will be partially restored. To
prevent the formation of the color by contact with the air have the
vessel full of the mixture.
CHAPTER XII
BEVERAGES
COFFEE
Coffee is often colored with such substances as Scheele’s green, chrome
yellow, iron oxide, Prussian blue, indigo and turmeric. Imitation coffee
beans have been made of wheat flour, bran, rye, chicory and peas.
_Allen’s Preliminary Test._--A good preliminary test for ground coffee
is to sprinkle some of it on the surface of cold water. The oil of true
coffee prevents the particles from being readily soaked, and so they
float for some time. Chicory and most of the other adulterants of coffee
contain no oil, but do contain caramel, which is quickly extracted by
the water producing a zone of brown color about such particles. They
become soaked and quickly sink. The liquid containing pure coffee
diffuses uniformly without coloring the water to any perceptible degree.
Chicory and similar roots give a dark brown, turbid infusion. Roasted
cereals do not impart so distinct a color to water.
COLORING MATTER
Shake the coffee beans in cold water and make the regular qualitative
tests for the inorganic coloring matters--Scheele’s green may be
identified by testing for copper and arsenic; chrome yellow, by testing
for lead chromate; iron oxide may be detected by its characteristic
tests.
Organic coloring matter is best extracted with alcohol. Prussian blue
may be detected by dissolving it from the sediment with hot caustic
alkali, acidifying with hydrochloric acid, treating it with a drop of
ferric chlorid. If present, ferric ferrocyanide, a blue precipitate,
will be formed. Indigo is not discharged by sodium hydroxid, while
Prussian-blue is. It will form a deep blue solution with sulfuric acid.
Test for turmeric as under mustard.
IMITATION COFFEE BEANS
Most imitation coffee, as already stated, is heavier than water. Coffee
contains no starch, so the imitation beans made of cereals may be
detected by testing for starch.
STARCH
_Allen’s Method._--Boil the coffee in 10 parts of water. When perfectly
cold add to it a little sulfuric acid, then a strong solution of
potassium permanganate, drop by drop, with constant shaking, till the
liquid is almost decolorized; strain or decant and add to the solution a
solution of iodin. If 1 per cent or more of starch is present, a blue
coloration will be produced.
CHICORY
_Rimmington’s Test._--Boil a portion of the sample with water which
contains a little sodium carbonate; decant, wash and treat the residue
with a weak solution of bleaching powder for several hours. The solution
will be decolorized. The coffee will be at the bottom as a dark layer
while the chicory will be a light layer above it.
_Albert Smith’s Test._--Boil 10 grams of the sample in 250 cc. of water;
strain and add basic lead acetate in slight excess. A precipitate forms,
and when it has settled the supernatant liquid will be colorless if the
coffee is pure, but more or less colored if chicory is present.
TEA
Tea is adulterated by the substitution of inferior grades for those of
better quality, by the addition of exhausted leaves and foreign leaves,
by the use of coloring matter or “facing” such as Prussian blue, indigo,
or turmeric to color green tea, and sometimes graphite to color black
tea. Foreign astringents (generally catechu) are added to conceal the
presence of exhausted leaves. An imitation tea, “lie tea,” is made of
the stems and dust with mineral matter, and some starch or gum to hold
these together.
FOREIGN LEAVES
Though there are several chemical tests for foreign leaves, none are as
satisfactory as a microscopical examination. Soften the leaves by
soaking in hot water, unroll carefully and examine with a hand lens or
low power of the microscope. Compare with a genuine leaf--the shape,
margin, and venation.
EXHAUSTED TEA LEAVES
Sometimes such leaves may be detected by a physical examination. They
are often more or less unrolled and broken on the edges. But the only
certain way of ascertaining their presence is to determine the soluble
ash which is from 2.5 to 4 per cent in pure tea and usually less than
0.8 per cent in exhausted tea.
LIE TEA
This imitation tea is easily detected by pouring hot water over the
leaves. If they are artificial, they will break down into the fragments
of which they were made.
FACING
Organic coloring matter may be detected by the same method used for
detecting such colors in coffee.
CATECHU
_Hager’s Test._--Boil a little of the tea in water, and add to the
extract an excess of lead monoxid. If the tea is pure the addition of a
solution of silver nitrate produces only a slight grayish precipitate,
but when catechu is present a yellow flocculent precipitate forms.
A FEW OF THE BEST BOOKS ON FOOD ANALYSIS
ALLEN, A. H., Commercial Organic Analysis, 1898. Price, $29.50.
BLYTH, A. W., Foods, their Composition and Analysis, 1903. Price,
$8.40.
HASSALL, A. H., Food, its Adulterations and the Methods for their
Detection, 1874.
LEACH, A. E., Food, Inspection and Analysis, 1905. Price, $7.50.
LEFFMANN, H., and BEAM, W., Select Methods of Food Analysis, 1905.
Price, $2.50.
U. S. Dept. of Agr., Bureau of Chem., Bulletin 13, Parts 1-10, Food
and Food Adulterants, 1887-1902. (Some of these are out of print.)
Bulletin 46, Methods of Analysis of Foods, 1899; Bulletin 65,
Provisional Methods for the Analysis of Foods, 1902.
WILEY, H. W., Foods and their Adulteration, 1907. Price, $4.00.
CHEMICALS
The following are the chemicals used in making all the tests in this
book. Most of these are found in every chemical laboratory.[1]
Acetic acid
Ammonium carbonate
Ammonium chlorid
Ammonium hydroxid
Ammonium sulfid
Amyl alcohol
Aniline
Barium chlorid
Barium peroxide
Boric acid
Bromine
Calcium carbonate
Calcium chlorid
Calcium sulfate
Cane sugar
Carbon bisulfid
Castor oil
Chloroform
Diphenylamine
Ether
Ethyl alcohol
Ferric chlorid
Formalin
Fuchsin
Gelatin
Glycerol
Hydrochloric acid
Iodin
Lead acetate (basic)
Lead oxide
Lime water
Litmus paper
Logwood chips
Mercury (metallic)
Mercury sulfate
Methyl alcohol
Molybdic oxide
Nitric acid (sp. gr. 1.42)
Oxalic acid
Petroleum spirit
Phenolphthalein
Phenylhydrazine hydrochlorid
Phosphoric acid
Potassium bichromate
Potassium carbonate
Potassium chromate
Potassium ferrocyanid
Potassium hydroxid
Potassium iodate
Potassium iodid
Potassium nitrate
Potassium permanganate
Pyrogallic acid
Resorcin
Silver nitrate
Sodium acetate
Sodium acid sulfite
Sodium carbonate
Sodium chlorid
Sodium hydroxid
Sulfur
Sulfuric acid
Tannic acid
Turmeric paper
Zinc (arsenic free)
[1] The more uncommon ones may be obtained from Eimer and Amend, 205-211
Third Avenue, New York.
INDEX OF AUTHORS AND TESTS
PAGE
Allen, A. H., Heavy metals in fruits and fruit products, 37
in meat, 11
in vinegar, 58
Sulfuric Acid (distinguished from Sulfates) in
vinegar, 57
Tartar in vinegar, 59
Amthor, Caramel in fruit and fruit products, 36
Ashby, Free mineral acids in vinegar, 56
Beckmann, Starch in jellies, 38
Bell and Carter, Alum in flour, 16
Boettger, Ergot in rye flour, 18
Bornstein, Saccharin in canned vegetables, 27
Blyth, Alum in bread, 19
Courley and Coremon, Horseflesh in other meats, 14
Ebers, Diseased meat, 14
Frear, Sulfuric acid in vinegar, 57
Geisler, Coal-tar colors in butter, 6
Girard and Dupre, Acid magenta in catsups and tomatoes, 35
Cochineal in catsups and tomatoes, 29
Cochineal in canned vegetables, 29
Gutzeit, Arsenic in canned fruits, 39
Hehner, Formaldehyde in milk, 3
Henzold, Starch in jellies, 6
Hess and Doolittle, Process or renovated butter, test for, 49
Kämmerer, Sulfurous acid in meat, 9
Kleeburg, Wheat in rye flour, 18
Klinger and Bujard, Cochineal carmine in meat, 13
Kraemer, Corn meal in wheat flour, 17
Leach, Caramel in milk, 1
Malic acid in vinegar, 57
Salicylic acid in milk, 4
Salicylic acid in meat, 10
Lythgoe, Coal-tar colors in milk, 2
Marsh, Arsenic in canned fruits, 38
Martin, Coloring matter in butter, 5
Mohler, Benzoic acid in meat, 10
Benzoic acid in fruit and fruit products, 33
Peter, Benzoic acid in canned vegetables, 28
Richards, Mrs., Alum in baking powders, 22
Rimmington, chicory in coffee, 66
Schmidt, Saccharin in canned vegetables, 27
Smith, chicory in coffee, 66
Sostegni and Carpentieri, Coal-tar dyes in canned vegetables, 29
Stoke, Gelatin in milk, 2
Tocher, sesame oil in olive oil, 64
Vanderplanken, Alum in sour bread, 19
Vogel, Substituted flours, 17
Wynter Blyth, alum in flour, 16
Wolff, Tartaric acid (free or combined) in baking powders, 20
INDEX
PAGE
Acid magenta in fruit and fruit products, 35
Agar agar in fruit and fruit products, 37
Alkali in vanilla extract, 45
Allen, A. H., heavy metals in fruit and fruit products, 37
in meat, 11
in vinegar, 58
sulfuric acid in vinegar, 57
tartar in vinegar, 59
test of coffee, 65
Alum in baking powders, 22
in bread, 18
in flour, 16
in pickles, 31
Aluminium salts in cream of tartar, 23
Ammonia in cream of tartar, 23
Ammonium salts in baking powders, 21
Amthor, caramel in fruit and fruit products, 36
Annatto in butter, 5
in milk, 1
Aniline red in meat, 13
Apple juice in jellies made from small fruits, 36
Arsenic in fruit and fruit products, 38
Ashby, free mineral acids in vinegar, 56
Bach, test of olive oil, 62
Baking powders, 20
Adulterations of, 20
Alum, 22
Ammonium salts, 21
Gypsum, 21
Sulfates (calcium, etc.), 21
Tartaric acid (free), 21
Tartaric acid (free or combined), 20
Beckmann, gelatin in jellies, 38
Bell and Carter, alum in flour, 16
Beef stearin in lard, 61
Benzoic acid in meat, 10
in canned vegetables, 27
in fruit and fruit products, 34
Blyth, alum in bread, 19
Boettger, Ergot in rye flour, 18
Borax in fish and oysters, 13
in meats, 9
Boric acid in fish and oysters, 13
in meat, 9
in milk, 4
Bornstein, saccharin in canned vegetables, 27
Bread, 18
Adulterations of, 18
Alum, 18
Copper sulfate, 19
Butter, 5
Adulterations of, 5
Coloring matter, 5
Annatto, 5
Coal-tar colors, 5
Marigold, 6
Saffron, 6
Turmeric, 6
Cottonseed oil, 7
Oleomargarine, 7
Process or renovated butter, 6
Cane sugar in honey, 49
Canned and bottled vegetables, 24
Adulterations of, 24
Alum in pickles, 31
Coal-tar colors, 29
Cochineal, 29
Coloring matter, 29
Copper salts in green pickles, beans, peas, etc., 30
Turmeric in mixed pickles, 30
Examination of can or box, 31
Heavy metals other than copper (see under meats), 11
Preservatives, 25
Benzoic acid, 27
Formaldehyde, 25
Saccharin, 26
Salicylic acid, 26
Sulfurous acid, 26
Soaked vegetables, peas, beans, and corn, 30
Caramel in fruit and fruit products, 36
in milk, 1
in vanilla extract, 47
in vinegar, 58
Catechu in tea, 68
Cayenne pepper in black pepper, 54
in mustard, 53
Cereal products, 16
Chicory in coffee, 66
Citral in lemon extract, 42
Citric acid in lemon extract, 43
Coal-tar colors in butter, 5
in canned vegetables, 29
in fruit and fruit products, 35
in lemon extract, 45
in milk, 2
in vinegar, 58
Cochineal carmine in canned vegetables, 29
in fruit and fruit products, 35
in meat, 13
Coffee, 65
Adulterations of, 65
Chicory, 66
Coloring matter, 65
Imitation coffee beans, 66
Starch, 66
Coloring matters
Acid magenta in fruit and fruit products, 35
Annatto in butter, 5
in milk, 1
Aniline red in meat, 13
Caramel in fruit and fruit products, 36
in milk, 1
in vanilla extract, 47
in vinegar, 58
Copper salts in canned vegetables, 30
Coumarin in vanilla extract, 48
Copper sulfate in bread, 19
in flour, 17
Copper salts in canned vegetables, 30
Cottonseed oil in butter, 7
in lard, 60
in olive oil, 62
stearin in lard, 60
Courley and Coremon, horseflesh in other meats, 14
Cream of tartar, 22
Adulterations of, 22
Aluminium salts, 23
Ammonia, 23
Earthy materials, 23
Tartaric acid (free or combined), 22
Dairy products, 1
Ebers, diseased meat, 14
Eggs, test for freshness, 14
Elaiden test, 62
Exhausted tea leaves in tea, 67
Facing in tea, 68
Fats and Oils, 60
Lard, 60
Adulterations of, 60
Beef stearin, 61
Cottonseed oil, 60
stearin, 60
Olive oil, 61
Adulterations of, 61
Cottonseed oil, 62
Peanut oil, 63
Rape oil, 64
Sesame oil, 64
Fish, preservatives in, 13
Flavoring extracts, 42
Flour, 16
Adulterations of, 16
Alum, 16
Copper sulfate, 17
Substituted flours, 17
Corn meal in wheat flour, 17
Ergot in rye flour, 18
Wheat flour in rye flour, 18
Flour in mustard, 51
Formaldehyde in canned vegetables, 25
in milk, 3
Frear, sulfuric acid in vinegar, 57
Fruit and Fruit Products, 33
Adulterations of, 33
Agar agar, 38
Apple juice in jellies made from small fruits, 36
Arsenic, 38
Coloring matter, 35
Acid magenta, 35
Caramel, 36
Coal-tar dyes, 35
Cochineal, 35
Gelatin in jellies, 37
Heavy metals, 38
Preservatives, 33
Benzoic acid, 34
Saccharin, 34
Salicylic acid, 34
Starch in jellies, jams, and such products, 37
Gelatin in honey, 50
in jellies, 37
in milk, 2
Geisler, coal-tar colors in butter, 6
Ginger cake, stannous chlorid in, 19
Girard and Dupre, acid magenta in fruit and fruit products, 35
cochineal in catsups and tomatoes, 29
in canned vegetables, 29
Glucose in honey, 50
in maple syrup, 50
Gutzeit, arsenic in canned fruits, 39
Gypsum in baking powders, 21
Heavy metals in canned vegetables, 11
in fruit and fruit products, 38
in meat, 11
Hehner, formaldehyde in milk, 3
Henzold, gelatin in jellies, 37
Hess and Doolittle, test for process butter, 6
Honey, 49
Adulterations of, 49
Cane sugar, 49
Commercial glucose, 50
Gelatin, 50
Horseflesh in sausage and mince-meat, 14
Hydrochloric acid in vinegar, 57
test for formaldehyde, 3, 25
Imitation coffee beans, 66
Kämmerer, sulfurous acid in meat, 9
Kleeburg, wheat in rye flour, 18
Klinger and Bujard, cochineal-carmine in meat, 13
Kraemer, corn meal in wheat flour, 17
Lard, 60
Adulterations of, 60
Beef stearin, 61
Cottonseed oil, 60
stearin, 60
Leach, caramel in milk, 1
malic acid in vinegar, 57
salicylic acid in meat, 10
in milk, 4
Lemon extract, 42
Adulterations of, 42
Citral, 42
Coloring matter, 45
Coal-tar dyes, 45
Turmeric, 45
Lemon oil, 42
Methyl alcohol, 43
Oil of citronella, 43
Tartaric or citric acid, 43
Lemon oil in lemon extract, 42
Lie tea in tea, 67
Lythgoe, coal-tar colors in milk, 2
Malic acid in vinegar, 57
Maple syrup, 50
Adulterations of, 50
Glucose, 50
Marigold in butter, 6
Marsh, arsenic in fruit and fruit products, 38
Martin, coloring matter in butter, 5
Martius yellow in mustard, 52
Meats, 8
Adulterations of, 8
Canned, 11
Coloring matter (see under sausages, etc.), 13
Heavy metals, 11
Preservatives (same tests as under smoked and fresh meat), 11
Coloring matter, 13
Aniline red and cochineal-carmine in sausage chopped meat
preparations, and corned meat, 13
Diseased meat, 14
Fresh and smoked, 8
Preservatives, 8
Benzoic acid, 10
Boric acid, 9
Potassium nitrate, 8
Salicylic acid, 10
Sulfurous acid, 9
Fish, salt, dried and oysters, 13
Preservatives, 13
Borax (same as under fresh meat), 13
Boric acid (same as under fresh meat), 13
Horse-flesh in sausage and in mince-meat, 14
Starch in sausage, deviled meat and similar products, 13
Metallic impurities in vinegar, 58
Methyl alcohol in lemon extract, 43
Mineral acids in vinegar, 56
Milk, 1
Adulterations of, 1
Coloring matter, 1
Annatto, 1
Caramel, 1
Coal-tar dyes, 2
Gelatin, 2
Preservatives, 3
Boric acid, 4
Formaldehyde, 3
Salicylic acid, 4
Starch, 2
Mohler, benzoic acid in meat, 10
in fruit and fruit products, 34
Mustard, 51
Adulterations of, 51
Cayenne pepper, 53
Coloring matter, 51
Martius yellow or analogous coal-tar dyes, 52
Turmeric, 52
Flour, 51
Oil of citronella in lemon extract, 43
Oleomargarine in butter, 7
Olive oil, 61
Adulterations of, 61
Cottonseed oil, 62
Peanut oil, 63
Rape oil, 64
Sesame oil, 64
Olive stones in pepper, 53
Oysters, preservatives in, 13
Peanut oil in olive oil, 63
Pepper (common), 53
Adulterations of, 53
Cayenne pepper, 54
Ground olive stones, 53
Peter, benzoic acid in canned vegetables, 28
Pontet, general test of olive oil, 62
Potassium nitrate in meat, 8
Preservatives:
Benzoic acid in canned vegetables, 27
in fruit and fruit products, 34
in meat, 10
Boric acid in fish and oysters, 13
in meat, 9
in milk, 4
Formaldehyde in canned vegetables, 25
in milk, 3
Potassium nitrate in meat, 8
Saccharin in canned vegetables, 26
in fruit and fruit products, 34
Salicylic acid in canned vegetables, 26
in fruit and fruit products, 34
in meat, 10
in milk, 4
Sulfites in canned vegetables, 26
Sulfurous acid in canned vegetables, 26
Process or renovated butter, 6
Rape oil in olive oil, 64
Resins, foreign, in vanilla extract, 46
Richards, Mrs., alum in baking powders, 22
Rimmington, chicory in coffee, 66
Saccharin in canned vegetables, 26
in fruit and fruit products, 34
Saffron in butter, 6
Salicylic acid in canned vegetables, 26
in fruit and fruit products, 34
in meat, 10
in milk, 4
Schmidt, saccharin in canned vegetables, 27
Schmidt, Albert, chicory in coffee, 66
Soaked vegetables, 30
Sostegni and Carpentieri, coal-tar dyes in canned vegetables, 29
Spices in vinegar, 59
Stoke, gelatin in milk, 2
Substituted flours, 17
Corn meal in wheat, 17
General test for, 17
Wheat flour in rye, 18
Sulfates in baking powders, 21
Sulfuric acid in vinegar, 56
Sulfurous acid in meat, 9
Stannous chlorid in ginger cake, 19
Starch in fruit and fruit products, 37
in milk, 2
Tannin in vanilla extracts, 47
Tartar in vinegar, 59
Tartaric acid in baking powders, 20, 21
in cream of tartar, 22
in lemon extract, 43
in wine vinegar, 59
Tea, 67
Adulterations of, 67
Catechu, 68
Exhausted tea leaves, 67
Facing, 68
Foreign leaves, 67
Lie tea, 67
Tocher, sesame oil in olive oil, 64
Turmeric in butter, 6
in lemon extract, 45
in mixed pickles, 30
in mustard, 52
Vanilla extract, 45
Adulterations of, 45
Alkali, 46
Caramel, 47
Coumarin, 48
Foreign resins, 46
Tannin, 46
Vanderplanken, alum in sour bread, 19
Vinegar, 55
Adulterations of, 55
Coloring matter, 58
Caramel, 58
Coal-tar colors in wine vinegar, 58
Glucose, 59
Malic acid, 57
Metallic impurities, 58
Mineral acids (free), 56
Hydrochloric acid, 57
Sulfuric acid, 56
Spices, 59
Tartar in wine vinegar, 59
Tartaric acid (free) in wine vinegar, 59
Vogel, substituted flours, 17
Wynter Blyth, alum in flour, 16
Wolff, tartaric acid free or combined in baking powders, 20
Transcriber’s Notes
This text follows the source document in spelling and hyphenation,
including inconsistencies, except as mentioned below. Inconsistencies in
section heading have been retained as well.
The index entries are not always in alhabetical order; this has not been
changed.
Changes made to the text:
Some missing or wrong punctuation has been corrected silently.
Ratios have been changed to x : y where relevant.
Minor typographical errors corrected:
Page vii: Commerical to Commercial
Page 16: oelomargarine to oleamargarine
Page 49: invert suger to invert sugar
Page 62: ... (about 3 cc. of this ... to ... (about 3 cc.) of this ...
Page 71: seasame to sesame
Page 68: A FEW OF THE BEST BOOKS ON FOOD ANALYSIS has been considered a
separate chapter.
Page 69: the page header CHEMICALS has been used as the chapter heading.
The following words in the indexes have been changed to conform to those
in the text: Bechman to Beckmann; Kammerer to Kämmerer; Klingler to
Klinger; Winter-Blyth and Winter Blyth to Wynter Blyth.
*** End of this LibraryBlog Digital Book "Detection of the Common Food Adulterants" ***
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