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Title: Experiments on the Spoilage of Tomato Ketchup
Author: Bitting, A. W.
Language: English
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*** Start of this LibraryBlog Digital Book "Experiments on the Spoilage of Tomato Ketchup" ***
Issued January 9, 1909.
U. S. DEPARTMENT OF AGRICULTURE,
BUREAU OF CHEMISTRY--BULLETIN No. 119.
H. W. WILEY, Chief of Bureau.
EXPERIMENTS ON THE SPOILAGE
OF TOMATO KETCHUP.
BY
A. W. BITTING,
INSPECTOR, BUREAU OF CHEMISTRY.
[Illustration: Shield of the United States Department of Agriculture]
WASHINGTON:
GOVERNMENT PRINTING OFFICE.
1909.
LETTER OF TRANSMITTAL.
U. S. Department of Agriculture,
Bureau of Chemistry,
_Washington, D. C., July 15, 1908_.
Sir: I have the honor to submit for your approval a report made by
Inspector Bitting of experimental work on the spoilage of tomato
ketchup, the conditions contributing thereto, methods of prevention,
the action of preservatives, and the length of time that the product
will keep under varying conditions of manufacture and temperature, both
before and after opening. Every effort has been made to conduct the
work in a practical way, and the results obtained can not fail to be of
interest and profit both to the manufacturer and consumer. I recommend
that this report be published as Bulletin No. 119 of the Bureau of
Chemistry.
Respectfully, H. W. Wiley,
_Chief_.
Hon. James Wilson,
_Secretary of Agriculture_.
CONTENTS.
Page.
Introduction 7
Process of manufacture 8
Selection and preparation of stock 9
Pulping 9
Cooking and seasoning 10
Evaporation and finishing 11
Bottling 11
Processing 11
Character of products 12
First-class products 12
Inferior products from “trimming stock” 13
Labels 14
Manufacturing experiments without the use of preservatives 15
Outline of experiments 15
Discussion of results 17
Spoilage of ketchup after opening 17
Spoilage of unopened ketchup 20
Spoilage of market brands 20
Sterility of ketchup 21
Experiments with preservatives 22
Sodium benzoate 22
Salt 23
Sugar 23
Spices 24
Water infusions 24
Acetic acid extracts 25
Oil extracts 25
Vinegar and acetic acid 26
Oil 27
Study of Penicillium in ketchup 28
Development 29
Reproduction 29
Growth in ketchup 30
Temperature tests 31
Histological structure of ketchup 33
Microscopical examination of some commercial brands 34
Summary 35
ILLUSTRATIONS.
PLATES.
Page.
PLATE I. Penicillium. Fig. 1.--Conidia, normal growth
and in various stages of germination, some with branching
hyphæ. Fig. 2.--Conidiophore, showing unusually large
development of conidia; from culture in moist chamber 28
II. Cultures from ketchup preserved with sodium
benzoate. Fig. 1.--Conidia and hyphæ from culture in
experimental ketchup containing one-sixteenth of 1 per cent
of sodium benzoate. Fig. 2.--Conidia and hyphæ from culture
in experimental ketchup containing one-tenth of 1 per cent
of sodium benzoate 28
TEXT FIGURES.
Fig. 1. A model receiving platform 8
2. Large receiving room showing the sorting belt 9
3. A section of a kitchen showing the copper cookers 10
4. An example of factory practice 12
5. Another factory interior 14
EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP.
INTRODUCTION.
The tomato, _Lycopersicum esculentum_, is supposed to be native to
South or Central America. The large fruits commonly used grow only
under cultivation, but the variety with small, spherical fruits,
known as _L. cerasiforme_, has been found on the shore of Peru and is
considered by De Candolle[A] as belonging to the same species as _L.
esculentum_. Though grown extensively in Europe, there is nothing to
indicate that it was known there before the discovery of America. The
tomato was introduced into China and Japan at a comparatively recent
date. De Candolle is of the opinion that the tomato was taken to
Europe by the Spaniards from Peru and was later introduced into the
United States by Europeans. Tomatoes were brought to Salem, Mass., by
an Italian painter in 1802,[B] who is said to have had difficulty in
convincing the people that they were edible. They were used in New
Orleans in 1812, though as late as 1835 they were sold by the dozen in
Boston. After 1840 they came into general use in the Eastern States,
but it was later than this before tomatoes were used freely in the
Western States, many persons having the impression that, since they
belonged to the nightshade family, they must be unwholesome. The extent
to which tomatoes are used at the present time shows how completely
this prejudice has been overcome.
[A] Origin of Cultivated Plants, 1890.
[B] Webber, H. J., Yearbook, U. S. Department of Agriculture, 1899.
The name _Lycopersicum_ is from two Greek words, meaning a wolf, and
a peach, the application of these terms not being apparent; the name
of the species, _esculentum_, is from the Latin, meaning eatable.
The common name “tomato” is of South or Central American origin, and
is believed to be the term used in an ancient American dialect to
designate the plant,[C] but its meaning is unknown. The English call
the tomato “love apple,” which in French is “pomme d’amour.”
[C] U. S. Dept. Agr., Exper. Sta. Record, 1899-1900, 11: 250.
The tomato is considered a typical berry, the ovary wall, free from the
calyx, forming the fleshy pericarp, which incloses chambers filled with
a clear matrix containing the seeds. The fruit measures from 1 to 5
inches in diameter, and is red, pink, or yellow when mature.
The plant sports freely, producing many varieties, which differ mainly
in the size, shape, and quality of the fruit. The varieties bearing
small fruits are _L. cerasiforme_ and _L. pyriforme_, each bearing a
two-celled fruit, the former being round, and somewhat larger than
a cherry, and the latter pear-shaped. These small tomatoes are used
ordinarily for preserves and pickles.
The word “ketchup” is adopted in this bulletin as the form which ought
to be given preference. The derivation of the term is not definitely
known. The spelling “catchup” given in some of the leading dictionaries
appears to be based on the erroneous idea that the first syllable
“ketch” is a colloquial form of “catch.” Several authorities derive the
word from the East Indian or Malayan “kitjap,” because “ketchup” was
originally a kind of East Indian pickles. Some give the word a Chinese
origin, while others assert that it comes from the Japanese. A majority
of the manufacturers employ the word “catsup,” a spelling for which
there does not appear to be any warrant.
PROCESS OF MANUFACTURE.
[Illustration: Fig. 1.--A model receiving platform.]
The making of tomato ketchup consists essentially in reducing tomatoes
to pulp, removing the skins, seeds, hard parts, and stems, adding
salt, sugar, condiments, and vinegar to suit the taste, and cooking
to a proper consistency. The methods and practices of the various
manufacturers differ, and the difference between the best and the
poorest procedure corresponds to that between the best and the worst
ketchup. No single factory has all of the best methods at every step
of manufacture. Some perform certain details well and are negligent
in others. In some, large amounts of money are spent on equipment to
improve a particular point considered advantageous by the trade, while
other details essential to the making of a good-keeping ketchup are
disregarded. A statement of the best practice as observed at a number
of factories, together with some facts obtained from experiments, will
be given.
SELECTION AND PREPARATION OF STOCK.
The tomatoes should be home-grown, of a red variety having the minimum
of yellow and purple color, be picked when ripe, and delivered to
the factory promptly without mashing. All tomatoes should pass over
an inspection table, the rotten and otherwise unfit fruit should be
discarded, and the green tomatoes should be returned to crates to
ripen. The stems should be removed when the best color is desired,
and the tomatoes should be thoroughly washed to remove dirt and mold.
Dumping a crate of tomatoes into a hopper of dirty water and playing a
gentle spray of water on part of them merely wets the skin and makes
them appear bright.
[Illustration: Fig. 2.--Large receiving room showing the sorting belt.]
PULPING.
The clean tomatoes should be conveyed to the steaming tanks and
subjected to steam heat until the skins burst and the meat softens.
After a short heating the tomatoes should be run through a “cyclone”
where the skins, seeds, etc., are removed and they are rubbed to a
pulp. To remove very small particles and fiber, the pulp may be run
through a sieving machine at once; or, if ketchup of the smoothest
possible kind is to be made, this procedure should be delayed until
after the cooking. The pulp is collected in a receiving vat, and
only such an amount should be provided in advance as will keep the
kettles full, as it is better to stop the tomatoes before going to
the washer than to have the pulp stand for some hours. In common
practice, however, the pulp is either sent to the cooker at once, or
it is allowed to stand and partially separate. If tall casks are used
for this separation the solids will rise to the top and the clear
watery portion is drawn off at the bottom, or the pulp may be strained
through cloth bags. The object of this separation is to secure greater
concentration of the solids, retain a brighter color, and shorten the
time of cooking.
COOKING AND SEASONING.
[Illustration: Fig. 3.--A section of a kitchen showing the copper
cookers.]
The cooking may be done in copper kettles, as shown in figure 3, though
these are being superseded by enamel tanks containing silver-plated
coils in order to secure the brightest color. By using the latter the
discoloration due to the splashing of the contents against the walls of
the copper vessel is avoided, and economy of space is secured. Whole
or ground spices, or acetic acid or oil extracts of the spices may be
added to the pulp in such proportion as the particular brand demands.
The spices most used are cloves, cinnamon, mace, and cayenne pepper;
but paprika, pepper, mustard, cardamon, coriander, ginger, celery, and
allspice are used by some manufacturers. When whole spices are used,
it is the practice to suspend them in a cloth bag or a wire basket and
to take them out after boiling. They tend to darken the color of the
ketchup, a result considered undesirable by some. The ground spices
are used sparingly, with the exception of cayenne pepper. The acetic
acid extracts of spices are used because they are economical and give
a brighter red color than is obtained with the whole spice. The oil
extracts produce no discoloration, but they are the most expensive and
give an objectionable flavor. Hungarian sweet paprika is now quite
largely used and adds to the color as well as to the flavor. Sugar,
salt, and vinegar are added in such proportion as may be desired, and
in some brands onions and garlic are used.
EVAPORATION AND FINISHING.
The pulp is evaporated rapidly to such consistency as the grade and
price will warrant, the reduction in volume being from 40 to 60 per
cent. This is accomplished in about forty-five minutes. The cooking is
not continued longer than is necessary, as each minute added to the
cooking darkens the finished product.
If the pulp has been run through the sieving machine before cooking,
the batch may be drawn off into the receiving tank for bottling. If the
finishing be done after cooking, the pulp is run into a receiving vat,
finished as quickly as possible, and drawn into the tank for bottling.
The ketchup may be kept at a high temperature--200° to 206° F.--in the
receiving tank by means of a small steam coil, or it may be drawn to
the bottling machine through a steam-jacketed tube. Finishing after
cooking yields a slightly smoother ketchup than sieving before cooking;
but it necessitates handling, reduces the temperature, and increases
the chances of infection.
BOTTLING.
The bottles should be thoroughly cleaned as ketchup will not keep if
placed in bottles which have been merely rinsed to remove the straw; if
the ketchup is not to be given an after process the containers should
be sterilized. In the experimental work cork stoppers gave the best
results and these should be sterilized in a paraffin bath at 250° F.
PROCESSING.
An after treatment or process is given to bottled goods either in a
water or steam bath, the important point being that the center of the
bottle be raised to the desired degree of heat. If the ketchup is thin
this can be effected quickly, but if it is thick and heavy the heat
penetrates the ketchup with surprising slowness. In a thin ketchup
the temperature may be raised from 140° to 190° F. in eighteen minutes
or less when the surrounding heat is 195° F; but in a heavy ketchup it
may take an hour or more to accomplish the same result. It is therefore
very important that the ketchup be processed immediately after it is
corked, before it has time to cool. The rate at which the heating is
effected for different goods can be determined by sealing a thermometer
in the cork and recording the readings.
[Illustration: Fig. 4.--An example of factory practice showing the
top row of tanks from which pulp passes by gravity into the cookers,
then into the receiver, sieving machine, and final tub ready for the
bottling machine or jug filler.]
CHARACTER OF PRODUCTS.
FIRST-CLASS PRODUCTS.
The factory at which the experiments were conducted has sanitary
buildings and surroundings, the floors are of concrete for flushing,
and the pipes used in conducting the pulp to the kitchens are
porcelain-lined to prevent discoloration from the iron and to insure
cleanliness. The tubes which carry the ketchup from the kettles to the
receiving tank, finishing machine, and bottler are silver-plated. Not
all of these measures are necessary to make a good ketchup, but they
show the care exercised in making an article of good appearance and of
the finest quality.
The conditions under which ketchup is made and the care with which the
work is done at some of the better factories is equal to that used in
the manufacture of any food product. Whole selected fruit is used,
cleanliness is maintained at every point, the best grades of spices,
vinegar, granulated sugar, and salt are added for flavoring, and the
bottles are carefully washed. The ketchup put up under such conditions
will have a bright natural color, will remain good as long as the
container is unbroken, and will continue in that condition for some
time after opening if kept at a fairly cool temperature.
INFERIOR PRODUCTS FROM “TRIMMING STOCK.”
In contrast with the strictly high-grade product is the great bulk
of the ketchup found on the market. The material is not whole ripe
tomatoes, but consists of the waste of the canning factory, commonly
designated as “trimming stock,” including the green, moldy, broken,
rotten, and generally unusable tomatoes, the skins, cores, and stems
from the peeling tables, and the surplus juice from the filling
machines, all of which may be allowed to stand during the day and be
run through the cyclone in the evening. At the end of the season, the
frosted and half-ripe fruits may be used. Part of this material can
not be considered “sound fruit” as contemplated by the food and drugs
act. The pulp is put up in barrels, preserved, and allowed to stand,
possibly in the sun, until a sufficient quantity has accumulated for
shipment. Old ketchup barrels may be used and be none too clean. As a
result, it is not uncommon to see an inch or more of pulp in the bottom
of a car at the end of shipment, caused by the blowing out of the
barrel heads from fermentation. The sanitary condition of the factory
may be poor, the handling of the goods be unclean, the spices be the
refuse from the spice houses, the sugar be of the cheapest grade, and
the bottles be only rinsed or be used without even that precaution.
The ketchup is a concoction so heavily spiced with hot spices that the
tomato flavor is lost and might as well be anything else. The color is
normally dirty brown.
Between these two extremes are all grades, those for which whole
tomatoes, unsorted, are used, those for which trimming stock is worked
up promptly during the canning season, and those made from stock of
unknown history. Some manufacturers work under good and some under poor
sanitary conditions. There can be no doubt that with proper selection
and precaution much of the by-product of the canning factory and large
quantities of tomatoes which are unsuitable for canning might be used
to advantage in the manufacture of ketchup; but it requires a nicety
of practice not generally found at this time. The practice sometimes
followed of making some ketchup from whole stock and a large quantity
from refuse and using the former for advertising purposes, only serves
to emphasize the fact that the goods belong to two distinct classes.
One of the uses for a very considerable amount of pulp from refuse
stock is the making of sauce for baked beans and other canned goods
where the true character can not be observed by the consumer.
[Illustration: Fig. 5.--Another factory interior, showing large pulp
tanks in the rear, cooking tanks on the right, and process tanks in
front containing thousands of bottles of ketchup.]
During the season tomatoes come in at times in larger quantities than
can be made into ketchup promptly. The surplus must be worked up into
pulp for storage and may be stored in barrels or in tin cans. The pulp
stored in barrels will not have as good a color as that put into cans,
and the ketchup made from either will not be as bright as that made
from whole, fresh stock. The pulp put up in barrels is more liable
to spoilage than that put up in cans. The difference in the cost of
storage by the two methods is not very great, and some large concerns
are using the can exclusively instead of the barrel.
LABELS.
The labels on the ketchup bottles have been improved somewhat in the
last year as regards exactness in describing the contents. Formerly,
according to the labels, much of the ketchup was made from whole
ripe tomatoes. The question was, What became of the enormous amount
of ketchup which it was known had been made from “trimmings?” On this
year’s ketchup the labels make fewer claims, generally merely stating
that it is “tomato ketchup,” which is true whether made from whole
tomatoes or refuse. The brand is in most cases the guaranty for good
quality. It is not safe to judge the quality by the price, for, though
usually good quality can not be expected unless the higher price is
paid, some of the high-priced ketchup when placed under the microscope
has proven to be a very inferior product.
The wide labels on the neck of the bottle are objectionable. Some of
these are 2 inches in height, and serve to cover the discolored and
spoiled ketchup. As spoilage begins usually in the neck of the bottle,
it is difficult to see it when the neck is wrapped with a label, and
thus it might easily be overlooked until the main body of the ketchup
is affected. The bottles which have the widest labels around the neck
are usually the ones provided with one or two large labels on the lower
part of the bottle, though some bottles have no other label but the one
around the neck. As a rule, however, these are narrow, close to the
stopper, and unobjectionable.
In buying ketchup for experimental purposes it was difficult and
sometimes impossible to learn its age, as often the grocer does not
know it, and at other times he will not tell. It appeared, however,
that often the ketchup had been on the grocer’s shelf or in the
warehouse from one to four years.
MANUFACTURING EXPERIMENTS WITHOUT THE USE OF PRESERVATIVES.
OUTLINE OF THE EXPERIMENTS.
During September, 1907, ketchup was made in experimental batches to
determine whether it could be manufactured on a commercial scale
without the use of preservatives. These experiments were made to
determine (1) the keeping quality before opening the container and (2)
the length of time the product will keep without spoilage after the
bottle is opened.
The ketchup was made in a factory in which the conditions of
manufacture and all the surroundings were sanitary; whole, ripe
tomatoes, the same as used in the regular grade of canned goods,
were used and the formula and process were for a mild ketchup giving
the maximum of tomato flavor. Each batch consisted of 50 gallons of
finished goods, from which 1 gross of pint bottles was retained for
observation.
The term “regular ketchup” as used in these experiments means the
pulp of fully ripe tomatoes, to which was added granulated sugar,
80-grain, distilled vinegar, table salt, onions, garlic, whole
cinnamon, cloves, mace, and ground cayenne pepper. The pulp was cooked
in a steam-jacketed copper kettle for forty minutes and reduced
about 50 per cent. The finishing was done after cooking. The regular
bottles are pint sizes, washed in hot water, rinsed, and then heated
to a temperature of 190° F. for thirty minutes or more. The sterile
bottles referred to in the experiments were placed in a steam chamber
for twenty minutes at 230° F. The corks were sterilized by a bath in
paraffin at about 270° F. All of the work was accomplished quickly to
insure a smooth, even product with a bright, clean color. Acetic acid
extracts and oil extracts of spices were used in such quantities as
would give the same amount of spicing as when the whole spices were
employed.
In all of the following experiments the ketchups discussed were made in
September, 1907, and the last examination reported was made ten months
later, in July, 1908:
_Experiment No. 1._--Regular ketchup was made, but it was reheated
after finishing and bottled in sterile bottles at a temperature of
205° F. No spoilage has occurred at the end of ten months.
_Experiment No. 2._--Regular ketchup was made, and it was bottled
immediately after finishing in regular bottles at a temperature of
165° F. An after process was given at 190° F. for twenty minutes.
No spoilage has occurred after ten months.
_Experiment No. 3._--Regular ketchup was made, and was bottled in
regular bottles at 165° F., and given a subsequent process at 190°
F. for forty minutes. No spoilage has occurred.
_Experiment No. 4._--Regular ketchup was made, was bottled in
regular bottles at a temperature of 165° F., and given an after
process at 212° F. for twenty minutes. No spoilage has occurred.
_Experiment No. 5._--Regular ketchup was made, the same being
put up in regular bottles at a temperature of 165° F. and given
an after process at 212° F. for forty minutes. No spoilage has
occurred.
_Experiment No. 6._--Ketchup was made in which the acetic acid
extracts took the place of whole spices, and the bottling was done
at a temperature of 165° F., no after treatment being given. No
spoilage has occurred.
_Experiment No. 7._--Ketchup was made in which acetic acid
extracts were used, and the bottling was done at a temperature of
165° F. in sterile bottles. No after treatment was given and no
spoilage has occurred.
_Experiment No. 8._--Ketchup was made in which the oil extracts
were used instead of regular spices. The bottling was done in
regular bottles at a temperature of 165° F., no after treatment
being given. No spoilage has occurred.
_Experiment No. 9._--Ketchup was made in which oil extracts were
used instead of whole spices. The bottling was done at 165° F. in
sterile bottles, no after treatment being given. No spoilage has
occurred.
_Experiment No. 10._--Regular ketchup was made, but the pulp
was run through the sieving or finishing machine before instead
of after cooking, the object being to determine the effect upon
the character of the goods rather than upon the spoilage. This
practice could be followed to advantage in making all except the
very finest goods, and would give the same condition for bottling
as in experiment No. 1.
_Experiment No. 11._--Pulp was made in the usual manner and run
into barrels while just below the boiling point. The barrels
had been thoroughly washed and then steamed for twenty minutes.
As soon as the pulp had cooled slightly the bung was driven in
tightly and the barrel was rolled into storage. At the end of
sixty days the barrels were opened and the pulp was found to be in
good condition.
_Experiment No. 12._--Regular ketchup was drawn into 5-gallon jugs
which had been sterilized in the same manner as the bottles. These
were kept for sixty days and no spoilage occurred.
DISCUSSION OF RESULTS.
Twelve hundred and ninety-six bottles were shipped from Terre Haute
to Lafayette, Ind., and some were reshipped in order to duplicate
the conditions in trade. Some were kept in a warm temperature and in
strong light, others in a comparatively cool place and in the original
shipping cases, in order to duplicate the conditions in the warehouse
and grocery store. There has been no spoilage after ten months other
than that resulting from four or five cork leaks and neck cracks. These
experiments have shown conclusively that ketchup can be put up on a
commercial scale and delivered to the consumer in perfect condition
without the use of a preservative.
It was demonstrated by the first experiment that the goods could be
bottled at a high temperature without difficulty, and that subsequent
treatment was unnecessary. The after treatment at 190° was tried
because it had been found in small experiments that, in giving a higher
temperature, the internal pressure would cause more or less breakage of
bottles or loosening of corks. After treatment is practiced by some who
also use a small quantity of preservative as a further precaution. This
treatment is continued from two to three hours at the temperature of
high pasteurization.
The process at 212° was given with little breakage, as the bottles
used were of good quality. At and above this temperature the breakage
may be reduced by either raising the temperature of the ketchup before
bottling or applying pressure upon the outside while giving the process.
Neither the acetic acid nor the oil extracts showed any advantage over
whole spices in their preservative effects, as all kept. The color was
slightly improved, but the flavor was impaired, particularly when the
oil extracts were used.
SPOILAGE OF KETCHUP AFTER OPENING.
The question of how long the ketchup should keep after opening the
container in order to satisfy the ordinary requirements of consumption
was also studied. A local restaurant, serving about two hundred meals
and using from one-half to a gallon of ketchup daily, was supplied with
the same kind of ketchup used in the experiments, as were also some
families. Instructions were given to use the ketchup as they would
ordinarily, with the result that none reported any loss from spoilage.
To determine how long the ketchup would keep after opening, 8 bottles
from each of the first 9 experiments were kept in the kitchen at
a temperature of about 72° F., 5 were kept in an incubator at a
temperature of 95° F., 5 were kept in the laboratory at a temperature
of about 67° F., and 4 were kept in an inclosed porch where the
temperature ranged from 30° to 60° F. This made a total of 198 bottles.
No precautions, other than those of ordinary cleanliness, were taken
in opening the bottles, as it was desired to determine the keeping
properties under conditions of general usage. The first set of bottles
was opened November 5, immediately on being received at the laboratory,
all of the ketchup having been kept at the factory until the experiment
begun in September was completed. The bottles were covered loosely with
a metal cap and observed daily, a record being kept of the date and
character of spoilage.
The results showed that the differences in the time and temperature
of processing had little, if any, effect in checking the spoilage;
neither did the use of acetic acid or oil extracts. The most important
precaution in checking the spoilage after opening seems to be to keep
the ketchup cool. This is shown by the average number of days which
elapsed before spoilage occurred in the sets kept under different
temperature conditions. For those kept in the kitchen the average
number of days was six, the minimum three, and the maximum eleven.
Those in the incubator kept for an average of five days, with a minimum
of two days, and a maximum of eight. Those in the laboratory had an
average of eight days, the minimum being four days and the maximum
twenty-two. Those kept in the porch lasted on an average twenty-seven
days, a minimum of twelve days, and a maximum of fifty-eight.
These figures show the definite relation of temperature to spoilage
under the conditions of ordinary use. In making the observations, the
metal cap was removed each day, but no ketchup was poured off. The
spoilage in all cases was due to mold, and usually this formed in the
neck of the bottle where the ketchup had splashed, or at the junction
of the ketchup with the bottle. The spoilage was recorded as soon as
the slightest growth appeared. In actual use if the neck were wiped
out when the ketchup had been used and a growth of mold removed on its
first appearance with some of the proximate ketchup the time before
spoilage occurred could be prolonged. In these experiments the attempt
was made to determine how soon growth appeared under the various
conditions of temperature named.
The unopened bottles of ketchup were kept in a basement room, the
temperature of which is fairly constant, being about 70° F. This is
approximately the condition in a grocery where the ketchup is kept on
the shelves. Another set of samples from the run of September, 1907,
was opened February 11, 1908, to determine if storing in a warm room
before opening had any effect on the length of time preceding spoilage.
Four bottles were taken from each of the first 9 experiments to make
up each of three sets, one of which was kept in the kitchen, one in
the incubator, and one in the porch, making a total of 108 bottles. The
average number of days for those kept in the incubator was four, the
minimum two, and the maximum six. The average number of days before
spoilage in the kitchen was five, the minimum being three and the
maximum nine. Those kept in the porch gave an average of twenty-three
days, the minimum number being eighteen days and the maximum
seventy-three days. Thus it is seen that the ketchup lasted nearly five
times as long at a temperature of 30° to 60° F. as it did at 72°; and
also that when ketchup is kept in a warm place before opening, spoilage
occurs somewhat sooner, the average for the fresh samples opened under
the same conditions being one day more with the incubator and kitchen
samples and four days more with the porch samples.
A third set of bottles of the ketchup was opened on June 6, 1908, or
two hundred and sixty-five days after manufacture. They had been kept
in a basement at a temperature of about 70° F.
One set was placed in the incubator at a temperature of 95° F., one
set in the kitchen at about 82° F., and one set in the refrigerator
at 46° F. The weather was warm and the conditions favorable to the
spoilage of fresh foods. The minimum time for spoilage in the incubator
was two days, the maximum time four days, and the average time three
and two-tenths days. The minimum time in the kitchen was two days,
the maximum time six days, and the average time four and four-tenths
days. The minimum time in the refrigerator was nine days, the maximum
time nineteen days, and the average time thirteen and sixty-six
one-hundredths days.
These data are grouped in the following table for easier comparison:
_Time of spoilage of ketchup at different temperatures after opening._
OPENED ON NOVEMBER 5, 1907, IMMEDIATELY UPON RECEIPT FROM FACTORY;
MAXIMUM AGE, FIVE WEEKS.
-----------------------------------------------------------------
Place of storage. | Temperature. | Lapse of time before spoilage.
| |-------------------------------
| | Average. | Minimum. | Maximum.
------------------| |----------+----------+---------
| _° F._ | _Days._ | _Days._ | _Days._
Incubator | 95 | 5 | 2 | 8
Kitchen | 72 | 6 | 3 | 11
Laboratory | 67 | 8 | 4 | 22
Porch | 30-60 | 27 | 12 | 58
-----------------------------------------------------------------
KEPT AT 70° F. FOR ONE HUNDRED AND FIFTY DAYS BEFORE OPENING ON
FEBRUARY 11.
-----------------------------------------------------------------
Incubator | 95 | 4 | 2 | 6
Kitchen | 72 | 5 | 3 | 9
Porch | 30-60 | 23 | 18 | 73
-----------------------------------------------------------------
KEPT AT 70° F. FOR TWO HUNDRED AND SIXTY-FIVE DAYS BEFORE OPENING ON
JUNE 6.
-----------------------------------------------------------------
Incubator | 95 | 3.2 | 2 | 4
Kitchen | 82 | 4.4 | 2 | 6
Refrigerator | 46 | 13.66 | 9 | 19
-----------------------------------------------------------------
SPOILAGE OF UNOPENED KETCHUP.
Another test was made to determine whether the ketchup would spoil
when kept in a warm place, but not opened. Three bottles from each
experimental batch were placed in the incubator November 7, 1907, and
were kept there until December 23, 1907--forty-six days--and in that
time there was no sign of spoilage. They were then opened and kept in
the laboratory; the average number of days before spoilage occurred is
indicated in the following table:
_Average number of days before spoilage of ketchup after opening (kept
46 days at 95° before opening)._
---------------------------------------
Experiment No. | Days before spoilage.
---------------+-----------------------
1 | 2⅔
2 | 4⅔
3 | 3⅓
4 | 5
5 | 5⅓
6 | 4⅓
7 | 4⅓
8 | 4⅓
9 | 3⅔
---------------------------------------
It will be observed that these samples spoiled in about the same length
of time as the bottles opened in February and tested in the incubator,
so that similar results were obtained by keeping unopened ketchup one
and one-half months at 95° F. and keeping it five months at 70° F. From
the results of the experiments it is evident that the ingredients of
the ketchup in the proportions used are not antiseptic, and it is also
apparent from the number of organisms found and the rapidity of their
multiplication that ketchup is a good, nutritive medium. Yeasts and
molds are the predominating organisms, and, as the ketchup is acid and
also contains sugar, and these organisms are found on tomatoes in the
field, their predominance in the ketchup is explained.
SPOILAGE OF MARKET BRANDS.
To determine the keeping properties of the ketchup on the market,
various brands were obtained from the grocery stores. In the
majority of cases nothing was known of the ingredients or methods of
manufacture, except what appeared on the labels. No date of manufacture
was given, and in some cases the dealers did not know the age of the
product.
There were 104 bottles of ketchup opened to find out how long they
would remain in good condition. These were kept in the laboratory,
though the temperature was higher than that at which ketchup should be
held. Of the 104 bottles there were 66 without preservative, according
to the labels, 46 of which spoiled. Of the 20 which did not spoil, 2
formed crystals of benzoic acid on the covers of glass dishes during
evaporation. Of the 39 which, according to the labels, contained sodium
benzoate, 15 spoiled. The bottles of unspoiled ketchup after remaining
in the laboratory for about a month were placed in the incubator at
95° F. for three weeks, and were then taken out, and have been left in
the laboratory since. The metal cap had been taken off frequently for
observation, and the ketchup exposed, but the treatment did not cause
them to spoil.
The average number of days after which spoilage occurred for the 46
bottles without preservative was about fifteen, the minimum number
being four days, the maximum number ninety-four days. The average
number of days preceding spoilage in the case of 15 bottles with
preservative was twenty-four days, the minimum number being three and
the maximum sixty days. The majority of these had 0.1 per cent of
sodium benzoate present; the others had a smaller amount, according
to the manufacturer’s label. These data are not at all conclusive and
further work on material of known history will be necessary.
STERILITY OF KETCHUP.
To determine the sterility of ketchup, cultures were made from 77 of
the bottles. The method used was to wipe the bottles and cork stoppers
with a damp towel and then remove the cork. The cork puller which
was used grasps the neck of the bottle in such a way as to cover the
opening and remove the cork without the inrush of air that occurs when
the ordinary corkscrew is used. A flame was then passed over the mouth
of the bottle, after which the upper layer of ketchup was poured out,
so as to discard any material which might have been contaminated in
handling. Tomato gelatin was used as a medium and cultures were made in
petri dishes.
There were 17 plates on which no organisms developed, indicating
that the ketchup was sterile. Of the 60 plates having organisms, 54
had molds, 22 of these having molds alone; 21 plates had yeast-like
organisms, 3 plates having these only; 29 plates had bacteria, 4 having
bacteria alone. Sometimes a plate would have only one form of organism,
but more often there was a mixture present. Of 15 plates having only
one form of organism, 3 had yeast alone, 2 bacteria alone, and 10 had
mold alone. Of the 77 bottles of ketchup from which the inoculations
were made, 41 were without and 36 with preservative, and of the 17
sterile ketchups, 8 contained sodium benzoate and 9 were without
preservative.
A considerable part of the experimental ketchup proved not to be
sterile. The organisms present were of the class which require oxygen
for their growth and therefore they had only been arrested in their
activity. No growth could take place so long as the air was excluded
and therefore no spoilage could occur. When the cork was drawn, the
organisms could grow and cause spoilage, and this is a much more
potent factor than the entrance of germs from without. Bottling and
sealing the ketchup quickly while hot so completely excludes the air
that only a few colonies of yeast or mold may be found on subsequent
microscopical examination. Filling at a low temperature and corking
while cool allows sufficient air to remain incorporated in the ketchup
and neck of the bottle to permit a considerable growth of the organisms
and a product derived from good stock may thus acquire the appearance
of ketchup derived from partially decayed material. A ketchup in which
bubbles of air are incorporated in filling may show a growth of mold
at each bubble throughout the mass. The foregoing statements apply to
ketchup containing sodium benzoate as well as to the non-preservative
goods of the character used in these experiments.
EXPERIMENTS WITH PRESERVATIVES.
SODIUM BENZOATE.
The preservative in general use in ketchup is sodium benzoate.
Salicylic acid is used, but only to a limited extent. The amount
of sodium benzoate used, according to the labels, varies from
one-sixteenth to one-tenth of 1 per cent; but on some labels the amount
is not stated. Experiments were made to determine the amount necessary
to check the spoilage of ketchup.
Two organisms, a mold and a yeast, were selected on which to make the
tests. The mold was the ordinary blue mold, Penicillium, which was
present in many of the brands of ketchup and is found commonly on acid
foods. It was selected on account of its prevalence and resistive
power. The yeast was obtained from ketchup and was also a vigorous
grower, forming a thick, wrinkled film on various media. Any effect on
the growth of the yeast could be seen readily in its manner of forming
the film.
Portions of tomato gelatin to which 0.1, 0.5, 1, and 2 per cent,
respectively, of sodium benzoate were added, were first inoculated with
the mold. There was no development in those containing 1 and 2 per
cent; a retarded development resulted in that containing 0.5 per cent,
and the growth when 0.1 per cent was used was nearly normal, showing
very little difference from that in the gelatin without sodium benzoate.
Ketchup was next tried as a medium, but the amount of benzoate was
reduced to one-sixteenth, one-twelfth, and one-tenth of 1 per cent,
as it was thought that some of the other constituents of the ketchup
were antiseptic to a slight degree. The growth in the ketchup was
irregular, though the benzoate checked development in all. Equal
amounts of benzoate were used in tomato bouillon, with practically the
same results as in the ketchup. The development was checked in all,
and in some plates one-sixteenth of 1 per cent seemed to be fully as
efficacious as one-tenth of 1 per cent. When the mold was examined
under the microscope, the filaments were found to be much swollen and
distorted in shape, and filled with a coarsely granular protoplasm,
containing much fat, as indicated by the blackening with osmic acid.
The culture containing the mold which gave the least development seemed
to show the least distortion and swelling of the filaments.
The results indicated that in using sodium benzoate as a preservative
there is uncertainty as to results, even when using the maximum amount
allowed--one-tenth of 1 per cent. They also indicated that this
preservative had an injurious effect on the living matter of the mold.
(See Pl. II; compare with normal growth, Pl. I.)
SALT.
The effect of salt in checking development was tested by using tomato
bouillon as a medium and adding 5, 10, 15, 20, 25, and 30 grams of
salt, respectively, to 100 cc. These were inoculated with the mold. The
5-gram solution seemed to have no effect on development. When 10 grams
were used growth appeared as soon as in the bouillon without salt, but
was not so extensive. In the 15-gram solution growth was retarded four
days, and most of that which did develop remained submerged, the mold
growing normally on the surface. With 20 grams the growth was five
days slower than the normal in starting, and after that there was only
a slight development. In the 25-gram solution, the growth started at
the same time as when 20 grams were employed, but remained stationary,
while with the 30-gram solution, no development occurred.
The yeast was checked slightly by 5 grams, and very materially by the
10-gram solution, as it required two days for a thin, delicate film
to form, whereas in ordinary solutions a rather thick film is formed
within twenty-four hours or even in less time. There was no development
in the 15-gram solution.
SUGAR.
The effect of sugar was tested on both the mold and the yeast by adding
it to tomato bouillon. It was supposed that a low percentage of sugar
like the salt would plasmolyze the cells, and in this way check growth,
but it seemed to have no effect until the amount was increased to 25
grams per 100 cc of bouillon. In this solution growth appeared as soon
as with the weaker solutions, but there was a smaller amount. In the
25 to 40 gram solutions there was less development as the amount of
sugar increased. In the 70 and 75 gram solutions growth was delayed one
day in its appearance. In the 80, 85, and 90 gram solutions growth was
delayed two days, the colonies growing submerged at first, but after
a time forming on the surface. The mycelium remained very thin, but
a thick layer of spores formed. From this point on the amounts were
increased by 10 grams up to 200. The development became slower and less
successively until 170 grams were added. In this case a small colony
appeared on the surface in seven days, but seemed to grow less after
that. The solutions were held, and in time crystals separated from the
thick sirups. After two months dry-looking colonies developed along the
edges, forming a ring, and some formed on the surface, these occurring
also in the flasks containing 170, 180, 190, and 200 grams of sugar per
100 cc. The colonies were a dull greenish drab in spots, the remainder
being white.
For the yeast the 80-gram solution of sugar was the strongest in which
any development took place.
SPICES.
Experiments to determine the value of the spices as antiseptics were
made, using water infusions, acetic-acid extracts, and oil extracts.
WATER INFUSIONS.
In making the water infusions 20 grams of the whole spices, with 200
cc of water, were boiled for forty-five minutes. This is approximately
the length of time that the spices are cooked in the ketchup in the
factory. The liquid was then filtered and from 0.1 to 5 cc of the
filtrate was used in 10 cc of tomato bouillon. The same organisms were
used as in the former experiments.
The tests showed that cinnamon and cloves were the strongest
antiseptically. These checked growth when used in small amounts, but
it required 3 cc of the cinnamon and 1 cc of the cloves to inhibit the
growth of the mold. Mustard, paprika, and cayenne pepper checked growth
also, but 5 cc, the highest strength used, did not inhibit growth. The
ginger, mace, and black pepper had no apparent effect in the quantities
used.
The effect of the spices on the development of the yeast was somewhat
different from their effect on Penicillium. The cinnamon showed the
strongest action, 3 cc being effective, whereas 5 cc of the cloves was
required. The cayenne pepper came next in effectiveness, and after that
the black pepper. The ginger, mace, and mustard solutions had no effect
in the strengths used.
The remainder of the spice infusions were kept in glass-stoppered
bottles in the laboratory, and in a few weeks’ time there was a coating
of mold formed over the surface of the mace, the mustard, and the
black and cayenne peppers. The paprika had small, stunted colonies
dotting the surface.
At the time that these experiments were made a quantity of the ground
spices were placed in large petri dishes and water was added to make a
heavy paste. One set of these was inoculated with the mold, and another
set with the yeast, and all were kept in a warm place. No development
of either organism appeared on the cinnamon, cloves, or mustard; on the
others a growth first showed in three days. On a normal medium growth
appears in twenty-four hours. On the mace, paprika, and cayenne pepper
the Penicillium and yeast with which the pastes were inoculated were
overgrown in a few days with black mold (_Rhizopus nigricans_).
ACETIC-ACID EXTRACTS.
In the manufacture of ketchup acetic-acid extracts of the spices
are sometimes used instead of the whole spices, on account of their
supposed antiseptic properties as well as their greater strength and
convenience in handling. One minim of the standard acetic-acid extracts
is equal in strength to 1 grain of the whole spices. The acid extracts
obtained included allspice, celery, cloves, coriander, garlic, and
black pepper.
In the tests 0.1, 0.2, 0.3, 0.4, 0.5, and 1 cc, respectively, of the
extract was added to 10 cc of tomato bouillon. One set was inoculated
with the mold and another set with the yeast. In the case of the mold,
no growth occurred with the allspice and cloves; the celery checked
the growth materially, there being no indication of mold until the
sixth day. Normally a fairly strong growth occurs in twenty-four hours.
In the solution containing 0.3 cc there was only one small colony in
thirteen days, and no further development. In the solution containing
the coriander, the growth in the 0.5 cc solution did not appear for
three days, the 1 cc solution showing no growth. The garlic had
practically the same effect as the coriander, while the black pepper
was stronger, no growth appearing in the solution containing 0.5 cc.
The yeast was slightly stronger in resisting the effect of the
extracts. No growth appeared with the allspice and cloves; 0.5 cc
of the celery and 1 cc of the coriander were required to inhibit
growth, and the garlic and black pepper gave similar results, a weak
development occurring in the solutions containing 1 cc.
OIL EXTRACTS.
Oil extracts of the spices were tested in the same manner as the water
infusions and the acetic-acid extracts. The oils were so strong that
in order to handle them easily they were mixed with equal volumes of
alcohol, except that the mace, which was in the form of a paste,
was mixed with two-thirds its volume of alcohol. To 10 cc of tomato
bouillon were added 0.1, 0.2, 0.3, 0.4, and 0.5 cc, respectively, of
the oils of cinnamon, cloves, mace, mustard, and black pepper.
In the case of the mold, there was no development in the solutions
containing cinnamon, cloves, and mustard; in those containing mace
and black pepper the development was slower than the normal, that in
the black pepper being more pronounced. On the yeast the effect was
similar, no development occurring in the cinnamon, cloves, and mustard,
and a retarded development taking place in the mace and black pepper,
that in the black pepper being the more pronounced.
The experiments show that some of the spices, notably allspice,
cinnamon, and cloves have decided antiseptic value, but that the
peppers are not as valuable as is generally supposed.
The oil extracts have been advocated for use in ketchup instead of the
whole spices, but in quantities which would be useful antiseptically
their use would be objectionable, for when present in approximately
the same proportions as are the whole-spice infusions, the flavor
is too strong and masks the more delicate flavor of the tomato. The
acetic-acid extracts are more effective than are the water infusions,
and they are not objectionable in the ketchup.
VINEGAR AND ACETIC ACID.
An experiment was made to determine the antiseptic value of vinegar and
acetic acid. Commercial 50-grain distilled vinegar was used. It was
found that when 30 per cent of this vinegar was added to the tomato
bouillon the development of mold was checked and the extent to which
it was checked increased with the increased amounts of vinegar. The
development in the solution containing 30 per cent of the vinegar
was two days later than the normal in starting, while the solution
containing 100 per cent was eleven days delayed and showed but little
growth.
An 80 per cent solution of glacial acetic acid was used. One-half of
1 per cent added to the tomato bouillon checked growth to the same
extent as 30 per cent of vinegar, and no development occurred when the
quantity was increased to 2 per cent.
Experiments were then made in which vinegar was added to the ketchup
in proportions varying from 1 part in 32 to 1 part in 8, with the
result of greatly delaying the appearance of the mold as the proportion
increased. With the increase in vinegar it was necessary to add sugar
and slightly more spices to overcome the pungency of the acid and thus
insure good flavor. The addition of the vinegar to the pulp had the
effect of arresting the action of the oxidase and thus the bright color
was maintained.
The usual custom in factory practice is to add the vinegar near the
close of the cooking process otherwise a considerable portion of the
acid will be driven off. This practice was followed in the experimental
work, but it has since been found that continued heating in the
presence of the acid has some effect upon sterilization, and therefore
the increased amount of vinegar is effective not only because of the
additional acid present, but also because the heating in the after
process is thereby rendered more efficacious.
This line of experiments gives promise of practical results in
producing a ketchup which will not only keep while in the bottle, but
will also keep longer after it is opened. Each manufacturer must work
out the quantities that could be used with his formula and still retain
the character of his goods.
OIL.
In ketchup manufacturing it is customary, if an agitator is not used,
to put a small amount of fat in the kettle to check the ebullition
during the reduction of the pulp. The amount used in this manner is not
sufficient, however, to be apparent in the ketchup. Brannt[D] states
that in some factories, where the trimmings are allowed to accumulate
for the season, they are given liberal doses of oils and condiments
when cooked, in order to disguise their defects, so that the product
can be placed on the market as “fresh tomato catchup.” That the use of
oils is increasing is evident from the comparison of the ketchup of the
past season with that of former years.
[D] Brannt, W. L., A Practical Treatise on the Manufacture of Vinegar,
1900, p. 455.
When oil is used in ketchup, it is easily detected under the
microscope, as it appears in the form of shining, yellow globules which
blacken gradually when treated with osmic acid. Besides this, the oil
comes to the surface of the ketchup, where it can be seen readily, and
if considerable oil has been used a distinct layer is formed. When
the ketchup has been made for some time, the oil changes so that the
ketchup has a peculiar “greasy” odor, or the oil may be so changed as
to give a decidedly rancid smell to the ketchup. Oil usually causes a
deterioration in flavor and odor, though some of the ketchups to which
it has been added do not spoil readily. Olive oil, cottonseed oil,
and oleomargarine are used. That the oil is not considered one of the
regular known ingredients of the ketchup is shown by the failure to
declare its presence on the label.
To test the antiseptic value of oils in ketchup, experiments were
made, using olive oil, cottonseed oil, and oleomargarine in the
proportions of 1 part of oil to 1,000, 750, and 500 parts of ketchup,
respectively. The ketchup was made in small quantities, 2 gallons
for each experiment. After bottling, all except the check bottles
were inoculated with Penicillium and kept at kitchen temperature. All
spoiled, and neither the quantity nor kind of oil used had any marked
effect in preventing spoilage. That the oils affected the development
of the mold was evident. The mold developed first at the junction of
the ketchup with the bottle forming a ring which spread gradually over
the surface developing a somewhat heavy mycelium. This remained white
longer than usual, spores forming very gradually, as indicated by the
change in color from white to a delicate blue. At the end of three
weeks only spots of color appeared on the surface and these were still
blue, though in ordinary development the blue color changes to green in
two or three days.
Another test was made, using olive oil only, and in the proportions of
1 part of oil to 500, 400, and 300 parts, respectively, of the ketchup.
Reduction was made in a steam-jacketed kettle, the oil being added
when the ebullition of the ketchup was the strongest, after which the
boiling was continued for fifteen minutes. The ketchup was bottled,
unsterilized bottles being used, then covered loosely with the metal
caps.
The time required for the ketchup to spoil was longer than in the first
set, but there was not sufficient difference nor enough uniformity in
the time to indicate that the use of oil in ketchup is desirable, even
if the change of flavor and odor be not taken into consideration. The
average number of days before spoilage for those containing 1 part of
oil to 500 parts of ketchup, was thirteen and two-thirds days; one
has not yet spoiled (a period of forty-five days), while the first
bottle spoiled in four days. Those having 1 part of oil to 400 parts
of ketchup had an average life of nine and three-fourths days, the
minimum being three days, and the maximum twenty-six days. Those having
1 part to 300 parts of ketchup on an average did not spoil for six and
three-fourths days, the minimum being four days, and the maximum eleven
days.
The failure of some of the bottles to spoil, though similar in every
known respect to those which did spoil, is a feature peculiar to
ketchup and is familiar to manufacturers who make careful tests before
putting their product on the market. For this reason a rather large
number of bottles should be used in a test in order that the results
may be approximately accurate and represent general conditions.
STUDY OF PENICILLIUM IN KETCHUP.
Penicillium is a plant which is distributed widely and apparently is
able to grow wherever organic matter is found, though flourishing
best when the material contains acid. It causes loss in canneries,
breweries, distilleries, etc., the only use made of it being in the
manufacture of Roquefort cheese, the immature cheese being inoculated
with the conidia for the effect the mold produces in the maturing
process.
[Illustration: Fig. 1.--Conidia, Normal Size and in Various Stages of
Germination, Some with Branching Hyphæ (× 325).]
[Illustration: Fig. 2.--Conidiophore, Showing Unusually Large
Development of Conidia, from Culture in Moist Chamber (× 325).]
PENICILLIUM.
[Illustration: Fig. 1.--Conidia and Hyphæ from Culture in Experimental
Ketchup Containing One-sixteenth of One Per Cent of Sodium Benzoate (X
325).]
[Illustration: Fig. 2.--Conidia and Hyphæ from Cultures in Experimental
Ketchup Containing One-tenth of One Per Cent of Sodium Benzoate (X
325).]
CULTURES FROM KETCHUP PRESERVED WITH SODIUM BENZOATE.
DEVELOPMENT.
In developing, the mold forms a white felt-like mass, covering the
medium on which it is growing; then as development proceeds, it changes
to bluish-green, and finally to a darker, duller color. The change in
color is accompanied by a change in structure, the surface becoming
powdery in appearance, a slight current of air being sufficient to
dislodge a cloud of fine dust. This fine dust is formed of small,
spherical bodies, the spores or conidia (from the Greek meaning
_dust_). These need no resting period, but are able to develop at
once. When the conidia lodge on a moist substance they swell to a much
greater size and then send out a tube from some part of their surface.
The tube lengthens and septa form, dividing the tube into sections, or
cells. At the same time branches are sent out, which again form other
branches. The original conidium sends out a second branch shortly after
the first one, and usually from the opposite side, and may even send
out a third one. The formation of the septa and the subbranching goes
on in all, so that in a short time the branches mat together and form a
felt-like cover.
REPRODUCTION.
After a shorter or longer period of development, dependent on the
conditions, branches are sent perpendicularly from the substratum, and
into the air. These branches cease their growth in length, sending
out branches near the tip, which take the same general direction as
the original branch. Each of these subbranches is called a sterigma
(from the Greek word meaning _support_). In vigorous development the
sterigmata may form secondary branches, the whole forming a tassel-like
arrangement. The tip of a sterigma enlarges, a septum forms around the
enlargement, cutting it off from the sterigma, and forming a conidium.
The sterigma develops to the original length and another conidium is
formed, the operation being repeated many times, thus forming a chain
of spores. As the other sterigmata are also forming conidia in the same
manner, a series of these chains is formed close together. After the
cessation of conidial development, the filament below the sterigmata is
disorganized, setting free the conidia. The filament and head together
are called the conidiophore (Greek, dust-bearer).
Penicillium forms spores sexually, but the conditions for their
formation are unknown. Brefeld obtained them by growing the mold on
damp bread placed between two glass plates, and excluding the air.
Lindner obtained carpospores on a wort gelatin culture in a petri dish,
from which the air was excluded. The writer has tried various methods
for obtaining carpospores, but so far without success. Moist chambers
were used with various media, excluding the air. The development of
the mold is seemingly dependent on the amount of air in the chamber
at the time of sealing. After the air is exhausted, the conidiophores
assume fantastic forms, developing only one or a few sterigmata, and
on these one or few conidia. In other cases the conidiophores are
fascicled, in no cases, however, forming the conidia as luxuriantly
as when air is supplied. The hyphæ become clear, much vacuolated,
and develop more septa, and some of the cells become much enlarged.
An enlarged cell will often contain two or three septa, thus forming
cells that are not larger than disks. In cultures from which the air
was excluded from the start, no development took place. In test-tube
cultures sealed with paraffin after twenty-four hours, the mold
developed on the surface of the gelatin, forming a felted white mass,
but no conidia nor carpospores were formed.
GROWTH IN KETCHUP.
The form of Penicillium which was used in the experiments was isolated
from ketchup in which it grew luxuriantly. When conidia are first
formed on the ketchup, they are a delicate blue in color; they then
become bluish green, then green, and finally olive. The development of
the color of mold growing on ketchup is practically the same as when
grown in wort, tomato bouillon, pea bouillon, or gelatin made with
these solutions as a basis. In ketchup containing sodium benzoate, the
blue color appearing first remains for a long time, and in old cultures
the mold is a dull drab, not olive, as in normal development.
In ordinary ketchup made without a preservative, the mold forms a
heavy, wrinkled mycelium, showing a large development of conidia. In
the bottles of ketchup, the mold pushes down into the ketchup, becoming
entirely submerged, a clear liquid covering the mold and separating it
from the ketchup. This occurred in more than one hundred bottles. No
secondary mycelium formed on the surface of the liquid, a method of
development which frequently occurs in ordinary media when a mass of
mold is submerged.
An exception to this was shown in ketchup which had developed the mold
in the laboratory. The bottles were then put in the refrigerator for
two weeks. During this time scarcely any development took place; but
after they were again placed in the laboratory, the mycelium pushed
down into the ketchup and a new, very thin mycelium developed on the
surface. The filaments when seen under the microscope were swollen, had
irregular outlines, and a comparatively smaller number of septa, and
were filled with a coarsely granular protoplasm. The ends were blunt
and misshapen and the sterigmata were irregular, tending more toward a
fasciculated arrangement, and forming fewer conidia. The filaments from
the vinegar and acetic acid media had the same appearance as those
developed on ketchup, but had a smoother outline.
TEMPERATURE TESTS.
The limits for the germination of Penicillium, as given by W. J.
Sykes,[E] are 2° to 43° C. (35° to 110° F.), and the most favorable
temperature 22° to 26° C. (72° to 79° F.). This author states also that
according to Pasteur the dry spores retained their vitality at 108°
C. (226° F.), but that they were soon killed when immersed in boiling
water. Klöcker[F] quotes Pasteur as saying that the conidia are killed
if exposed to a temperature of 127° to 132° C. for half an hour, but
that they retain life at 119° to 121° C.
[E] Principles and Practice of Brewing, 1907, p. 284.
[F] Ibid., p. 281.
A series of tests was made to determine the thermal death point of
the moist and dry conidia of the Penicillium used in the experiments,
a young, vigorous development on ketchup being used. The flasks were
kept under observation for a month after the tests were made, as in
many cases a development does not occur in the usual time. The high
temperatures applied for longer periods of time were tried first, but
both temperature and time were reduced as results from the series were
obtained. Only the conditions obtaining in the final tests are given in
the table. It was found that the Penicillium used did not have the high
resistance supposed.
The tests were made in small flat-bottomed 10-cc flasks, tomato
bouillon being used for the tests on moist conidia. The bouillon was
used so as to have the conidia in a nutritive medium after the test was
made, without transferring. The time for those at 100° C. was estimated
from the time of ebullition. At the end of the specified time, the
flasks were cooled promptly under running water. As the flat bottoms
gave comparatively large surface, the heating and the cooling could be
effected in a short time. For the tests below 100° C. a vessel of water
was heated to the desired temperature, and the flasks were immersed in
it and shaken constantly. The dry conidia were placed in test tubes
which were immersed in boiling water for the desired time and cooled
under running water, after which 10 cc of sterilized tomato bouillon
was added. After determining the death point in this manner and finding
it to be much lower than had been supposed, it was decided to make the
test again, but using ketchup as the medium. Ten grams of ketchup were
sterilized, then inoculated from a vigorous growth of mold, and tested
with a set in which the tomato bouillon was used. For those below 100°
C. the two flasks which were to receive the same temperature were held
in the vessel of water at the same time, so that as nearly as possible
the treatment would be identical. The following results were obtained:
_Thermal death point of moist and dry conidia of Penicillium._
PENICILLIUM IN 10 CC OF TOMATO BOUILLON.
-----------+------------+----------+------------+---------------------
No. of |Temperature.| Time of |Time before |Period of observation
experiment.| | heating. |germination.| and developments.
-----------+------------+----------+------------+---------------------
| _°C._ |_Minutes._| _Days._ |
1 | 85 | ½ | 3 |Dark strings from
| | | |spores; 9 days;
| | | |no development.
2 | 80 | 1 | |
3 | 75 | 1 | |
4 | 70 | 5 | |
5 | 65 | 5 | 3 |Dark strings running
| | | |from spores; 9 days;
| | | |growth normal, spots
| | | |on surface.
6 | 60 | 5 | 3 | Do.
7 | 55 | 5 | 3 | Do.
-----------+------------+----------+------------+---------------------
PENICILLIUM IN 10 CC OF KETCHUP.
-----------+------------+----------+------------+---------------------
1 | 100 | 3 | |
2 | 100 | 2 | |
3 | 100 | 1 | |
4 | 100 | ½ | |
5 | 100 | Instant.| |
6 | 85 | ½ | 2 |Colonies on sides;
| | | |8 days; surface
| | | |covered, green.
7 | 80 | 1 | 2 | Do.
8 | 75 | 1 | 2 | Do.
9 | 70 | 5 | 8 |Colony on surface.
10 | 65 | 5 | 9 | Do.
11 | 60 | 5 | 3 |Colonies on sides;
| | | |8 days; surface
| | | |covered, green.
12 | 55 | 5 | 4 | Do.
13 | | | 2 |Ring around sides;
| | | |3 days; surface
| | | |nearly covered.
-----------+------------+----------+------------+---------------------
DRY CONIDIA.
-----------+------------+----------+------------+---------------------
1 | 100 | 10 | 4 |Rough appearance,
| | | |like that in ketchup.
2 | 100 | 15 | 4 | Do.
3 | 100 | 20 | 7 |Slight growth.
4 | 100 | 25 | 10 |Growth barely
| | | |perceptible.
5 | 100 | 30 | 10 | Do.
6 | 100 | 35 | |Conidia stained
| | | |readily, showing they
| | | |were dead.
-----------+------------+----------+------------+---------------------
YEAST.
-----------+------------+----------+------------+---------------------
1 | 55 | 5 | 2 |Wrinkled film; liquid
| | | | turbid.
2 | 60 | 5 | 2 | Do.
3 | 65 | 5 | 2 |Thin, smooth film;
| | | |liquid clear.
4 | 70 | 5 | |
5 | 75 | 5 | |
6 | 100 | Instant.| |
-----------+------------+----------+------------+---------------------
The moist heat was very effective in destroying the vitality of the
conidia of Penicillium, the death point being 27° C. higher than the
maximum temperature for germination as given by Sykes. The heating was
more effective in destroying germs when applied to bouillon than to
ketchup, no development taking place for any temperature above 65° C.,
even when applied for a short time.
In the ketchup the lower temperatures for the longer periods of time
were more effective in checking the development, even though they did
not destroy the vitality. In the ketchup, with the exception of Nos. 9
and 10, the colonies started invariably along the sides of the flasks.
The greater access of air to those on the sides would account for
this. The conidia on the sides of flasks Nos. 9 and 10 must have been
destroyed, as no development took place in either case except in the
center of the surface.
The dry conidia were destroyed at 100° C. when heated for thirty-five
minutes; they did not reach a normal development in any case, even
when heated for only ten minutes, many of the conidia being destroyed
by this treatment. Where development failed to take place, the conidia
were stained with a water solution of eosin, so as to be sure that the
effect was death, and not an arrested development.
The results of the tests do not agree with those obtained in factory
practice, where the ketchup is cooked at 100° C. for at least forty
minutes and sometimes for fifty or fifty-five minutes, depending on the
consistency of the pulp.
HISTOLOGICAL STRUCTURE OF KETCHUP.
In ketchup are found parts of all the various tissues of the tomato
broken into fine pieces by the action of the cyclone. Although the
sieves take out the seeds, skins, and any large pieces, particles of
the various tissues are present in size sufficient for identification.
Among the distinctive features are the red crystalline bodies in
the parenchyma, which serve to a certain extent to distinguish
the parenchyma from that of other plants which might be used for
adulteration, and serve also to differentiate the natural from the
artificially colored ketchup. Some of the red dye used colors all
protoplasm indiscriminately, even that of the fungi present, and as
a colored ketchup is usually poor stuff, containing many fungi, the
mold filaments, yeast cells, and bacteria receive their share of the
color. Other red dye used is in the form of fine powder, which does not
go into solution, but is distributed as irregular particles which are
distinct from the red crystalline bodies.
Good ketchup made from whole tomatoes has a clean appearance readily
distinguishable under the microscope; but the poor ketchup has usually
a superabundance of fungi present, fully developed colonies of mold,
many forms of conidia, besides yeast-like cells, and different forms
of bacteria. All of these may be dead, but neither preservatives nor
dosage of odorous spices can disguise their presence. In some of the
ketchup examined, which was put up in attractive form and labeled
as being made from the whole tomatoes, and which had the appearance
and odor of good ketchup, the microscope showed the presence of such
quantities of fungi as to leave no doubt that the tomatoes were spoiled
when cooked. It is presumable that some of the dealers placing this
sort of stuff on the market do not know its condition themselves, and
either buy their pulp from other factories or trust its manufacture to
employees whose only care is that the ketchup shall have a bright color
and shall “keep.” Some of the mould filaments and conidia are distorted
in the same way as those of the Penicillium are when grown in ketchup
to which sodium benzoate has been added.
The ketchup made from sound tomatoes and manufactured in a cleanly
manner has practically no fungi present. The ketchup that was used in
these experiments was made at different times during the season and was
of this character, no bottle examined showing mold filaments when first
opened.
MICROSCOPIC EXAMINATION OF SOME COMMERCIAL BRANDS.
In examining ketchup the color, odor, amount of discoloration,
presence of foreign tissue, foreign coloring matter, oil, and fungi
were determined. If no preservative was mentioned, some of the ketchup
was put in petri dishes and inoculated with Penicillium to determine
whether growth could take place. The following examinations are
reported, as they represent some of the best known brands on the market:
_No. 9._--Opened September 2, 1907; age unknown; pint bottle; no
preservative mentioned; not spoiled July 6 of following year.
This ketchup was guaranteed to be made from fresh, ripe, tomatoes
by a new process. The color is an unnatural red, has not faded,
and the odor is good. The microscope showed the presence of much
refuse, and large quantities of fungi, whole colonies of molds,
the filaments distorted, many yeast cells, and bacteria. The red
color was not confined to the red crystalline bodies, as is the
case in ripe tomatoes, but the whole of the protoplasm of the
cells, including the nucleus and nucleolus was red, as were also
most of the mold filaments and yeast, indicating the presence of
considerable artificial coloring matter. The structure indicated
that the stock had been manufactured from “trimmings,” and
further, that they were not fresh when used, but had fermented.
There was no oil present. The “new process” is a success in
keeping ketchup, as no preservative is mentioned. The price was 20
cents.
_No. 112._--Another bottle of the same brand of ketchup; examined
in April, 1908; presumably manufactured in 1907; one-twelfth of
1 per cent of sodium benzoate declared on label; a bright red;
guaranteed to be from fresh ripe tomatoes and uncolored. The
microscope showed no dyeing of the tissues, few fungi, and no
extraneous matter. The price was 20 cents.
_No. 17._--Opened September 28, 1907; age unknown; a pint bottle;
sodium benzoate declared on supplemental label, no amount being
stated; reddish brown color, badly discolored on top; greasy odor;
not spoiled July 6, 1908; refuse present; large amount of oil;
many fungi; the mold filaments enlarged and distorted. The price
was 15 cents.
_No. 109._--Another bottle of the same brand examined in April,
1908; presumably manufactured the preceding year; had one-tenth
of 1 per cent of sodium benzoate; not spoiled July 6, 1908;
reddish brown color, discolored near top; greasy odor. This was
practically the same as the first bottle examined, had fewer mold
filaments, but many bacteria.
_No. 18._--Opened September 28, 1907; age unknown; pint bottle;
no preservative mentioned; not spoiled July 6, 1908. A neck label
stated that it is made from sound ripe tomatoes and uncolored.
Color reddish brown; greasy odor; many oil globules; too many mold
filaments and bacteria for sound tomatoes. Price 20 cents.
_No. 113._--Another bottle of the same brand examined in April,
1908; said to have been manufactured in 1908; no preservative
mentioned; not spoiled after standing open for seventy days; same
as No. 18 in color and odor; oil and many fungi again present.
_No. 10._--Opened September 2, 1907; age unknown; half-pint
bottle; no preservative mentioned; not spoiled July 6, 1908. A
neck label 2 inches in height guaranteed the highest quality; an
extra label lower down on the neck stated the product to be the
natural color, and made from fresh, ripe tomatoes; the regular
label carried the brand, manufacturer’s name, etc. Color brown;
sweetish odor; colonies of mold; distorted filaments; many
bacteria; a few small oil globules. Price 25 cents.
_No. 106._--Same brand; pint bottle; examined in April, 1908; said
to be manufactured in 1907; color red, discolored near surface;
2-inch neck label in addition to regular label; no preservative
mentioned; did not spoil in seventy days; oil globules; particles
of red, amorphous matter; whole colonies of mold, as well as
fragments of filaments; teeming with bacteria.
_No. 77._--Different brand, but same manufacturer as Nos. 10 and
106; age unknown; pint bottle; one-twelfth of 1 per cent of sodium
benzoate declared; opened December 1; placed in incubator at 95°
F. for a month; not spoiled July 6; color reddish brown; greasy
odor; oil globules, many mold filaments, and bacteria present.
Price 20 cents.
_No. 107._--Third brand from same manufacturer as preceding; said
to be manufactured in 1907; half-pint bottle; one-twelfth of 1
per cent of benzoate of soda declared; layer of oil on surface;
sweet odor; reddish-brown color. Oil globules prominent feature
microscopically, whole colonies of distorted mold were present,
and sample contained many different forms of bacteria. Price 10
cents.
_No. 14._--Opened September 2, 1907; age unknown; no preservative
mentioned; not spoiled July 6, 1908; half-pint bottle; color red;
good odor; few bacteria; free from refuse. Price 25 cents.
_No. 108._--Same brand as No. 14; said to be manufactured in 1907;
pint bottle; one-tenth of 1 per cent of benzoate of soda declared;
color red; good odor; few fungi; clean and free from refuse.
_No. 33._--Opened October 24, 1907; age unknown; one-tenth of 1
per cent of benzoate of soda declared; spoiled November 1; pint
bottle (14 ounces); sweetish odor; brown color; many molds, yeast
and bacteria. Price 10 cents.
_No. 114._--Same brand as No. 33; said to be manufactured in 1907;
opened in April; not spoiled in seventy days; many molds, yeasts,
and bacteria; some green tissue, and filaments of algæ. The price
was 10 cents.
SUMMARY.
1. The experiments made during the season of 1907 on the manufacture
of tomato ketchup without chemical preservatives were conducted under
factory conditions and upon a commercial scale. The results prove that
such a ketchup can be made and delivered to the consumer in perfect
condition; the product in question having already stood ten months,
unopened, without showing the slightest indication of spoilage.
2. The product is of excellent consistency, flavor, and color. The
formula employed regularly in the factory where the experiment was
conducted was used, but other recipes could be adapted without changing
the character of special brands. In the manufacture of such a product
the following precautions were observed:
(_a_) Whole, sound, ripe tomatoes and high-grade salt, sugar, vinegar,
and spices were used; care and cleanliness were observed at every
step of the preparation, and the preservation accomplished by heat in
the following manner: The pulp was cooked in a steam kettle for about
forty minutes, until the mass was reduced to about one-half its volume.
Additional processing after bottling did not appear to be necessary to
keep the ketchup before opening, and had no effect in these experiments
in delaying spoilage after opening.
(_b_) Ketchup was bottled directly from the cooker at a temperature
of 205° F. in bottles prepared in two ways: (1) Sterilized in a steam
chamber at 230° F.; (2) Washed in hot water, rinsed, and heated to 190°
F. in a dry heat for at least thirty minutes. Ketchup was also bottled
after the usual process of sieving at 165° F. in bottles prepared in a
similar manner. The corks for all bottles were sterilized in a paraffin
bath at 270° F. The same ketchup which was bottled at 165° F. was also
given subsequent processing at 190° F. and 212° F. for twenty and forty
minutes. All have kept without spoilage.
3. Some of the condiments have a limited antiseptic value, but can
not be depended upon to prevent spoilage in the quantities used for
flavoring. While sugar and vinegar can be added in such amounts as
to delay the appearance of molds, and cinnamon and cloves can be
depended upon to check deterioration to some extent, these condimental
substances have only an incidental value for this purpose.
4. The spoilage of ketchup after opening depends more upon the
temperature of the place in which it is kept than on any variation
in the manner of processing. Fresh ketchup held, after opening, at a
temperature of 95° F. kept for five days on an average without any
trace of mold appearing; at 72° it kept for six days; at 67° for eight
days; about 46° (refrigerator), fourteen days; and at from 30° to 60°
for twenty-seven days. These figures represent the time at which the
first trace of spoilage occurred in the neck of the bottle--had this
been removed the figures would be much increased--and by no means
represent the maximum time during which the ketchup could have been
used, the maximum figures, even under these conditions of observation,
varying from eight to fifty-eight days. The keeping of the ketchup
in warm storage at 70° for one hundred and fifty days before opening
hastened the average time of spoilage after opening about one day. The
advisability of using small containers, to get the best results with a
first-class ketchup, is apparent.
5. Sodium benzoate, even when used in the proportion of 0.1 per
cent, is not always effective, and has an injurious effect upon the
living matter of the molds, shown by the distortion and swelling of
the filaments, which are filled with a coarse granular protoplasm
containing much fat.
6. Artificially colored ketchup can be detected under the microscope
by the fact that certain tissues, normally colorless, are dyed red, or
by the presence of fine, red, amorphous particles which do not go into
solution.
7. Ketchup made from whole ripe stock in a cleanly manner gives a clean
appearance under the microscope, but few molds, yeasts, and bacteria
being present. On the other hand, ketchup made from trimming stock,
or from tomatoes that have been allowed to spoil, contains immense
quantities of these growing organisms which may be killed in the
process of manufacture, but still give proof of the character of the
material used. Ketchup as ordinarily made from trimming stock should,
therefore, be designated, so as to differentiate it from that made from
sound fresh tomatoes, as the two products are radically different.
This exactness in labeling is due no less to the manufacturer than to
the consumer, as it is impossible to make the superior product in fair
competition with the inferior one, other conditions being equal, unless
the two are properly designated, there being naturally some difference
in the price.
Transcriber's Notes:
In the text version, italics are represented by _underscores_.
Missing or incorrect punctuation has been repaired.
The following corrections have been made to the text:--
p.8. A majority of the manufacturers employ word, has been changed to
A majority of the manufacturers employ the word.
p.28. one has has, the duplicate has been removed.
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