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Title: Ketchup - Methods of Manufacture; Microscopic Examination
Author: Bitting, K. G. (Mrs. Katherine Golden), Bitting, A. W.
Language: English
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Copyright Status: Not copyrighted in the United States. If you live elsewhere check the laws of your country before downloading this ebook. See comments about copyright issues at end of book.

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                         METHODS OF MANUFACTURE

                             A. W. BITTING

                        MICROSCOPIC EXAMINATION

                             K. G. BITTING

                            LAFAYETTE, IND.
                        MURPHEY-BIVINS CO. PRESS


This brief presentation of some facts concerning the manufacture of
ketchup and discussion of the methods for its examination is offered in
appreciation for the many favors shown to us by manufacturers. The text
has been kept as free from technical terms as the subject would permit,
and the results of observations and experiments covered by direct
statements instead of giving details and tables.

Nothing new is offered in the method of manufacture, but the doctrine of
the use of sound fruit, sanitary methods, and sterilization is
reiterated. The position taken upon the method of examination is not new
but it is thought proper to present something concerning this phase of
the work to the manufacturer.



Ketchup is a spiced sauce used for its condimental effect in imparting
flavor, or to give relish to other foods. It receives its distinctive
name from the base used, as, tomato, grape, currant, mushroom, walnut,

The terms ketchup, catchup, and catsup are used to designate any spiced
sauce and seemingly without any reason for the one used other than
personal preference. Though the derivation of the term has been
attributed to different sources by the dictionaries, there seems to be
more reason for the use of the term ketchup than for the others, both
upon the ground of its prior and more general use, and from the history
of its derivation. Murray[1] gives the derivation of ketchup from the
Amoy dialect of the Chinese, the term being =koechiap= or =ke-tsiap=,
meaning a brine of pickled fish or shell fish; and he states that the
Malayan =kechap=, which has been claimed as the original source, may be
from the Chinese, but that the word =kitjap=, as given by some
dictionaries from the Japanese, is an impossible word for that language,
and is possibly an error for Javanese. The term catchup given by some
dictionaries appears to be based on the assumption that the first
syllable ketch is a colloquial form of catch. Many manufacturers use the
word catsup, a spelling for which there seems to be no etymological
warrant. The earliest use of the term catsup, found by the writer, with
any particular significance attached to it as distinct from the other
two terms, is by Kitchiner, an English physician, in the Cook’s Oracle,
in which directions are given for reducing “catchup” to half the
quantity, the statement being that “it may then be called double cat-sup
or dog-sup.” The first edition of the book appeared in 1817 in England.


Footnote 1:

  Murray, J. A. H. New English Dictionary.


It is but natural that a product of this kind should vary greatly in
flavor due to the selection and quantity of spices, salt, sugar, and
vinegar used, and in consistency due to the degree of concentration and
fineness with which the base has been comminuted. Most of the recipes
for home-made ketchup call for rather liberal spicing and long cooking
so that they have a fairly heavy body. These insure good keeping
quality, but impart a dark color to the product.

The manufacture of ketchup upon a large commercial scale is of rather
recent development and is confined almost wholly to the use of tomatoes
as a base. There was little ketchup of the kind best known at present
made prior to 1890, as most ketchup was made by what was known as the
natural fermentation method, that is, allowing the tomato pulp to
ferment spontaneously and using the solid portion for stock. This method
was continued, though on a decreasing scale, until 1908, at which time
it was practically prohibited. Beginning about 1890, ketchup was made
from fresh pulp and barrel stock without fermentation, the fermentation
being prevented by the use of a preservative. The method is still in
use. The first extensive manufacture of non-preservative ketchup began
about 1908, though a few firms had been making it prior to that time,
the pioneer probably being E. C. Hazard, of Shrewsbury, New Jersey.

From the amount of space given to the subject of ketchup in the canning
and food journals, one might conclude that it is a difficult product to
make, or that it is one of very great importance. It is in reality very
easy to produce, but has assumed a prominence among food subjects which
it does not deserve, due to the fact that some manufacturers have not
yet learned the necessity for using care, or persist in using material
of questionable quality.

Ketchup is made in the home with very simple apparatus; a colander or
sieve for breaking and straining the pulp, and a copper, porcelain, or
earthen kettle for cooking, being all that is necessary. The cooking of
the tomatoes with the spices, sugar, vinegar, etc., is generally done
slowly, until a heavy body is obtained, which results in a dark color,
but insures sterility of the product when it goes into the container,
and also contributes to keeping quality after it is opened. In the
factory many refinements are necessary to make a commercial article
which will attract the eye as well as satisfy the sense of taste. The
usual dark colored, rough, home-made article will not command a sale
over a grocer’s counter alongside of that made in a modern commercial
kitchen. Here, sorting tables, washing machine, scalder, cyclone for
pulping, steam-jacketed kettle, tanks with coils, or vacuum pan for
cooking, finishing machine, bottle washing, and filling machine, are all
necessary. The pipes carrying the pulp from one machine or vat to
another must be enameled, bronze, tin-lined, or silver-plated to prevent
the fruit juice from coming in contact with iron or anything which will
cause discoloration. The work is done speedily, and the cooking done in
the shortest possible time in order to secure the brightest color and
smoothest consistency.

The stock should be whole, sound, ripe tomatoes, preferably grown near
the factory so that they may be delivered promptly after picking and
with the minimum injury. They should be picked when in prime
vine-ripened condition. Fruit picked when just turning and allowed to
stand one or two days to color will not have the same rich flavor as
when vine-ripened, but will stand rougher handling. Green fruit gives a
weak color, and over-ripe fruit is prone to become injured and spoil in
handling. The tomato should be through the process of manufacture within
twenty-four hours from the time that it is taken from the vine. Repeated
experiments have shown that rapid handling of fruits and vegetables
gives the best results for canning, and the tomato is no exception to
the rule when used for ketchup.

The variety of tomato used is of importance. The tomato will vary in
solids from less than 5.5 per cent to nearly 8.75 per cent; in soluble
solids from less than 3.5 to nearly 6.5 per cent; in sugar from about
2.25 per cent to 4.25 per cent; and in acidity from .3 per cent to .6
per cent. The colors will vary from an almost creamy white to a very
deep red with variations in yellow and purple. The only way to get
uniformity in a product is to select one good variety and discard
others. The preference is for a clear red smooth tomato of medium size,
firm, and of fair acidity. While color may be only “skin deep” as far as
being red, yellow, or purple is concerned, experience has shown that a
clear red variety gives a better and more lasting color than yellow or
purple. A medium sized smooth tomato is preferred because of less
adherence of dirt, fewer cracks, and generally more even ripening to the
stem. A fairly acid tomato imparts more flavor and needs less vinegar in
the finished product. The fleshy portion of the tomato gives the body,
but the pulp about the seeds furnishes the characteristic flavor.

The collecting of tomatoes in the field should be done at short
intervals so that the fruit may be taken when in prime condition. Where
picking is done at too wide intervals, there is a tendency to take fruit
that is only colored and not really ripe, and for some to be left and
become over-ripe. In both cases the manufacturer is the one to suffer,
by increasing the expense of sorting, holding the green if he is to make
a high grade product, and by waste from cracking and mashing of the
over-ripe. The stems should be left in the field, as they increase the
weight and may injure the product to a certain extent.

The handling should be in shallow crates. These should have strong
cleats across the ends so that one may be placed above the other without
touching the fruit, and if of considerable length, should have a
partition. The cleats permit space for ventilation in case they must be
stacked for a few hours or more. The depth should be such as not to
permit more than three or four layers of fruit. The deep box and the
conical basket are not well suited as carriers and should not be used
unless delivery can be made by wagon direct from the field and within a
few hours after gathering. It is the rule to see cars and barges loaded
with baskets arrive at the factory with more or less of the fruit in bad
condition. When one basket is set on the edges of two or three others in
stacking, there is always cutting of a few of the top fruit, the
movement in riding causes others to gradually settle and pack into the
cone shape of the bottom, so that if they be held for a day or more,
there will be loss of juice, consequent growth of mold, and
contamination of the sound fruit from the infected. The actual loss from
this form of handling has not been determined, but is undoubtedly much
larger than is generally supposed. It is the belief of the writer that
the loss is not far from 10 per cent. It is certainly much greater than
the difference in the cost of freight and handling of the box over the
basket. All baskets and boxes become more or less infected with mold
during the season and this spreads to the fruit, the contamination
increasing the longer the fruit is held, the tighter it becomes wedged
together, or the greater the cracking. The shallow crate affords the
better protection.

When tomatoes arrive at the factory, they should be purchased by weight
for =sound= fruit. Buying by the box or basket is antiquated and not
satisfactory to either buyer or seller. Under the recent Federal net
weight law, purchase by basket or crate must show on each container the
exact weight or measure if there be interstate shipment, and the same is
true for some of the states. It should not be necessary to give more
than a general inspection at the factory. A contract for ripe fruit at
ten dollars per ton, which, when delivered, requires sorting, and the
holding of unripe and the discarding of defective fruit, is equivalent
to ten dollars, plus all the additional cost in labor and the loss in
making it fit for use.

If it be necessary to hold the tomatoes for some time at the factory
before manufacture, the crates should be stacked in tiers with a foot or
more of space between each tier for the circulation of air. Stacking the
tomatoes in solid blocks affords the ideal condition for the increase of
molds. There can be no doubt that large quantities of fruit have been
lost each year from neglect of this simple precaution. Recently a method
of holding in water has been originated by Mr. E. W. Grosvenor, at
Paoli, Indiana, and consists in using large tanks capable of receiving
500 or more bushels in which tomatoes are submerged in cold water as
soon as received, and then held until they can be used. The device is
based upon the theory that the tomato skin is practically impervious to
water, also that the molds require air for their development and by
submergence in water their activity would be lessened.

These tanks are made with false bottoms to receive the sand and dirt,
are provided with jets to supply fresh water and to cause the tomatoes
to automatically feed upon the conveyor. The first impression is that
the tomatoes are soaking in rather dirty water, but tests show that they
absorb very little, if any, water, and examination at every stage shows
them to be washed cleaner than by the usual method. The work has not
been carried far enough to be conclusive, nor to indicate its

Experiments made to duplicate the factory conditions, comparing air and
water storage for short periods, were decidedly favorable to the latter.
Much less change occurred in water storage for twenty-four to
forty-eight hours than in the air, and there was the further advantage
that the tomatoes were washed freer from dirt, sand, and mold, and that
rot was cut out better under the water sprays. Some lots of tomatoes
were held as long as eighty hours, but this is not to be recommended.
When rotting does occur under water, it is of a different character from
that in the open and is far more offensive.

If tomatoes be accepted at the factory in a mixed condition, that is,
greenish, ripe, and over-ripe, they should be passed first over a
sorting belt and preferably one which will turn all sides of the fruit
to the inspectors. The green fruit should be held out in separate crates
to ripen, and the unfit fruit be discarded. If green fruit be not
accepted, the inspection can be done better after washing. In any event
the fruit must pass slowly on the table and in single layers. No
inspection can be made adequate if the tomatoes pile on the belt two or
three layers deep, or pass at such a rate that the eyes tire and all
look alike. This is a place where more belts moving slowly, and fewer
persons working on each belt, will give the better results. Hand sorting
is essential and far more important than in tomato canning. In the
latter the defective parts are cut away, but no machine has yet been
devised to make the separation complete in making pulp or ketchup.

One other point in inspection is the removal of the stems, which should
be the duty of the pickers, but which is often neglected. If the ketchup
is to have the brightest, cleanest color, the removal of the stem is
advantageous and, furthermore, if the tomatoes are raised on sandy
ground, there may be enough sand held around the stem to make
appreciable grit. Some manufacturers leave the stem on to give flavor.


The washing is the most important mechanical operation in making pulp or
ketchup in order to get a clean product. It is the weak spot in most
factories, but fortunately is the one that can be most easily changed.
The ideal washer is one that first receives the tomatoes in a tank,
holding them for a sufficient length of time to soak and to loosen the
dirt, and then submits all parts to a thorough spray under strong
pressure. Most washers do not meet these requirements. In many cases the
tomatoes are either not dropped into water, or go in and then out again
so quickly that they are only made wet and bright, but not clean, then
pass under a few cross-sprays, each of which does not deliver a stream
more than an inch or so in width, the total spraying not being active
over a space of more than six inches and only from above. Some machines
do not actually spray the fruit more than one or two seconds. In some
cases, it is not so much the fault of the machine as that of the owner
in over-speeding and over-loading it. Most machines use a sufficient
volume of water, but not under sufficient pressure, nor over a
sufficient area. One of the best washers in use is a slight modification
of the cylindrical washer used for removing the lye and peel from
peaches. It consists of a cylinder about two feet in diameter and twelve
feet long, made of a specially corrugated iron. The corrugations are
sharper than the ordinary pressed metal used for building and siding,
and in addition they are perforated at frequent intervals. This cylinder
is mounted on a slight incline. The tomatoes are fed in at one end and
the revolving motion causes their discharge at the other. The effect of
the corrugation is to cause each tomato to turn over and over in its
course and thus avoid all sliding. A spray pipe passed through the
entire length and, when provided with the proper nozzle, insures a
thorough washing, the tomatoes being under actual sprays from six to
twenty times as long as in many machines that are now in use. The water
pressure should not be less than sixty pounds per square inch and is
better above one hundred pounds if fine perforations or nozzles be used.
In nearly every case it is necessary to augment the natural pressure by
an auxiliary pump. The principle of the strong pressure is seen in using
a hose without a nozzle to wash a floor and one with a nozzle and strong
pressure. In the former case it does not clean, while with the latter it
does and with less water. The washer just described is too vigorous for
tomatoes for canning, as the treatment is too rough. If the tomatoes are
soft or badly cracked, it causes considerable loss, but not of material
that should be used in ketchup. The strong sprays will also cut off
adherent mold and soft rot. A thoroughly good washer will do about
nine-tenths of the work for the inspectors. During the past season some
modifications have been made of this washer in the east. The machine has
been enlarged, but better results would be obtained by using a greater
number of small ones. Again, some washing machines have been
ineffective, not on account of any defect, but because of over-speeding.

The vigor with which the washing is done is always apparent in the
finished product. The poor washing usually given to tomatoes for
canning, accounts in a measure for the relatively large numbers of
organisms found in ketchup made from trimmings.


After washing, the tomatoes may be reduced to a pulp in one of three
ways: by running the raw tomatoes directly through a grinder and into
the cyclone; by passing the tomatoes through a scalder and into the
cyclone; and by turning the tomatoes into jacketed-kettles or tanks and
cooking them until soft before running through the cyclone. There is a
difference in the product obtained by these methods. The first one gives
a somewhat larger yield, as the hard parts are cut and torn so that more
will be squeezed through the sieve. The color is generally stronger and
inclined to the purple side rather than the yellow. The color, however,
does not hold so well when exposed to light. The pulp inclines to froth
and there is a marked separation of red pigment on the top. A raw pulp
will begin to separate into a clear layer below and solids at the top in
about fifteen to twenty minutes after standing in a tank. This is due to
the air incorporated in the solids and possibly to difference in
specific gravity, and not to fermentation, as frequently alleged.
Changes will take place more rapidly in such pulp than in that made from
scalded fruit.

There is not a great deal of difference between the second and third
methods, the object in both cases being the same. If a long scalder be
used, the skins will be loosened and the tissue softened so that it will
be easily separated from the green parts, hard cores, or black rot.
There will be no acquisition of color from the stems to discolor the
ketchup. The loss is a little heavier in scalder heating than where the
fruit is cooked in the tanks, but there is the compensation that there
is less carrying of hard or objectionable material. A scalder to be
effective should be much longer than that used in canning, or a greater
volume of steam should be used. The tomatoes should be heated to about
180 deg. F. There is little choice in the two methods, but the
preference is with the scalder, both being preferred to the raw ground
fruit. A pulp made in this way separates slowly and there will be no
material increase in organisms for a rather long time (three or four
hours). There is less separation of pigment on cooking and there is a
clean look to the tissue under the microscope.

In making pulp it is important that the paddles in the cyclone be held
back from the screen and the juice driven through by centrifugal force
rather than by hard grinding. When kept well back, the green butts,
cores, and tissues which have been hardened by brown mold are carried
over the end so that there will be fewer black specks in the finished
pulp and it will have a better appearance under the microscope.

The pulp should be conveyed immediately from the cyclone to the cooking
kettle, and the next operation begun at once. A storage tank is
unnecessary when there is large cooking capacity, and in most cases it
is a source of trouble rather than a help. A sample should be taken as
soon as the batch is drawn, and the specific gravity determined so that
the proper quantity may be used to give a finished product of uniform
consistency. Assuming that 500 gallons of pulp will give a normal
finished batch, if the tomatoes are watery, it may require 550 gallons
or more to give the same result when concentrated. This is easily
calculated from the specific gravity so that reasonably uniform results
may be obtained. Samples should also be tested for acidity once or twice
each day so that the addition of vinegar can be governed accordingly.
The concentration of pulp will vary from 40 to 60 per cent depending
upon its condition and the weight of body desired.


The cooking is done in copper-jacketed kettles, in glass-lined metal, or
in wooden tanks, the tanks being heated with coils. The glass-lined tank
has the advantage of very little metal coming in contact with the pulp
and can be kept cleaner than wood. A question has been raised regarding
the suitability of copper for a cooking utensil, though no positive
objection has been made. The vacuum pan is coming into use for
concentrating pulp, but has been little used in making the finished
ketchup. The jacketed-kettle is used by most manufacturers, though the
tank and coil is being adopted by those who wish to make large batches,
as it is the more economical. Agitators are no longer used, as by proper
handling of the steam and automatic traps, little burning occurs on
either kettles or coils. The efficiency of the open tank or kettle is
increased by providing a strong exhaust or suction for the air at the
back and just above the top of the kettle. A swiftly moving current of
air across the top of the kettle will carry off the steam and shorten
the time of heating from ten to twenty per cent.

A pulp may be reduced in a vacuum pan in about one-fourth the time
necessary in the open kettle and with a marked conservation of color and
flavor. The vacuum pan may be used for quick reduction and the finish be
made in open kettles in order to apply the heat long enough to spice and
to sterilize. There are possibilities along these lines which have not
been developed.

The time of cooking a batch of ketchup will depend upon the equipment
and the consistency of the finished product. With a good kettle or coil
and ample steam-supply a batch should be completed in from thirty-five
to forty-five minutes. This gives sufficient time to get the most
desirable flavor from the spices and is not so long as to result in


The selection of the spices depends entirely upon the flavor desired.
Cinnamon, cassia, cloves, allspice, mace, pepper, paprika, cayenne
pepper, mustard, ginger, coriander, bay leaves, caraway and celery seed,
are all to be found in the various formulae. Some manufacturers spice
lightly in order to retain the maximum of the base flavor, while others
go to the opposite extreme on the misguided assumption that they will
act as preservatives. The quantity used should be determined by the
flavor desired and upon no other consideration. The spices may be used
whole, ground, or in some cases as acetic acid or oil extracts. The
whole spices are preferred by nearly all the manufacturers of high grade
goods. They are more expensive, but give a different flavor from the
extracts. The spices are weighed for each batch and are tied in a bag or
placed in a wire basket and suspended in the kettle while cooking. Some
use very large quantities and cook from only ten to twelve minutes in
order to get a distinctive flavor. This is very expensive, as only a
small quantity of the flavoring matter is extracted in such a short
time. One of the serious objections to the use of the whole spices is
that they may darken the ketchup and also cause some discoloration in
the neck of the bottle. For that reason, black pepper and allspice in
particular are being discarded, and oil of cloves is being used in part
for the whole berries. The grade of the spice will also have an effect,
the cheap stock being unsuitable for a bright clean product. Small
quantities of ground cayenne pepper are used as a substitute for the
black pepper.

Acetic acid extracts of some of the spices are being used to a certain
extent, but they have a peculiar harsh flavor that makes them
undesirable. The oil extracts can be used to only a very limited extent,
as they impart a flavor suggestive of the drug store.

One method of making a nearly complete extraction of the spices is to
place them in their proper proportion in vinegar a few weeks before the
ketchup season begins and then add the spiced vinegar in the proper
proportion to each batch. The result is different from that obtained by
cooking, and the method is not recommended for first grade goods.

The waste of spices in the usual process of manufacture is indicated by
some work done by Mr. H. E. Bishop of the laboratory of the Indiana
State Board of Health. He found that in making ketchup, when the boiling
was kept up for thirty minutes, that only 27.8 per cent of the oil of
cassia, 11.5 of the oil of cloves, and 33.3 per cent of the oil of
allspice were extracted. (Unpublished report.)

Paprica rosen, Hungarian, or sweet paprika, is used for coloring
purposes, though it parades as a spice. This is a mild variety of
Capsicum annuum, one of the species of the genus Capsicum, from which
cayenne pepper is made. The variety offered to manufacturers has a more
intense red color and much less pungency than the ordinary paprika. This
paprika can be obtained as the bright fruit, ground dry, or in oil. In
the latter, it is said, that part of the capsicin is removed, also that
the oil sets the color in inferior material. The oil is of a
reddish-yellow color and the large number of globules and irregular
masses serve to distinguish it from cayenne pepper. It fulfills the
claims of the importers—“coloring the ketchup, not adding materially to
the pungency, and coming inside the laws in being one of the regular
ingredients.” It requires just about sixteen times as much as would be
required of ordinary paprika to get the same flavor. Considering the
cost, in the relative proportion required, there can be little doubt of
its real purpose. It will conceal inferiority to ordinary observation in
that it gives a red color where otherwise a muddy color might be
present. The color does not have durability, and it is easily recognized
under the microscope.

Onions and garlic are added in varying quantities and may or may not be
kept in the batch throughout the whole cooking period. Considerable
difference in flavor is apparent with the length of time of the cooking.
Chili peppers are also used in hot ketchup or cocktails.

Vinegar is added to nearly all ketchup. Formerly the acidity was
obtained from the fermentation of the tomatoes and the resultant acid
was probably mostly lactic. The flavor was different and not so
agreeable. A good cider, grain, or malt vinegar may be used. Most
manufacturers prefer to use grain vinegar of ten per cent acidity, as
the volume required is less and interferes less with concentration. For
real flavor, however, this may not be the best. Lately, glacial acetic
acid has been substituted for vinegar, a practice which can not be
approved and which ought to be abandoned. Citric acid is also added by
some. Vinegar is usually added near the finish of the batch, as
otherwise it attacks the kettle to some extent and a part is driven off
in boiling. Experiments made by adding vinegar to pulp and evaporating
to fifty per cent of its weight in twenty and forty minutes,
respectively, show that in the former case the added acidity was
decreased in almost the same proportion as the total evaporation, but in
the latter case the acid was not driven off quite so rapidly as the
moisture. This does not correspond with views held by chefs, as most of
them seem to believe that practically all the vinegar is driven off. In
order to obtain the sterilizing effect of boiling in an acid medium, it
is advisable to make this addition at least five to ten minutes before
the end of the cooking period. In home-made ketchup, vinegar is usually
added near, or at, the start, and aids in sterilizing the product, as
boiling alone may not, whereas, boiling in the presence of an acid will,

Oil is not an essential to ketchup, and while a small quantity is often
used to prevent foaming, its use in large quantities is undesirable.

Sugar is added to give the desired flavor. The higher the acidity,
whether natural, or acquired by adding vinegar, the greater the quantity
of sugar needed. In the high grades of ketchup, granulated sugar only is
used, but in the cheaper grades, soft sugar or glucose, may be used,
though the latter must be declared on the label. The sugar is usually
added when the cooking is about one-half completed. There is an
advantage in heating both the sugar and vinegar in a separate kettle and
adding them while hot, as it will prevent a check to the cooking and
lessen the sticking to the coils or kettle.

Salt is used in small quantity and is added near the close of the
cooking process.

The use of flour or starch in any quantity for the purpose of making the
body thick or heavy is properly regarded as an adulteration. This is
also true of pulp from a foreign source, like pumpkin or apples.

The density of the ketchup is left usually to the judgment of the chef,
who depends upon the appearance as it pours from the ladle. A quick test
can be made by weighing, as done for pulp, but in this case each
manufacturer must determine his own standard. A ketchup having specific
gravity of 1.090 is apt to be thin; a satisfactory consistency is
usually about 1.120 to 1.140.

As soon as the cooking is completed, the ketchup is run through a
finishing machine to remove all hard particles of tomato, bits of spice,
etc., and to give smoothness to the product by breaking it up into very
small particles. There are two types of finishers, the shaking sieves
and the rubbing machines. The former is suitable for thin ketchup. The
resultant product gives the best possible appearance under the
microscope, the tissue showing whole cells, little tearing, and the
minimum amount of debris and mold filaments. The objections to the sieve
are that the capacity is small and the waste is comparatively large. The
rubbing finisher needs to be very carefully adjusted, otherwise it
forces practically everything through in a very finely comminuted state.
The cells of the tissues are torn to shreds, their contents discharged,
molds are broken into hundreds of fragments, and a ketchup may be made
to have the appearance of being made from poor material. The finishers
have large capacity and will work on either light or heavy goods, but
like the cyclone, must be handled with judgment, not attempting to force
the last ounce through the sieve.


Only new bottles should be used and these should be thoroughly rinsed
before using and preferably with hot water. Since new bottles have no
tightly adherent particles on the inside, the use of clear water is
sufficient, dependence being placed upon the after process to insure

The bottling should be done at as high temperature as is practicable,
about 165 to 170 degrees F. If the temperature is higher than this, the
possibility of burns in handling is increased, and too much space is
left in the neck of the bottle after corking, due to shrinkage of the
ketchup on cooling, and if much lower, the expansion in processing
causes excessive loosening of caps or corks and breakage. Furthermore,
when low temperature is used, it requires a very long time to heat the
contents of a bottle in pasteurizing. A ketchup is a very poor conductor
of heat and the heavier the body, the longer the time that is required.

The closure may be made with either corks or seals, the recent
improvements in the latter making them much safer than they were a few
years ago.


After the bottles are sealed, they should be given a process to insure
sterility, the time being about fifty minutes for half-pints and an hour
and fifteen minutes for pints—or sufficient time to insure 190 degrees
F. for twenty minutes at the center of the bottle.

This step is omitted by many manufacturers, dependence for sterilization
being placed upon washing the bottle and subsequent heating for about
twenty minutes. The heating is accomplished by conveying the bottles
through a chamber containing numerous steam pipes at high temperature
and discharging them at the bottling machine. It is assumed that
sterilization of the ketchup has taken place in process of manufacture,
and the heat within the bottle will care for any infection which may
possibly have taken place at a later time from the cap or cork. The
safety of this measure depends upon using a fairly acid ketchup or one
with a heavy body. It is a risky procedure for mild or thin ketchup. It
is a common occurrence to have the stock keep apparently while in the
bottle, but spoil shortly after opening. The spoilage after opening is
most often due to forms which have been present since manufacture and
only need the presence of air to start growth, and are not due to
infection from the air. A ketchup will inhibit the growth of organisms
which gain entrance from without, while those which are present but held
in abeyance through exclusion of air, will sometimes grow. The writer
has samples of ketchup put up in 1906 which apparently are sterile, but
which will show spoilage within a few days after opening, though done
under sterile conditions, and the spoilage be identical in kind with
that observed soon after manufacture. How long these organisms will
remain alive is not known. In canning, no foods are considered safe
without processing, and the same principle is a good one to follow with

Processing may be accomplished in open tanks, in retorts, in specially
constructed pasteurizers, such as used in the brewing industry, and in
hot chambers, the method is not material, though there may be
considerable difference in point of economy.

                         FACTORY ARRANGEMENTS.

The making of ketchup is simple and the factory arrangement for doing
the work should be as compact as possible, so that after the pulp is
once heated, there is an advantage in having the various steps follow in
succession by gravity rather than be conveyed by pumps, especially in
small plants. The piping should be as short and direct as possible. The
machinery for filling bottles, corking, etc., leaves much to be desired;
as separate units they work fairly well, but there needs to be some
method devised for handling the bottles automatically from the time they
are placed on the washer until they are labeled, ready for the box. At
present the time between turning the crate of tomatoes upon the sorting
belt until it is ready for the box is only slightly over two hours.
Further improvement will not be so much in shortening the time as in
eliminating the hand labor.

The foregoing description applies to the making of unfermented,
non-preservative ketchup, made from sound stock and delivered into the
bottle. Very little ketchup, comparatively speaking, is sold to the
consumer in any package other than the bottle. It can be delivered into
the bottle when first made, at less expense for labor, with less fuel,
and with distinctly less waste than at any subsequent time. It will have
a better color and consistency than if stored in bulk and bottled later.
It is, therefore, advisable to bottle as much as possible at the time it
is made. Ketchup may be packed in bulk in jugs, tin cans, and in
barrels, but not satisfactorily; the jug is a poor package; the enamel
may be dissolved off the tin can and pinholes form; and the barrel
always gives a poor color and off flavor. The best container for bulk
ketchup is the gallon glass bottle.

                              PULP STOCK.

During the height of the season, it may not be possible to convert all
the tomatoes directly into ketchup, in which event the surplus may be
made into pulp. The first part of the operation is identical with that
already described. The concentration is carried just far enough so that
subsequently by slow heating for spicing it will give the proper
consistency when made into ketchup. A standard has not been fixed, but
tentatively it has been proposed that it be at about a specific gravity
of 1.035. The concentration may be carried further and water added at
the time of the final cooking, but when this is done, the resultant
product does not have the same smooth consistency that is obtained by
using the thinner pulp. Heavy pulp is made for the purpose of
economizing in cans, but experience has shown that economy does not
always follow. The higher the concentration, the higher the acid
content, and this may attack the enamel and metal with resulting bitter
flavor and frequent pinholes. Some manufacturers who prepare their own
pulp carry the concentration between 1.030 and 1.033. The method of
obtaining this density is to use flasks graduated to hold 500 or 1000
grams of water at 200 degrees F., fill them with the hot pulp and weigh
at once. For each flask there should be a proper counterpoise, and the
balance be sensitive and weigh in grams. If the 1000-gram flask be used,
the specific gravity will be the same as the weight of the pulp. With a
valve funnel the flask may be filled level full and the weight taken in
less than thirty seconds. For cold pulp, a similar flask is used, but
graduated at 60 degrees F. and after filling, the flask is set in a
sling and whirled a few times to free it from bubbles, filled again to
the level, and then weighed. For pulp of a specific gravity of less than
1.037, this gives fairly concordant results, but the errors increase
rapidly the higher the concentration. The same methods may be employed
on ketchup. Recently, W. D. Bigelow has improved the apparatus by using
a copper flask and adding a handle by which the flask may be submerged
in the kettle to take the sample and thus prevents the entrance of air.
The use of flasks of any size is described in Bulletin No. 3, National
Canners’ Association.

The use of the specific gravity method only partly solves the question
of standardization. Two pulps each of 1.035 may vary considerably in
what the chef terms body and there is no method of accurately measuring
this factor or expressing it. Pulp made by draining will be lighter in
weight with the same body, and that from skins and cores will be rough
or have the appearance of separating into small flakes or lumps. The
specific gravity bears a close relation to the soluble solids, and as
these do not have a constant ratio to the fiber in whole fruit, and as
the ratio is further disturbed by drainage and in the use of trimmings,
it is obvious that the method will not give an exact standard.

Pulp should be filled into gallon or five gallon cans as hot as possible
and sealed at once. The practice followed by some manufacturers is to
steam the cans first, then depend upon the heat in the pulp to
sterilize. The cans are allowed to stand hot for forty minutes, then
cooled. The other practice is to give the hot cans a process of about
twenty minutes for gallons, forty minutes for five gallons, and then to
cool. Cooling is essential to retain color and flavor, as prolonged heat
causes “stack burning,” producing a brownish color and a bitter taste.
The highest grade pulp can not be held in barrels for the reason that
the heat is retained too long. Stack burning will take place in glass if
the packages are not allowed to cool well in the air before being
stored, though the changes are not so marked as in the tin.

                          PULP FROM TRIMMINGS.

The losses in stock from canning tomatoes amounts to about forty per
cent. This is due to the unbusiness-like attempt to can all kinds—very
large, very small, and wrinkled, which can not be peeled with economy—to
wasteful methods of peeling, and to excessive draining of fruit from
handling in too thick layers. In this waste there is much that has good
food value and which might be worked up into pulp or ketchup stock if
properly done. In order to do this, the tomatoes should be sorted so
that only those which are in perfect condition for canning will go to
the peelers. These should be medium sized, firm, evenly ripened all
over, and free from wrinkles. Such tomatoes can be peeled at the minimum
of expense and loss. The sound tomatoes which are small, excessively
large, wrinkled, or with green butts, can go in with whole tomato stock.
The loss in peeling will then be small and can advantageously be
discarded. If it be decided to use trimmings from the peeling tables,
provision must be made for extra washing, as the ordinary washer removes
little more than the coarse dirt and particles, is not sufficient for
unusual conditions or to remove tightly-adhering material, and,
furthermore, rot must be eliminated before the tomatoes go to the
peelers. The writer has never seen a group of one hundred, or any
number, of peelers who will stop to trim and separate rot from peels and
cores. Trimming can be done better by a few when sorting the tomatoes
than at any subsequent step. If clean skins and cores can be had from
the peeling table, they can be converted into pulp and sold if labeled
properly, “from trimmings.” Whether such waste is suitable for a good
product depends upon how it is handled. For the most part, it has not
been handled as well as it should be.

The finished pulp made from skins and cores is not the same as that from
whole stock. It contains more fiber, remains more or less lumpy, and
lacks the smooth body of whole pulp. The color is not so good, and the
flavor is likely to be somewhat different. The flavor of the seed cells
and that of the fleshy portion of the tomato are different. Pulp made
from each part separately shows marked difference, that from the seed
cells being poor in color, but with the more characteristic fruit
flavor. Tests show that neither part has any true jellying powers, but
that the part from the seed cells gives the quality of smoothness, the
holding together of the particles of solids. Neither gives a first class
pulp alone.


Home-made ketchup generally has a rather dark reddish or brownish color,
due to prolonged heating, made necessary under kitchen conditions. At
one time this was thought desirable and some of the older recipes call
for the use of caramel in order to imitate this color. Most
manufacturers now aim to secure a clean, clear color, preferably bright
red. This may be obtained when good fruit is used and handled quickly; a
muddy brownish or yellowish color is looked upon with suspicion as
indicating poor material or defective methods.

The necessity for a clear red variety has already been pointed out, for
without proper stock, a superior product of uniform quality can not be
made. The tomatoes must be well vine-ripened, as the presence of green
fruit and green butts has a decidedly dulling effect. Colorimeter tests
show that the use of even small quantities of green material have an
immediate dulling effect. Promptness in handling the fruit after the
tissue is once exposed to the air is also essential. The tomato, like
some other fruits, turns brownish when the surface is cut or exposed.
This does not occur as rapidly, nor is it so marked as in apples or in
pears, but it is present. When the tomato is converted into pulp, every
particle is exposed to the air for a very short time—long enough to make
some slight change. The change is most marked in pulp from raw stock and
least in that which has been well heated. It naturally follows that
ketchup made promptly from whole stock will have the best color, that
from canned tomatoes next, then canned pulp, and lastly, that from
trimming stock. Pulp allowed to stand hot for too long a time will have
a brownish color like stack burning. When barrel pulp was used, this was
ascribed to the tannin extracted from the oak.

Pulp should not come in contact with iron at any stage, as the union of
the acid of the fruit with the metal will cause discoloration. When such
discoloration does occur, it becomes uniform throughout the mass, and
not in the neck of the bottle as has sometimes been described.

Darkening in the neck of the bottle is frequently due to the spices
used, as has already been pointed out. It can be redistributed
throughout the whole by placing the bottle in a shaker for a short time.

Darkening at the top may sometimes be due to extraction of color from
the corks. Soaking corks in two per cent acetic acid, then in hot water
before drying, and paraffining, will assist in preventing discoloration
on cheap grades.

Discoloration in the neck also results from the small amount of air
incorporated and from any subsequent addition which may come in through
the cork or seal. Bottles which are full to the cork may show no
darkening, those having a space of an inch or more between the contents
and cork may show little discoloration, while those having more space
will show much more marked discoloration. This holds for both pulp and
ketchup and in this case the discoloration begins on the surface and
works downward. The product made from some fruit will discolor more than
that made from fruit grown in another section of the country.

A bright red color is secured in some brands of ketchup by means of
paprika, as indicated under spicing.

A light colored ring in the bottom of a bottle is generally due to
organisms and debris, indicative of the use of barrel or trimming-stock
pulp, or it may result from changes after the process of manufacture. It
has been mistaken for sand.

                            KEEPING QUALITY.

Ketchup must not only keep while in the unopened bottle, but for a
reasonable time after opening, if it is to be a commercial success.
Every canner understands that if he puts food in a hermetically sealed
package and sterilizes by heat, that it will keep until opened. The same
principle applies to ketchup in the bottle, but there are some packers
who wish to be spared this expense and trouble and prefer to use a
substitute for heating.

The keeping quality after opening depends upon the utilization of the
same principles followed in the household operation of making fruit
butters, ketchup, preserves, and pickles, that is, sufficient
concentration and the use of sugar and vinegar. A ketchup can be made
essentially a pickle with an excessive quantity of vinegar and it will
keep; it can be made a preserve with excess of sugar and it will keep;
or, it can be made a distinctive sauce well concentrated in which the
vinegar and sugar are used only in sufficient quantity to give proper
flavor, and it will keep. Apple juice or cider will spoil quickly if
allowed to stand in a warm place; apple sauce will behave in like manner
only a little more slowly; but if the juice and sauces be boiled
together until they have acquired the consistency or state known as
apple butter, they will keep very well. The acidity, sugars, and solids
have been increased by the concentration. In the making of tomato
ketchup, the fruit does not have sufficient acidity and sugar of itself
to give preservative property at the concentration desired for a sauce,
so these are augmented by the addition of vinegar and sugar.

A great deal of stress has also been placed upon the effect of the
spices in acting as preservatives. Experiments have demonstrated
conclusively that when these are used in the small quantities required
for flavoring, that their effect is practically nil. The active
principles of the spices are effective only when present in the
proportion of 1 to 500 or 600 and in ketchup the proportion is only 1 to
several thousand. Likewise the quantity of salt is too small to have

The keeping qualities of a mild ketchup will depend far more upon the
sterilization than most manufacturers realize. It is easy to make almost
any ketchup apparently keep while the bottle is unopened. The spoilage
after opening is most often observed to be due to mold which has been
assumed to come from infection from the air. As a matter of fact, this
is nearly always due to spores which have been held in abeyance, due to
lack of air while in the bottle, and which begin growth as soon as
conditions are favorable. Spores which fall into the bottle from the air
might be unable to germinate upon such a medium, while those already
present would.


While tomato ketchup is a complex and variable product, its general
composition may be determined with a fair degree of accuracy. Inspection
will give a good idea of color, consistency, smoothness of body,
fineness of finish, tendency to separate, presence of objectionable
particles, and evidence of gross fermentation. The odor and taste will
give a clue to the kind and quantity of spices used and to a certain
extent the character of the raw material. Judging by odor and taste is
not so well done as judging by the eye by most persons. The education of
those two senses has been neglected and therefore fail to give all the
information which might be acquired in this way.

A chemical examination which will give the specific gravity, total and
soluble solids, sugar, salt, and total and volatile acidity, will be
sufficient to give a good idea of the stock used—tomato, salt, sugar,
and vinegar, but not the spices. A microscopic examination will assist
in determining the condition of the material used and whether
decomposition has taken place before or after manufacture. The facts
obtained through these sources will permit of classifying commercial
ketchup with a fair degree of accuracy.

There has been a very marked change in the character of ketchup since
the transition from the preservative to non-preservative goods, not only
microscopically, but also in composition. Formerly, there were very many
brands of thin liquid ketchup, showing little concentration of pulp,
very low in sugar, and having only small quantities of vinegar; the
standard was bulk rather than quality. The microscopic examination also
showed that the product had frequently undergone change before and after
preparation. Recent examinations show that there has been a very marked
improvement; that the body is decidedly heavier, more sugar and vinegar
are used, the tissue is cleaner, and there are fewer organisms present,
also that the difference in composition in preservative and
non-preservative ketchup is small, whereas, formerly it was marked.

The variations found in ketchup of rather recent examination show in the
non-preservative kind the specific gravity varied between 1.091 and
1.177; the solids between 19 and 37 per cent; the salt between 2 and 4
per cent; sugar between 12 and 29 per cent; and volatile acids between
.54 and 1.24 per cent. In the preservative kind, the specific gravity
ranged from 1.032 to 1.120; the solids from 9.23 to 28 per cent; salt,
1.48 to 3.4 per cent; sugar, 4.95 to 16.9 per cent; and volatile
acidity, .16 to .64 per cent. As a class they averaged lower in
concentration of tomato and in sugar and vinegar, though if proper
sterilization had been used, some of them would have kept without
difficulty. In experimental work it was found that a ketchup
concentrated so that when finished it showed an added sugar content of
15 per cent or more, a total acidity of 1.2 per cent, and a specific
gravity of 1.120 or more, that it would keep. To obtain a total acidity
of 1.2 per cent means the addition of about .4 to .6 per cent acidity in
the vinegar used. However, there are brands of ketchup on the market
which keep well after being opened and which have a total acidity of
less than 1.0 per cent.

The manufacturer can use the following as a starting point for
non-preservative ketchup; pulp, 100 gallons; sugar, 60 pounds; salt, 8
pounds; vinegar, 100 grain, 2 gallons; spice to flavor; and concentrate
to 50 to 55 gallons.


                        MICROSCOPIC EXAMINATION.

A discussion of the microscopic appearance of ketchup in terms which can
be readily understood by manufacturers is not an easy task, as it
necessarily involves technical knowledge. The subject has become one of
importance, owing to the attitude of many food officials in enforcing a
microscopic standard for this product, and on the part of many brokers
in requiring a guarantee to comply with this standard in making
purchases. Many manufacturers have either assumed or found it necessary
to have their finished products examined. Some employ “experts” to make
the examinations in their own plants, while the majority send their
samples to commercial laboratories. The total tax upon the industry for
such work amounts to thousands of dollars annually. The result of the
work as a whole has been beneficial, as any effort is which attracts
attention to details. It has likewise been the means of causing much
unpleasantness and not infrequently loss, because of lack of
understanding on the part of both manufacturer and examiner as to the
cause of certain findings. The manufacturers have proceeded in the usual
way without sufficient knowledge of what the resultant product will be
unless there is careful supervision of material and methods, while too
frequently the examiner is neither experienced in technique of the
examination nor in the effects of the different steps in manufacture
upon the product. Furthermore, much distrust in microscopic finding is
evinced when a half dozen or more samples from the same batch, sent to
as many persons, result in as many different reports. It naturally
causes a lack of confidence in both paid examiners and in food
officials, though those who make these examinations may be absolutely
honest in their findings. In order to clarify some of the points, it has
become necessary to go into detail, into both the method of examination
and into the effect produced by manufacture.

A scientific method of food examination is necessary for food officials
in order to determine the condition of a product, but is not necessary
for the manufacturer, though it may be advantageous. The latter is in a
position to know what enters his factory and what changes take place in
the food until it reaches the sealed package. He should have no fear of
a method which correlates the findings in the finished product with that
of the material used and the changes due to treatment.

Undue importance may seemingly be given to the subject of ketchup, but
the principle involved applies as well to other products.

The fundamental basis for the microscopic examination of any food
product must depend upon the structure of the material which enters into
its composition. Any attempt to determine an abnormal condition, such as
decomposition, without a knowledge of the normal, must necessarily be of
little value. There is some work which can be done in a mechanical
manner by almost anyone capable of looking through a microscope, and if
the work is properly supervised, it may have a value, but the lines
along which this can be done are very limited. Any attempt to apply such
superficial methods to the general examination of food products can not
properly protect the public and may be unfair to the producer. It has,
therefore, been deemed advisable to incorporate a brief statement
concerning the structure of the tomato before discussing the resultant


                        STRUCTURE OF THE TOMATO.

=Pericarp.= The tomato is a typical berry, the ovary wall, free from the
calyx, forming the fleshy pericarp, which encloses chambers filled with
a clear matrix, containing the seeds. The pericarp consists of an outer
tough membrane, the epidermis, a more or less thick layer of parenchyma
tissue, the pulp, and an inner thin, delicate membrane, the lining layer
of the loculi or chambers in which are the seeds. The epidermis consists
of a single layer of cells which have a very thick continuous cuticle
about one-half of the diameter of the whole cell. The cuticle differs in
chemical composition from the rest of the cell walls, being impervious
to water, and resisting rotting longer than do the cellulose walls. As
it is continuous over the whole of the fruit, the skin can be readily
separated from the other tissues. Hot water facilitates the removal of
the skin, as it causes the cellulose of the walls to swell more than the
cuticle, producing an effect as of shrinkage of the outer wall and a
consequent curling of the skin. The radial walls of the epidermis are
short and irregularly thickened, leaving pits in the walls, and giving
them a beaded appearance. The skin constitutes about 1.3 per cent of the

The layers of parenchyma just beneath the epidermis are closely united
and flattened, with their adjoining walls irregularly thickened. On
account of their position, they are called hypoderm. In the tomato the
hypoderm consists of two or three layers of cells, parts of which
usually separate with the epidermis. Below these cells are the
thin-walled parenchyma cells, which are approximately globular, vary
considerably in size, are very loosely held together, and have many
intercellular spaces. These cells constitute the mass of the pulp, and
with the juice constitute 96.2 per cent of the tomato.

The layer of cells which lines the chambers has the typical leaf
epidermal structure, the wavy outlines, the hollows and protuberances of
adjoining cells fitting one another so that they form a continuous
layer. They are also flattened laterally. The structure can be
understood readily when it is known that the pericarp is really a
metamorphosed leaf and that the outer side of the leaf forms the inner
wall of the ovary.

The chambers of the tomato are filled with a clear, slimy matrix in
which the seeds are embedded. The matrix consists of parenchyma cells of
various sizes and with delicate walls, and a small nucleus. The cells
are massed loosely, and can be separated readily. In those cells, as
well as in the wall cells, are starch grains which vary in size, being
round or approximately so, and having the hilum, when visible, a
straight line to one side of the center.

=Coloring Matters.= In the parenchyma cells are two coloring matters,
one yellow, which is amorphous in structure, and the other red and of
crystalline form. The sap contains a yellow color in solution which
differs in its reactions from those in the pulp.

=Red Color in Tomatoes.= The red coloring matter in tomatoes is in the
form of irregularly shaped crystal-like chromoplasts, which occur in
masses of various sizes. They are present in largest amounts usually in
the protoplasm which lies close to the ectoplasm and in that surrounding
the nucleus. They vary from sharp, bright-colored forms to those more or
less blunt in outline, and dull in color. They may be situated largely
in the periderm, the soft parenchyma beneath the periderm, or through
the whole mass of the parenchyma with the exception of the matrix
surrounding the seeds in the loculi. In tomatoes having the color in the
periderm a considerable amount is lost by adherence to the skin. The
chromoplasts are not affected by rotting to the same extent as are the
other constituents of the cell; they can be found floating free in the
debris from rotted cells, still retaining considerable color. They lose
their color gradually, in some varieties much more rapidly than in
others. In stored pulp which has fermented, the color may be faded to a
dull yellowish brown. In tomatoes intended for ketchup where a bright
red color is desirable, care should be used in the selection of a
variety having the chromoplasts bright, properly oriented, and in
sufficient quantity.

=Vascular Bundles.= In the pulp of the tomato are found strands of
vascular tissue, entering from the stem, and dividing and ramifying
through the soft pulp. These consist of long tubes with thin walls, some
of which have a strengthening band in spiral form on their interior
walls, the associated cells being without any special marking. The
strands vary in size from those having a few tubes to those having a
large number.

=Seeds.= The seeds of the tomato are small, flattened, yellow bodies
covered by a clear gelatinous membrane. Their peculiar characteristic is
the out-growth of hairs of varying lengths. The seeds constitute about
2.5 per cent of the weight of the tomato.

                         STRUCTURE OF KETCHUP.

Although the tomato pulp is broken into fine particles by the action of
the cyclone, and the skin and seeds are removed by the fine sieves,
pieces of the various tissues can be readily identified. The skin and
seeds have characteristics which would serve to distinguish them from
similar parts of other vegetables which might be used for adulteration,
but particles of skin and hairs from the seeds are rarely found. The
distinctive features which can be relied upon are the red,
irregularly-shaped, chromoplastic bodies in the parenchyma cells, and
the peculiar wavy-outlined cells of the lining layer of the chambers. As
nearly all young vegetable tissues have spiral vessels in their vascular
strands, these are not distinctive, except that they might differentiate
similar tissues of different size. There is very little starch in mature
tomatoes, and moreover, as the cooking causes the starch to swell and
lose its structure, the starch could not be used for identification.

Good ketchup made from whole tomatoes, in spite of the minuteness of the
particles, has a clean appearance, and can be readily distinguished from
poor ketchup. All ketchup will have some micro-organisms present, as it
is practically impossible to free the tomatoes from them in the washing,
but the number is very small in some of the best, in the manufacture of
which careful washing and sorting have been done. The poorer the
ketchup, usually, the greater number of organisms—bacteria, yeasts, and
molds; sometimes one form predominating, sometimes all three being in
great abundance, this latter condition usually prevailing in the poorest
ketchup, where more or less rotting has occurred.

As the tomato pulp is a favorable medium for certain organisms, these
will develop first, and it has also been determined that while one
organism is developing vigorously, others present are checked until the
activity of the first ceases. Then again, as the composition of the pulp
is being altered by the development of the organisms, the changes
induced render it a more suitable medium for other organisms which are
present but held in abeyance, so that pulp which has been allowed to
stand for some time will usually have present not only a large number,
but also different kinds of organisms.


When tissue is held and allowed to rot spontaneously, the pulp is
decomposed into a granular, watery mass. The cells beneath the epidermis
are the finest and driest in the sound tomato, considerable pressure of
the cover-glass being required to separate them for examination. Even
when forced apart, the cells retain their shape. They contain a delicate
semi-transparent protoplasm with a rather large nucleus surrounded by
protoplasm and having strands from this mass connect with the protoplasm
lining the wall. Pieces of the same tissue, on having the skin removed
so as to expose the broken tissue to the air, were covered with mold in
one day and in three days so badly disorganized that the cells separated
with the weight of the cover-glass. The cells were transparent, the
walls collapsed into a wrinkled mass, the protoplasm had disappeared,
except a skeleton of the nucleus, but the red chromoplastic masses were
intact. The middle lamella of the cells is the part which dissolves
first, allowing the cells to separate and causing the walls to become
thinner. The cell cavity is often filled with bacteria, so that the
effect of the rotting can not be seen until the cells have been washed
thoroughly. These bacteria have been mistaken for the particles left by
the decomposition of the cell contents. The vascular bundles are
surrounded usually by small parenchyma cells which do not separate
readily from the strand in the healthy tissue, but in the decayed tissue
the vessels can be seen clearly, free from other tissue. In advanced
stages of rottenness the walls of the vessels may be dissolved, leaving
only the spiral thickening, and the parenchyma tissue crumbled into
powder-like fragments. The parts of the tomato which resist rotting the
longest are the skin, which may be washed clean of adhering particles,
the spirals of the vessels, and red particles of the chromoplasts.

The conditions found in the rotted sections and pieces of tomato can be
distinguished in the poor ketchup and these factors, together with the
large number of organisms present, serve for purposes of

                         ORGANISMS IN KETCHUP.

Tomato pulp furnishes a medium suitable for the development of many
organisms, as it contains all of the necessary food elements. The raw
pulp has an acidity of from 0.2 to 0.4 per cent usually, though there
may be variation due to fermentation and other causes. On account of its
mild acidity, it is especially suitable for the development of many
yeasts and molds, and some forms of bacteria, consequently there is
present a varied and abundant flora if the pulp be held for an
appreciable time before using, or if it has been made from tomatoes not
properly sorted and washed. Where the black rot occurs on tomatoes, the
tissue is hardened like cork, and if not removed on the sorting belt, is
broken into small pieces by the cyclone, and appears as black specks in
the ketchup, these being readily perceived by the naked eye. The white
rot forms soft spots, which, though not so prominent as the black, carry
much more contamination, as, apart from the bacteria, yeasts, and molds
present, they are often swarming with Protozoa. These are not ordinarily
recognized in the ketchup, as a chemical or physical shock causes them
to contract, assume a spherical shape, and become motionless. In this
condition they resemble the immature conidia of some of the molds.
Rarely only one organism predominates in pulp from rotted fruit, then
the rot consisting of a nearly pure culture. In all cases of soft rot,
there is much more contamination carried, as the organisms are small and
a greater number present in a given area. Whenever the inner tissue of
tomatoes is exposed, organisms develop rapidly, the forms varying with
the locality and the conditions in the pulp. Some of these organisms may
survive the treatment of the pulp when converted into ketchup, or the
original organisms may be destroyed, and a different set gain access and
develop, but in either event all the organisms alive or dead which were
present at the period of manufacture are found in the ketchup. It has
been noted that certain brands of ketchup have predominating organisms
present which are practically constant from year to year.

A method for the microscopic examination of ketchup in order to
determine the number of organisms present is described in Circular No.
68, Bureau of Chemistry. It consists in an adaptation of a method used
in examining blood in physiological and pathological work, and of yeast
in the brewing, wine-making, and distilling industries. The outfit
required consists of two parts, the microscope and the counting chamber,
each with minor accessories. The optical outfit recommended for food
examination consists of a microscope with eye pieces and objectives
which will give approximate magnifications of 90, 180, and 500
diameters. It is advised that these magnifications be obtained by using
16 mm and 8 mm apochromatic objectives, and ×6 and ×18 compensating
oculars (×6 ocular and 16 mm objective equals ×90; ×6 ocular and 8 mm
objective equals ×180; and ×18 ocular and 8 mm objective equals ×500),
higher objectives being impracticable on account of their short working
distances. This equipment is adequate for working upon blood or yeast,
but is wholly inadequate for bacteriological work, except that of the
simplest character and under conditions quite different from those found
in ketchup and other food products.

The counting apparatus or chamber recommended is known as the
Thoma-Zeiss haemacytometer, named from the designer and maker. The
apparatus consists of a heavy glass slip, on which is cemented a glass
0.2 mm thick, having a circular hole in the middle. In the center of the
hole is mounted a smaller disk 0.1 mm thick, leaving an annular space.
In the middle of the small inner disk are etched two sets of twenty-one
parallel lines which cut each other at right angles. The drop of liquid
to be examined is placed on this square, after which it is covered with
a specially heavy cover-glass, which, if perfect and adjusted so closely
that Newton’s rings appear, gives a layer of liquid 0.1 mm in depth. The
drop to be examined must be so small that it remains in the middle of
the chamber, but in contact with the cover-glass and bottom of the cell.
Each side of the ruled square is 0.1 mm, and as there are 20 spaces on a
side, there is a total of 400 small squares, the depth being 0.1 mm,
thus the cubical content of each is 1-4,000 c mm or 1-4,000,000 cc. For
convenience in counting, every fifth space is sub-divided. Other
counting chambers have been devised based on the same principle, but
varying chiefly in their rulings for convenience in counting.

The other apparatus recommended consists of a 50 cc graduated cylinder,
slides, and cover-glasses.

Since the counting chamber has been used extensively in blood
examination and in yeast work, a brief description of the technique as
followed in the latter may serve to give a better understanding of its
limitations. First, in the preparation of the sample, the cylinder and
flasks for mixing, and the pipette must be absolutely clean. The liquid
to be examined is shaken thoroughly and then the measured sample
withdrawn as quickly as possible to prevent the cells from settling and
diluted with weak sulphuric acid (about 10 per cent), which prevents any
further development of cells, and also aids both in the separation of
the cells from one another and in their suspension—the latter factor
being important when only a single drop is taken for examination. When
counting blood cells, a normal or other salt solution is used so as to
have the specific gravity of the diluent approximately that of the blood
serum. The dilution is made as low as possible, since the number
obtained in the count has to be multiplied by the dilution co-efficient,
and any errors made are increased proportionately. A slight error when
multiplied by the factor 4,000,000, the unit for each square, becomes
very large in the total. The sample is shaken very thoroughly after the
diluent is added, a drop of the liquid taken by means of a pipette,
placed in the center of the counting chamber, and the cover-glass put in
place. The withdrawal of the pipette and the transference of the drop to
the chamber are done as quickly as possible to prevent the cells from
sinking. The determination of the number of blood corpuscles, yeasts, or
other cells in one cubic centimeter, the unit of volume generally used,
will depend upon the average found in a number of squares. The number of
squares to be counted is determined by making counts until a constant
average is obtained, for if a true average is not obtained, the
counting, naturally, is of no value. If the mounts do not show
uniformity in the field, they are repeated.

In using the counting chamber for counting yeast cells and blood
corpuscles, for which it was originally devised, the bodies to be
examined are fairly large, well defined, and suspended in a fairly clear
liquid, usually of rather high specific gravity. Even with these
favorable conditions, the work must be done by observing the most
careful technique in order to get relative results, which will be of
value, and they are absolutely useless if any detail has been slighted
or neglected. In attempting to adapt the method to food products, very
different conditions are encountered—conditions which are opposed to
obtaining accurate results. Food products, like ketchup, consist of a
mixture of solids and liquids in which are various forms of organisms,
the latter in varying condition, due to their environment and treatment,
as well as to stages of disorganization.

In estimating the number of yeasts and spores in pulp or ketchup, the
Thoma-Zeiss counting chamber is used and the mount observed under a
magnification of 180 diameters. To prepare the sample, 10 cc of the
material has 20 cc of water added and is “thoroughly mixed.” Before
taking a drop for examination, the sample is allowed to rest for a
“moment” to allow the “coarsest particles” to settle. This step in the
technique is not as clear as could be desired, for what might be
considered as “thoroughly mixed” by one microscopist as a half dozen
shakings of the cylinder, might not be so construed by another even with
sixty shakings. As the material consists of both solids and liquid, this
is a very important detail, as it may easily account for some of the
wide differences in results obtained by different workers on the same
sample. In a bulletin[2] dealing with the examination of solid foods,
the following statement occurs relative to the shaking in order to be
able to obtain the bacterial condition: “The longer the shaking, the
more perfect was the diffusion of particles. It could not, however, be
continued beyond a comparatively short period of time, because of the
multiplication of organisms. With the quantities of tissue above stated,
ten minutes’ shaking was selected as a happy medium between an
undesirable multiplication of the organisms on the one hand and the
retention of the organisms by the tissue and the consequent lowering of
the numbers found, on the other.” The organisms in pulp or ketchup are
dead, or, if alive, do not possess such phenomenal power of
multiplication, therefore, the shaking should be conducted with
sufficient energy and for a sufficient time to insure their separation
from the tissue. Furthermore, “letting stand for a moment” may mean
thirty seconds or two or three minutes to different persons.


Footnote 2:

  No. 115—Bureau of Chemistry, Dept. of Agr.

In all biological work involving the counting of organisms, either by
the plate or direct method, in the case of yeast, the operator works as
rapidly as possible to prevent the organisms from settling, so as to
have them evenly distributed in order that he may obtain an average
sample. A pipette is used for removal of a drop of the liquid and the
drop placed in the chamber as quickly as possible to prevent settling.
No directions are given as to how the drop of the diluted pulp or
ketchup is to be removed to the chamber, so that a stirring rod or other
apparatus is frequently used, as the solid particles interfere with the
use of a fine pipette. If the rod be inserted to the bottom, or nearly
to the bottom of the mixture and withdrawn slowly and another withdrawn
somewhat rapidly, a difference of fifty per cent or even more may result
in the count. It is not possible for different operators to use
pipettes, glass rods, pen knives, toothpicks, and matches for drawing
the samples, and get comparable results. It has been found that in (all
of these have been seen in use) the counting of the organisms in pulp
and ketchup, some persons use distilled water, others tap water, some
clean their measuring flasks and pipettes, while others rinse them, so
that naturally reports are made of such varying numbers that
manufacturers do not look upon the method with confidence. It is only by
using uniform methods and the same care necessary for other biological
work that even an approximation can be made.

                        STRUCTURE OF THE TOMATO.

To obtain the number of yeasts and spores in the sample, a count is made
in one-half of the ruled squares. Two hundred squares represent a volume
equivalent to 1-20 c mm, which, multiplied by the dilution, would give
the number in 1-60 c mm. It is stated that it is believed that it is
possible for manufacturers to keep the count below 25 per 1-60 c mm.

The same mount is used in estimating the bacteria, but the ×18 ocular
used so as to increase the magnification to approximately 500 diameters.
The “number in several areas, each consisting of five of the small
squares, is counted.” Nothing is said as to the order of the five
squares, whether in a row or other arrangement, nor what number
constitutes “several.” The average number found in five squares
represents the number in 1-800,000 part of a cc, and this multiplied by
3, for the dilution, would make the factor 1-2,400,000 for a cc. It is
stated that it is believed that it is possible for manufacturers to keep
within 12,500,000 bacteria per cc in the pulp and 25,000,000 in ketchup.
The number present is expressed in terms per cc though the yeast and
spores are expressed in 1-60 c mm. Possibly bacteria to the lay mind
mean something dangerous, so by expressing the numbers in millions they
appear appalling. Yeasts and spores are not so generally associated with
dirt and disease so that by giving them a small unit, only 1-60,000 part
of a cc, they may seem much less offensive. If the mind is capable of
conceiving what is meant by millions per cc for bacteria in one case,
there seems to be no good reason why the same unit of volume should not
hold for the other.

To estimate the number of molds present, a drop of the undiluted pulp or
ketchup is placed on an ordinary slide and the ordinary cover-glass
pressed down until a film of 0.1 mm is obtained. The directions state
that after some experience this can be done, but do not state how one’s
efforts may be directed to obtain this result. It is apparent that by
experience in comparing a measured amount with a judged amount that the
tendency would be toward accuracy, but in this case there is no measured
amount for comparison, except the diluted drop in the counting chamber.
Some workers have placed thin cover-glasses under the edges of the mount
so as to have something to help in estimating the thickness of the film,
but as the thinnest ordinary cover-glasses vary from .12 to .17 mm in
thickness, the error varies 20 to 70 per cent from that required. One
manufacturer in advertising No. 1 cover-glasses states that they vary
from 0.13 to 0.17 mm, while another states they vary from 1-200 to 1-150
of an inch (0.127 to 0.169 mm). Careful checks show that it is not
always easy to get exactly .1 mm on the specially prepared counting
chamber; that unless the cover be placed with care and pressed uniformly
on all sides until Newton’s rings appear, a variation of ten per cent or
more in thickness may occur, and without such a guide the error becomes
greater. The micrometer screw adjustment on the microscope can be used
to help in determining the thickness, but none of the workers observed
has used this refinement.

The examination for mold is made with the ×6 ocular and 16 mm objective,
giving a magnification of approximately 90 times. About 50 fields are
supposed to be examined and the result expressed in terms of the per
cent in which mold was found. It is stated that it is believed that
manufacturers can conduct their operations so that mold will not be
present in more than 25 per cent of the fields. There are, therefore,
three units in which to express the results: bacteria in cubic
centimeters, yeasts and spores in one-sixtieth of a cubic millimeter,
and molds in percentage of microscopic fields.

Aside from the errors which may occur in the manipulation of the purely
mechanical part of the technique, there are other considerations which
affect the accuracy of the results. First, the differentiation between
organisms and tissues is not considered possible by most pathologists
and bacteriologists without differential staining. Even in such simple
examinations as those for diphtheria and tuberculosis, a stain is
required. In foods the particles of the plant tissue and the organisms
are not so different that they can be clearly separated without using
similar technique. It is possible to make some separation, but not with
accuracy. Threads of protoplasm may be mistaken for bacilli; the
granular contents of a cell for cocci, yeasts, or spores; bits of cell
wall for hyphae under the magnifications given, and the results obtained
be high or low, depending upon the personal ability of the operator.
Each error magnified by the enormous factor used in calculating the
final result naturally gives figures which may be far above or below the
truth. Those who have had special training in plant structure and
bacteriology are likely to give the higher figures, while those who have
had these subjects as incidentals in a scientific course are apt to give
much lower ones.

Second. The standard is set for what organisms shall be counted and
those which need not be. It is said that micrococci need not be counted
because of the difficulty in distinguishing them from “particles of
clay, etc.,” and not upon their power to produce decomposition. When an
organism is a coccus and when rod shaped is not easily settled, even
with the aid of pure cultures and high power objectives. More than one
organism has found a home first in one group and then in the other, and
differentiation with the low power obtained by an 8 mm objective is
impossible. There are always present some very large rods, but there may
be more very short ones which may not be counted, and there is nearly
always a diplococcus present, which, with the magnification used, is
difficult to differentiate from a rod. There are four forms associated
with rot and tomato diseases which have been carefully studied—all rods,
but very small ones. Ps. fluorescence, 0.68×1.17-1.86; Ps. michiganense,
0.35-0.4×0.8-1.0; B. carotovorus, 0.7-1.0×1.5-5; and B. solanacearum,
0.5×1.5. Bacillus subtilis, .7×2-8 and some lactic acid forming
varieties are always present. It is clearly a matter of judgment on the
part of the examiner as to which organisms he will count and which he
will not attempt to count. A personal equation is thus introduced which
nullifies the possibilities of scientific accuracy.

The yeasts and spores are counted together. They can not be separated
under the microscope, neither can they be differentiated from contracted
protozoa which may be present in large numbers. In counting these, it is
not always possible to distinguish the smaller yeast cells and smaller
spores from the refractive bodies which are formed in some mold hyphae
when these are impoverished, and which are liberated if thorough shaking
of the sample be done. The yeasts found in pulp and ketchup are more
likely to be “wild yeasts” and these are, as a general thing, smaller
than the cultivated, sporulate more readily, and have more highly
refractive spores. Then, some of the so-called molds found form minute
conidia and when these and the yeasts are mixed with the detritus of the
tomato and the mass subjected to heat, with the consequent changes, the
accuracy of the count becomes a somewhat problematical matter. A careful
examination of the kind and condition of the hyphae present might assist
materially in making some distinction.

In counting molds, no distinction is made as to whether a small bit is
in the field or a large mass. In making a mount for molds, the solids
generally tend to stay in the center of the field while the liquid tends
to run to the edge. The fields selected may therefore give a high or low
result determined by their location. One examiner desiring to favor the
manufacturer may select the outer part for most of the fields, while
another, making the examination for the buyer, who may wish to make a
rejection, may reverse the operation. Some persons modify the directions
given by counting only pieces which are one-sixth the diameter of the
field, while others use a smaller fraction. It is easily possible to
have one clump of mold in one field which will be twenty to thirty times
in extent that of another, yet both are given equal value in the final

Third. No real relation exists between the organisms counted and
decomposition, for mere numbers are not always coincident with
putrefactive activity. A pulp or ketchup may be bad and show less than
30,000,000 bacteria, or it may be good and show 300,000,000. Rotting, or
decomposition, may depend more upon the cocci and the organisms which
are not counted than upon those which are. The only work done in which
microscopical and chemical work were reported on the same samples
appears in Circular No. 78, Bureau of Chemistry. This was not done upon
samples prepared and kept under control, but for the most part upon
commercial pulp and ketchup. The results do not show any close relation
between the number of organisms and the lactic acid content which is
given as the measure of decomposition.

Fourth. Bacteria are expressed in numbers per cc, yeast and spores in
numbers per 1-60 c mm. Since the counting can be done only in the fluid
portion, an error occurs proportional to the number of bacteria in or
attached to the tissue which cannot be counted.

The error of assuming that numbers of organisms alone are a sufficient
index of the wholesomeness of a food product is well illustrated by work
on water analysis. The following statement by an authority on the
subject is illuminative: “The belief is widespread among the general
public that the sanitary character of a water can be estimated pretty
directly by the number of bacteria it contains. Taken by itself,
however, it must be admitted that the number of colonies which develop
when a given sample of water is plated affords no sure basis for judging
its potability. A pure spring water containing at the outset less than
100 bacteria per cubic centimeter may come to contain tens of thousands
per cubic centimeter within twenty-four to forty-eight hours, after
standing in a clean glass flask at a fairly low temperature. There is no
reason for supposing that the wholesomeness of the water has been
impaired in any degree by this multiplication of bacteria.”[3]


Footnote 3:

  Jordan, E. O. A text-book of General Bacteriology. 1908.

There are certain steps in the process of manufacture which also
influence the number of organisms which may be counted. A pulp may vary
from an unevaporated tomato juice to a concentration which is
represented by an evaporation of a volume of water up to 60 per cent,
and ketchup may vary from a thin watery consistency to one which is so
heavy that it will scarcely flow from the bottle. It becomes evident
that a method which does not sustain some close relation to the amount
of tomato present would naturally be deficient as a standard for
judging. For example, a tomato juice with an initial count of 10,000,000
if evaporated to one-half its volume will have more than twice the
number of organisms estimated in the original. The pulp is composed of
both liquid and solids and part of the liquid portion only is driven off
by evaporation, leaving in the residue a different proportion to the
solids. As the organisms can be counted only in the liquid portion, it
is obvious that with concentration, the number will be increased at a
much greater ratio than will the reduction of the bulk. A thin pulp with
10,000,000 bacteria may easily be worse than a heavier one with
30,000,000 or 40,000,000, if judged by numbers alone. The same
conclusion is necessarily true for ketchup. It clearly refutes the
argument that a product having twice as many bacteria as another of the
same kind is more than twice as bad. The effect of recommending an
arbitrary low limit for bacterial content, irrespective of the
consistency of the product, is to cause manufacturers to pack thin pulp
and sloppy ketchup, and to discourage the more desirable heavy body. The
examination of a very large number of samples shows that the majority of
the heavy pulps and ketchup upon the market show much higher counts than
the thin ones when the tissues show good stock in both.

It is not possible to concentrate any pulp to the consistency of paste
and have it pass under the present method; that is, considering a
product to be filthy, putrid or decomposed if the bacteria exceed
25,000,000 per cubic centimeter.

There are some soup and ketchup manufacturers who still follow the
draining method for separation and this is generally done to secure a
certain quality in the flavor. This kind of pulp always shows a high
bacterial count, which is usually ascribed to fermentation. As the
draining can be started in about twenty minutes, and is nearly always
completed in forty minutes to one hour, there is little time for
fermentation, and yet such a pulp may show several times the count of
the original whole pulp. The condition is similar to that which takes
place in the separation of cream by gravity. Dr. John F. Anderson, U. S.
Public Health Service,[4] has shown that the bacterial content of
gravity cream is about sixteen times that of bottom milk and that this
discrepancy may be much wider. One test is given in which the cream
showed 386 times as many organisms as the bottom milk. The question
logically arises whether, if a pulp which contains 10,000,000 bacteria
per cubic centimeter and is considered sound, becomes “filthy, putrid or
decomposed” when the same pulp is heavily concentrated and the count
becomes 100,000,000, or a cream is bad when it contains 2,000,000,
though the whole milk from which it was derived contained only 300,000.
There should be a recognized difference in rating a product in which the
number of organisms is influenced by concentration, and one in which
they have developed. Some very erroneous statements have been made upon
increase of bacteria in pulp while standing. Some of these have been
based upon the academic proposition that reproduction in bacteria may
occur every twenty minutes under perfect conditions of food supply,
freedom of movement, and optimum temperature. Such statements are
obviously not based on experiments with pulp. Assuming that such a rate
of reproduction were possible, a pulp with an initial start of only
5,000,000 would increase to 10,000,000 in twenty minutes; 20,000,000 in
forty minutes; 40,000,000 in one hour; 80,000,000 in one hour and twenty
minutes; 160,000,000 in one hour and forty minutes; 320,000,000 in two
hours; and 2,560,000,000 in three hours. No food product like tomato
pulp, cider, or grape juice would be usable in a very short time. To
determine the rate of increase of the organisms in tomato pulp,
experiments were made, using sound tomatoes. In each experiment, the
tomatoes were divided into two lots, one lot used raw, the other
steamed, the steaming varying from two minutes’ time, just sufficient to
slip the skins, and eight minutes, in which the whole tomato is
softened. Samples were taken at hourly intervals for the first six
hours, then at intervals of twelve hours, the samples counted by means
of the plate and direct methods. For the plates tomato gelatin was used
with an acidity of 0.3% and 0.4%, the samples for the direct count were
put in cans, sterilized, and counted later. With the lower acidity there
were liquifiers which prevented the counting of some plates, so that in
the later trials the higher acidity gelatin was used. The count of the
molds was not normal, due to the frequent stirrings, which prevented
spore formation, besides injuring the hyphae.


Footnote 4:

  The Journal of Infectious Diseases. 1909. Vol. 6, p. 393.

The results varied, some pulps giving a much higher initial count than
others, but they all agreed in having a comparatively slight increase in
the first three hours, the large numbers which one is led to expect not
being present until the pulp had stood for at least five hours and under
the most favorable conditions; usually it requires a longer time. The
plates and the direct count agreeing in the general trend, though the
numbers obtained by the two methods varied. In the pulp obtained from
the steamed tomatoes, the initial count was much lower in the tomatoes
steamed eight minutes, being only 20 per cc in the plates, but the same
thing was true of these in that the increase was very slow at first. The
figures from all the trials, both raw and steamed pulp, and from the
plates and direct counts, show that the theoretical estimation of the
increase of organisms from the classic twenty minutes required for
reproduction of an organism with the consequent progression,
irrespective of the condition of the organism at the start, or its
environment, will have to be modified. In the plates all colonies, aside
from the molds, were counted as bacteria, but this would not give a very
large error, as yeast does not reproduce at the same rate as do

The state of comminution of the product determines to a considerable
extent the number of organisms which may be counted. The more finely the
comminution, the greater the number. Two pulps made from the same
material, one run through an ordinary cyclone and the other through a
finishing machine, will show from 50 to 100 per cent more in the latter.
Coarse pulp and coarse ketchup may be inferior articles and yet give the
better results by the direct method. The effect on the mold is even more
marked—filaments and clumps will be torn into many small particles. The
total quantity is not increased, but it is distributed more nearly
perfectly and thus occurs in more fields.

In work done on meat to determine the technique which should be employed
in the bacteriological analysis, comparison was made between shaking the
sample and grinding it in a mortar with sand. In the three samples
reported, the shaking gave only 3, 12, and 13 per cent, respectively, of
those obtained from grinding.[5]


Footnote 5:

  Weinzirl, John and Newton, E. B. American Journal of Public Health.
  Vol. IV, No. 5.

A finely comminuted pulp was vigorously shaken for definite times and
samples taken as quickly as possible after the tenth, fiftieth, one
hundredth, and two hundredth times shaken. The results were as follows:

                                             Yeast and   in Per
                No. Times       Bacteria    Spores Per  Cent of
         No.      Shaken.       Per c.c.     1-60 c.c.  Fields.
         1             10     31,020,000            22       80
         2             50     50,040,000            42       76
         3            100     84,730,000           106       92
         4            200    116,640,000           116      100

In line with this are the results obtained before and after shipping
long distances. When the goods have been handled roughly during shipping
the count is much higher.

The length of time elapsing after manufacture until the counting is done
also has an effect. Pulp put up in the fall will show one count and the
same pulp the following season a different count. This difference is not
due to any multiplication during storage, but to the fact that the
organisms separate from the tissues more readily. The difference made in
the counting from this treatment is not as marked as that produced by
the other factors already treated, but is sufficient to cause a change
in the count.

It is known that the surface of plants is covered by a variety of
bacteria and other fungi that remain dormant under unfavorable
conditions, but that these become active when the food which is
invariably present is rendered available by access of moisture, either
dew or rain, or the rupture of the host, etc. These will vary in numbers
with the season, wet or dry, hot or cold, in different sections of the
country, and, in the case of the tomato, with the variety of the fruit;
whether perfectly smooth or with a slight bloom; whether irregular or
regular in shape; and whether slightly green with a firm skin or fully
ripe. These are all factors that have an influence and should not be
overlooked. Some packers have already learned that by packing tomatoes
which are colored, but not really ripe, that the count will be lower,
and as such a practice extends, it means the use of poorer material
instead of that which is properly developed and with the normal flavor.


 ● Transcriber’s Notes:
    ○ Typographical errors were silently corrected.
    ○ Inconsistent spelling and hyphenation were made consistent only
      when a predominant form was found in this book.
    ○ Text in bold is enclosed by “equal” signs (=bold=).

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