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                        Issued January 9, 1909.

                   U. S. DEPARTMENT OF AGRICULTURE,
                BUREAU OF CHEMISTRY--BULLETIN No. 119.
                     H. W. WILEY, Chief of Bureau.

                      EXPERIMENTS ON THE SPOILAGE
                          OF TOMATO KETCHUP.

                                  BY
                            A. W. BITTING,
                    INSPECTOR, BUREAU OF CHEMISTRY.

 [Illustration: Shield of the United States Department of Agriculture]

                              WASHINGTON:
                      GOVERNMENT PRINTING OFFICE.
                                 1909.




LETTER OF TRANSMITTAL.


                   U. S. Department of Agriculture,
                         Bureau of Chemistry,
                  _Washington, D. C., July 15, 1908_.

Sir: I have the honor to submit for your approval a report made by
Inspector Bitting of experimental work on the spoilage of tomato
ketchup, the conditions contributing thereto, methods of prevention,
the action of preservatives, and the length of time that the product
will keep under varying conditions of manufacture and temperature, both
before and after opening. Every effort has been made to conduct the
work in a practical way, and the results obtained can not fail to be of
interest and profit both to the manufacturer and consumer. I recommend
that this report be published as Bulletin No. 119 of the Bureau of
Chemistry.

  Respectfully,                H. W. Wiley,
                                   _Chief_.

Hon. James Wilson,
    _Secretary of Agriculture_.




CONTENTS.


                                                              Page.

Introduction                                                      7

Process of manufacture                                            8
    Selection and preparation of stock                            9
    Pulping                                                       9
    Cooking and seasoning                                        10
    Evaporation and finishing                                    11
    Bottling                                                     11
    Processing                                                   11

Character of products                                            12
    First-class products                                         12
    Inferior products from “trimming stock”                      13

Labels                                                           14

Manufacturing experiments without the use of preservatives       15
    Outline of experiments                                       15
    Discussion of results                                        17
        Spoilage of ketchup after opening                        17
        Spoilage of unopened ketchup                             20
        Spoilage of market brands                                20
        Sterility of ketchup                                     21

Experiments with preservatives                                   22
    Sodium benzoate                                              22
    Salt                                                         23
    Sugar                                                        23
    Spices                                                       24
        Water infusions                                          24
        Acetic acid extracts                                     25
        Oil extracts                                             25
    Vinegar and acetic acid                                      26
    Oil                                                          27

Study of Penicillium in ketchup                                  28
    Development                                                  29
    Reproduction                                                 29
    Growth in ketchup                                            30
    Temperature tests                                            31

Histological structure of ketchup                                33

Microscopical examination of some commercial brands              34

Summary                                                          35




ILLUSTRATIONS.


PLATES.

                                                              Page.
PLATE I. Penicillium. Fig. 1.--Conidia, normal growth
     and in various stages of germination, some with branching
     hyphæ. Fig. 2.--Conidiophore, showing unusually large
     development of conidia; from culture in moist chamber       28

     II. Cultures from ketchup preserved with sodium
     benzoate. Fig. 1.--Conidia and hyphæ from culture in
     experimental ketchup containing one-sixteenth of 1 per cent
     of sodium benzoate. Fig. 2.--Conidia and hyphæ from culture
     in experimental ketchup containing one-tenth of 1 per cent
     of sodium benzoate                                          28


TEXT FIGURES.

Fig. 1. A model receiving platform                                8

2. Large receiving room showing the sorting belt                  9

3. A section of a kitchen showing the copper cookers             10

4. An example of factory practice                                12

5. Another factory interior                                      14




EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP.




INTRODUCTION.


The tomato, _Lycopersicum esculentum_, is supposed to be native to
South or Central America. The large fruits commonly used grow only
under cultivation, but the variety with small, spherical fruits,
known as _L. cerasiforme_, has been found on the shore of Peru and is
considered by De Candolle[A] as belonging to the same species as _L.
esculentum_. Though grown extensively in Europe, there is nothing to
indicate that it was known there before the discovery of America. The
tomato was introduced into China and Japan at a comparatively recent
date. De Candolle is of the opinion that the tomato was taken to
Europe by the Spaniards from Peru and was later introduced into the
United States by Europeans. Tomatoes were brought to Salem, Mass., by
an Italian painter in 1802,[B] who is said to have had difficulty in
convincing the people that they were edible. They were used in New
Orleans in 1812, though as late as 1835 they were sold by the dozen in
Boston. After 1840 they came into general use in the Eastern States,
but it was later than this before tomatoes were used freely in the
Western States, many persons having the impression that, since they
belonged to the nightshade family, they must be unwholesome. The extent
to which tomatoes are used at the present time shows how completely
this prejudice has been overcome.

[A] Origin of Cultivated Plants, 1890.

[B] Webber, H. J., Yearbook, U. S. Department of Agriculture, 1899.

The name _Lycopersicum_ is from two Greek words, meaning a wolf, and
a peach, the application of these terms not being apparent; the name
of the species, _esculentum_, is from the Latin, meaning eatable.
The common name “tomato” is of South or Central American origin, and
is believed to be the term used in an ancient American dialect to
designate the plant,[C] but its meaning is unknown. The English call
the tomato “love apple,” which in French is “pomme d’amour.”

[C] U. S. Dept. Agr., Exper. Sta. Record, 1899-1900, 11: 250.

The tomato is considered a typical berry, the ovary wall, free from the
calyx, forming the fleshy pericarp, which incloses chambers filled with
a clear matrix containing the seeds. The fruit measures from 1 to 5
inches in diameter, and is red, pink, or yellow when mature.

The plant sports freely, producing many varieties, which differ mainly
in the size, shape, and quality of the fruit. The varieties bearing
small fruits are _L. cerasiforme_ and _L. pyriforme_, each bearing a
two-celled fruit, the former being round, and somewhat larger than
a cherry, and the latter pear-shaped. These small tomatoes are used
ordinarily for preserves and pickles.

The word “ketchup” is adopted in this bulletin as the form which ought
to be given preference. The derivation of the term is not definitely
known. The spelling “catchup” given in some of the leading dictionaries
appears to be based on the erroneous idea that the first syllable
“ketch” is a colloquial form of “catch.” Several authorities derive the
word from the East Indian or Malayan “kitjap,” because “ketchup” was
originally a kind of East Indian pickles. Some give the word a Chinese
origin, while others assert that it comes from the Japanese. A majority
of the manufacturers employ the word “catsup,” a spelling for which
there does not appear to be any warrant.


PROCESS OF MANUFACTURE.

[Illustration: Fig. 1.--A model receiving platform.]

The making of tomato ketchup consists essentially in reducing tomatoes
to pulp, removing the skins, seeds, hard parts, and stems, adding
salt, sugar, condiments, and vinegar to suit the taste, and cooking
to a proper consistency. The methods and practices of the various
manufacturers differ, and the difference between the best and the
poorest procedure corresponds to that between the best and the worst
ketchup. No single factory has all of the best methods at every step
of manufacture. Some perform certain details well and are negligent
in others. In some, large amounts of money are spent on equipment to
improve a particular point considered advantageous by the trade, while
other details essential to the making of a good-keeping ketchup are
disregarded. A statement of the best practice as observed at a number
of factories, together with some facts obtained from experiments, will
be given.


SELECTION AND PREPARATION OF STOCK.

The tomatoes should be home-grown, of a red variety having the minimum
of yellow and purple color, be picked when ripe, and delivered to
the factory promptly without mashing. All tomatoes should pass over
an inspection table, the rotten and otherwise unfit fruit should be
discarded, and the green tomatoes should be returned to crates to
ripen. The stems should be removed when the best color is desired,
and the tomatoes should be thoroughly washed to remove dirt and mold.
Dumping a crate of tomatoes into a hopper of dirty water and playing a
gentle spray of water on part of them merely wets the skin and makes
them appear bright.

[Illustration: Fig. 2.--Large receiving room showing the sorting belt.]


PULPING.

The clean tomatoes should be conveyed to the steaming tanks and
subjected to steam heat until the skins burst and the meat softens.
After a short heating the tomatoes should be run through a “cyclone”
where the skins, seeds, etc., are removed and they are rubbed to a
pulp. To remove very small particles and fiber, the pulp may be run
through a sieving machine at once; or, if ketchup of the smoothest
possible kind is to be made, this procedure should be delayed until
after the cooking. The pulp is collected in a receiving vat, and
only such an amount should be provided in advance as will keep the
kettles full, as it is better to stop the tomatoes before going to
the washer than to have the pulp stand for some hours. In common
practice, however, the pulp is either sent to the cooker at once, or
it is allowed to stand and partially separate. If tall casks are used
for this separation the solids will rise to the top and the clear
watery portion is drawn off at the bottom, or the pulp may be strained
through cloth bags. The object of this separation is to secure greater
concentration of the solids, retain a brighter color, and shorten the
time of cooking.


COOKING AND SEASONING.

[Illustration: Fig. 3.--A section of a kitchen showing the copper
cookers.]

The cooking may be done in copper kettles, as shown in figure 3, though
these are being superseded by enamel tanks containing silver-plated
coils in order to secure the brightest color. By using the latter the
discoloration due to the splashing of the contents against the walls of
the copper vessel is avoided, and economy of space is secured. Whole
or ground spices, or acetic acid or oil extracts of the spices may be
added to the pulp in such proportion as the particular brand demands.
The spices most used are cloves, cinnamon, mace, and cayenne pepper;
but paprika, pepper, mustard, cardamon, coriander, ginger, celery, and
allspice are used by some manufacturers. When whole spices are used,
it is the practice to suspend them in a cloth bag or a wire basket and
to take them out after boiling. They tend to darken the color of the
ketchup, a result considered undesirable by some. The ground spices
are used sparingly, with the exception of cayenne pepper. The acetic
acid extracts of spices are used because they are economical and give
a brighter red color than is obtained with the whole spice. The oil
extracts produce no discoloration, but they are the most expensive and
give an objectionable flavor. Hungarian sweet paprika is now quite
largely used and adds to the color as well as to the flavor. Sugar,
salt, and vinegar are added in such proportion as may be desired, and
in some brands onions and garlic are used.


EVAPORATION AND FINISHING.

The pulp is evaporated rapidly to such consistency as the grade and
price will warrant, the reduction in volume being from 40 to 60 per
cent. This is accomplished in about forty-five minutes. The cooking is
not continued longer than is necessary, as each minute added to the
cooking darkens the finished product.

If the pulp has been run through the sieving machine before cooking,
the batch may be drawn off into the receiving tank for bottling. If the
finishing be done after cooking, the pulp is run into a receiving vat,
finished as quickly as possible, and drawn into the tank for bottling.
The ketchup may be kept at a high temperature--200° to 206° F.--in the
receiving tank by means of a small steam coil, or it may be drawn to
the bottling machine through a steam-jacketed tube. Finishing after
cooking yields a slightly smoother ketchup than sieving before cooking;
but it necessitates handling, reduces the temperature, and increases
the chances of infection.


BOTTLING.

The bottles should be thoroughly cleaned as ketchup will not keep if
placed in bottles which have been merely rinsed to remove the straw; if
the ketchup is not to be given an after process the containers should
be sterilized. In the experimental work cork stoppers gave the best
results and these should be sterilized in a paraffin bath at 250° F.


PROCESSING.

An after treatment or process is given to bottled goods either in a
water or steam bath, the important point being that the center of the
bottle be raised to the desired degree of heat. If the ketchup is thin
this can be effected quickly, but if it is thick and heavy the heat
penetrates the ketchup with surprising slowness. In a thin ketchup
the temperature may be raised from 140° to 190° F. in eighteen minutes
or less when the surrounding heat is 195° F; but in a heavy ketchup it
may take an hour or more to accomplish the same result. It is therefore
very important that the ketchup be processed immediately after it is
corked, before it has time to cool. The rate at which the heating is
effected for different goods can be determined by sealing a thermometer
in the cork and recording the readings.

[Illustration: Fig. 4.--An example of factory practice showing the
top row of tanks from which pulp passes by gravity into the cookers,
then into the receiver, sieving machine, and final tub ready for the
bottling machine or jug filler.]




CHARACTER OF PRODUCTS.


FIRST-CLASS PRODUCTS.

The factory at which the experiments were conducted has sanitary
buildings and surroundings, the floors are of concrete for flushing,
and the pipes used in conducting the pulp to the kitchens are
porcelain-lined to prevent discoloration from the iron and to insure
cleanliness. The tubes which carry the ketchup from the kettles to the
receiving tank, finishing machine, and bottler are silver-plated. Not
all of these measures are necessary to make a good ketchup, but they
show the care exercised in making an article of good appearance and of
the finest quality.

The conditions under which ketchup is made and the care with which the
work is done at some of the better factories is equal to that used in
the manufacture of any food product. Whole selected fruit is used,
cleanliness is maintained at every point, the best grades of spices,
vinegar, granulated sugar, and salt are added for flavoring, and the
bottles are carefully washed. The ketchup put up under such conditions
will have a bright natural color, will remain good as long as the
container is unbroken, and will continue in that condition for some
time after opening if kept at a fairly cool temperature.


INFERIOR PRODUCTS FROM “TRIMMING STOCK.”

In contrast with the strictly high-grade product is the great bulk
of the ketchup found on the market. The material is not whole ripe
tomatoes, but consists of the waste of the canning factory, commonly
designated as “trimming stock,” including the green, moldy, broken,
rotten, and generally unusable tomatoes, the skins, cores, and stems
from the peeling tables, and the surplus juice from the filling
machines, all of which may be allowed to stand during the day and be
run through the cyclone in the evening. At the end of the season, the
frosted and half-ripe fruits may be used. Part of this material can
not be considered “sound fruit” as contemplated by the food and drugs
act. The pulp is put up in barrels, preserved, and allowed to stand,
possibly in the sun, until a sufficient quantity has accumulated for
shipment. Old ketchup barrels may be used and be none too clean. As a
result, it is not uncommon to see an inch or more of pulp in the bottom
of a car at the end of shipment, caused by the blowing out of the
barrel heads from fermentation. The sanitary condition of the factory
may be poor, the handling of the goods be unclean, the spices be the
refuse from the spice houses, the sugar be of the cheapest grade, and
the bottles be only rinsed or be used without even that precaution.
The ketchup is a concoction so heavily spiced with hot spices that the
tomato flavor is lost and might as well be anything else. The color is
normally dirty brown.

Between these two extremes are all grades, those for which whole
tomatoes, unsorted, are used, those for which trimming stock is worked
up promptly during the canning season, and those made from stock of
unknown history. Some manufacturers work under good and some under poor
sanitary conditions. There can be no doubt that with proper selection
and precaution much of the by-product of the canning factory and large
quantities of tomatoes which are unsuitable for canning might be used
to advantage in the manufacture of ketchup; but it requires a nicety
of practice not generally found at this time. The practice sometimes
followed