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EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP.
EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP.
Issued January 9, 1909. U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF CHEMISTRY—BULLETIN No. 119. H. W. WILEY, Chief of Bureau. EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP. BY A. W. BITTING, INSPECTOR, BUREAU OF CHEMISTRY. WASHINGTON: GOVERNMENT PRINTING OFFICE. 1909. WASHINGTON: GOVERNMENT PRINTING OFFICE. 1909. 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 experi
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PROCESS OF MANUFACTURE.
PROCESS OF MANUFACTURE.
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 perf
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SELECTION AND PREPARATION OF STOCK.
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 tomat
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PULPING.
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 i
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COOKING AND SEASONING.
COOKING AND SEASONING.
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 spice
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EVAPORATION AND FINISHING.
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 r
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BOTTLING.
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....
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PROCESSING.
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 ho
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INFERIOR PRODUCTS FROM “TRIMMING STOCK.”
INFERIOR PRODUCTS FROM “TRIMMING STOCK.”
During the season tomatoes come in at times in larger quantities than can be made into ketchup promptly. The surplus must be worked up into pulp for storage and may be stored in barrels or in tin cans. The pulp stored in barrels will not have as good a color as that put into cans, and the ketchup made from either will not be as bright as that made from whole, fresh stock. The pulp put up in barrels is more liable to spoilage than that put up in cans. The difference in the cost of storage by the
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LABELS.
LABELS.
The labels on the ketchup bottles have been improved somewhat in the last year as regards exactness in describing the contents. Formerly, according to the labels, much of the ketchup was made from whole ripe tomatoes. The question was, What became of the enormous amount of ketchup which it was known had been made from “trimmings?” On this year’s ketchup the labels make fewer claims, generally merely stating that it is “tomato ketchup,” which is true whether made from whole tomatoes or refuse. Th
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OUTLINE OF THE EXPERIMENTS.
OUTLINE OF THE EXPERIMENTS.
Experiment No. 11. —Pulp was made in the usual manner and run into barrels while just below the boiling point. The barrels had been thoroughly washed and then steamed for twenty minutes. As soon as the pulp had cooled slightly the bung was driven in tightly and the barrel was rolled into storage. At the end of sixty days the barrels were opened and the pulp was found to be in good condition. Experiment No. 12. —Regular ketchup was drawn into 5-gallon jugs which had been sterilized in the same ma
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DISCUSSION OF RESULTS.
DISCUSSION OF RESULTS.
Twelve hundred and ninety-six bottles were shipped from Terre Haute to Lafayette, Ind., and some were reshipped in order to duplicate the conditions in trade. Some were kept in a warm temperature and in strong light, others in a comparatively cool place and in the original shipping cases, in order to duplicate the conditions in the warehouse and grocery store. There has been no spoilage after ten months other than that resulting from four or five cork leaks and neck cracks. These experiments hav
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SALT.
SALT.
The yeast was checked slightly by 5 grams, and very materially by the 10-gram solution, as it required two days for a thin, delicate film to form, whereas in ordinary solutions a rather thick film is formed within twenty-four hours or even in less time. There was no development in the 15-gram solution....
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SUGAR.
SUGAR.
The effect of sugar was tested on both the mold and the yeast by adding it to tomato bouillon. It was supposed that a low percentage of sugar like the salt would plasmolyze the cells, and in this way check growth, but it seemed to have no effect until the amount was increased to 25 grams per 100 cc of bouillon. In this solution growth appeared as soon as with the weaker solutions, but there was a smaller amount. In the 25 to 40 gram solutions there was less development as the amount of sugar inc
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SPICES.
SPICES.
Experiments to determine the value of the spices as antiseptics were made, using water infusions, acetic-acid extracts, and oil extracts. In making the water infusions 20 grams of the whole spices, with 200 cc of water, were boiled for forty-five minutes. This is approximately the length of time that the spices are cooked in the ketchup in the factory. The liquid was then filtered and from 0.1 to 5 cc of the filtrate was used in 10 cc of tomato bouillon. The same organisms were used as in the fo
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VINEGAR AND ACETIC ACID.
VINEGAR AND ACETIC ACID.
An experiment was made to determine the antiseptic value of vinegar and acetic acid. Commercial 50-grain distilled vinegar was used. It was found that when 30 per cent of this vinegar was added to the tomato bouillon the development of mold was checked and the extent to which it was checked increased with the increased amounts of vinegar. The development in the solution containing 30 per cent of the vinegar was two days later than the normal in starting, while the solution containing 100 per cen
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OIL.
OIL.
In ketchup manufacturing it is customary, if an agitator is not used, to put a small amount of fat in the kettle to check the ebullition during the reduction of the pulp. The amount used in this manner is not sufficient, however, to be apparent in the ketchup. Brannt [D] states that in some factories, where the trimmings are allowed to accumulate for the season, they are given liberal doses of oils and condiments when cooked, in order to disguise their defects, so that the product can be placed
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DEVELOPMENT.
DEVELOPMENT.
In developing, the mold forms a white felt-like mass, covering the medium on which it is growing; then as development proceeds, it changes to bluish-green, and finally to a darker, duller color. The change in color is accompanied by a change in structure, the surface becoming powdery in appearance, a slight current of air being sufficient to dislodge a cloud of fine dust. This fine dust is formed of small, spherical bodies, the spores or conidia (from the Greek meaning dust ). These need no rest
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REPRODUCTION.
REPRODUCTION.
After a shorter or longer period of development, dependent on the conditions, branches are sent perpendicularly from the substratum, and into the air. These branches cease their growth in length, sending out branches near the tip, which take the same general direction as the original branch. Each of these subbranches is called a sterigma (from the Greek word meaning support ). In vigorous development the sterigmata may form secondary branches, the whole forming a tassel-like arrangement. The tip
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GROWTH IN KETCHUP.
GROWTH IN KETCHUP.
The form of Penicillium which was used in the experiments was isolated from ketchup in which it grew luxuriantly. When conidia are first formed on the ketchup, they are a delicate blue in color; they then become bluish green, then green, and finally olive. The development of the color of mold growing on ketchup is practically the same as when grown in wort, tomato bouillon, pea bouillon, or gelatin made with these solutions as a basis. In ketchup containing sodium benzoate, the blue color appear
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TEMPERATURE TESTS.
TEMPERATURE TESTS.
The limits for the germination of Penicillium, as given by W. J. Sykes, [E] are 2° to 43° C. (35° to 110° F.), and the most favorable temperature 22° to 26° C. (72° to 79° F.). This author states also that according to Pasteur the dry spores retained their vitality at 108° C. (226° F.), but that they were soon killed when immersed in boiling water. Klöcker [F] quotes Pasteur as saying that the conidia are killed if exposed to a temperature of 127° to 132° C. for half an hour, but that they retai
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HISTOLOGICAL STRUCTURE OF KETCHUP.
HISTOLOGICAL STRUCTURE OF KETCHUP.
In ketchup are found parts of all the various tissues of the tomato broken into fine pieces by the action of the cyclone. Although the sieves take out the seeds, skins, and any large pieces, particles of the various tissues are present in size sufficient for identification. Among the distinctive features are the red crystalline bodies in the parenchyma, which serve to a certain extent to distinguish the parenchyma from that of other plants which might be used for adulteration, and serve also to
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MICROSCOPIC EXAMINATION OF SOME COMMERCIAL BRANDS.
MICROSCOPIC EXAMINATION OF SOME COMMERCIAL BRANDS.
In examining ketchup the color, odor, amount of discoloration, presence of foreign tissue, foreign coloring matter, oil, and fungi were determined. If no preservative was mentioned, some of the ketchup was put in petri dishes and inoculated with Penicillium to determine whether growth could take place. The following examinations are reported, as they represent some of the best known brands on the market: No. 9. —Opened September 2, 1907; age unknown; pint bottle; no preservative mentioned; not s
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SUMMARY.
SUMMARY.
1. The experiments made during the season of 1907 on the manufacture of tomato ketchup without chemical preservatives were conducted under factory conditions and upon a commercial scale. The results prove that such a ketchup can be made and delivered to the consumer in perfect condition; the product in question having already stood ten months, unopened, without showing the slightest indication of spoilage. 2. The product is of excellent consistency, flavor, and color. The formula employed regula
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