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.