THE MANUFACTURE OF TOMATO PRODUCTS TEXT

right, while when a larger number is present the product is said by the government to consist in whole or in part of a filthy, decomposed, putrid vegetable substance? Aren’t such foods as Roquefort cheese, cottage cheese, buttermilk, and sauerkraut fairly swarming with the same kinds of germs as tomato pulp? Aren’t these foods all considered healthful? Then why object to these germs in tomato pulp? Aren’t the germs all killed by the boiling, anyway? These are questions often asked by pulp packers, and it is hoped that the following will throw some light on the subject. Molds, yeasts, spores, and bacteria are very tiny plants, not animals. They are so small that they can only be seen by the naked eye when there are very large masses of them together, consisting, in the case of bacteria and yeasts, of hundreds of millions of small individual plants, and in the case of molds, of many individual mold plants closely massed together. You have all seen large tufts of white mold on tomatoes, and black mold covering a loaf of bread, but you probably did not realize the enormous numbers of individual mold plants that were present, or the rapidity with which they multiplied themselves. You have all seen swelled cans of tomato pulp, and after the cans were opened you have noticed the bubbles rising in the pulp, and have noted the very sour taste and often an extremely disagreeable odor. In every thimbleful of that sour pulp there were hundreds of millions of bacteria and yeast cells, so small in size that many thousand could collect at the same time on the point of a pin and they would not be noticed by the naked eye. It was these tiny bacteria and yeast plants which caused the physical and chemical changes in that pulp. Just as a parasitic vine winds itself around a tree and sucks the life out of it, so these millions of bacteria and yeast plants sucked all the goodness out of this tomato pulp, and left nothing but sour, decomposed tomato fiber, acid, and foul-smelling gas. Molds The structure of the mold plant is similar to that of a very small vine, the branches of which are many and are closely massed together. The tiny threads or filaments of mold resemble the vine and its branches. These threads keep sending out new shoots which spread rapidly all over the surface the mold is growing on, and the fruit of the mold plant, which is called spores, is similar to the little berries which grow at the ends of the branches of a vine. These berries are the fruit of the vine; spores are the fruit of the mold plant. Just as the berries contain seeds which reproduce the plant, so the tiny spores contain the seed which will reproduce the mold plant. These spores grow at the end of the mold threads or branches, and when ripe, either fall on the surface directly beneath, or are carried away by a breath of air and move along with the dust. The spores of the mold plant will remain alive for months in a dry state, floating in the air, or if the air be very still, falling to the surface. The air everywhere is full of them, and as soon as they light upon a moist surface, such as tomato juice, for example, which contains nourishment for them, they begin to send out shoots of mold threads and reproduce another mold plant. [Illustration: Fig. 4.—Mold filament from catsup. (×150.) ] Mold grows most rapidly upon a warm surface, preferably about the temperature of the human body. It will not grow on a surface which is at freezing temperature, or on a very hot surface. Under these extremes of temperature it is unable to multiply itself. Boiling kills the mold plant, and continued boiling of 15 minutes or more also kills the seeds or spores of practically all species. That is one reason why it is desirable to bring peeled tomatoes or tomato juice to a boil as soon as possible—so that the mold and mold spores which are always on these surfaces will be killed before they have an opportunity to grow. There are many different species or varieties of mold plants which thrive on tomatoes and tomato pulp, but they are all very similar; they reproduce themselves in exactly the same way, and they are all arrested in their growth by extremes of temperature, and are killed by continued boiling. It should not be thought, however, that boiling for a very few minutes will kill all mold spores, as they have a tough surface which has considerable resistance to heat. I have seen 5–gal. pulp packed which was only given a very short boil on account of low steam pressure, and molds grew in the sealed cans after packing to such an extent that the pulp all had to be thrown away. It is safe to assume, however, that a 15–minute boil will kill mold spores and prevent the growth of molds in the cans after they are sealed, providing, of course, that the pulp is filled hot into cans which are clean and almost sterile. Bacteria Bacteria and yeasts are very much smaller plants than molds. While an individual mold plant, growing as stated above like a very small vine, branches out and spreads over considerable surface, bacteria (that is, those forms in which the pulp packer is interested) are very short, single rods, which, when multiplied in size 500 times by the microscope, appear to be from 1/32 to ⅛ of an inch long. Yeasts, when multiplied in size 500 times, usually appear to be from two to five times as large as a pin head. The rod-shaped bacteria referred to above are mainly the lactic acid, and acetic acid bacteria, both of which produce fermentation in tomato products. The lactic acid germ is the same one which causes milk to sour, while the acetic acid germ is the one which produces the acetic acid of vinegar. There are many other kinds of bacteria in tomato pulp, many of which are small, round cells. However, the bulk of these probably come from the soil and are natural to the tomato, and are not counted when the number of bacteria per cubic centimeter are estimated. The rod-shaped types indicate fermentation. [Illustration: Fig. 5.—Rod-shaped bacteria from tomato pulp, common in bad catsups. (×500.) ] Bacteria reproduce themselves with amazing rapidity. It has been found out by watching them multiply under the microscope that under favorable conditions one germ reproduces itself every 30 minutes, and in some cases reproduction is known to have been even more rapid than that. The method of reproduction is by simple division. The rod-shaped bacterium is just like a match in shape, only many thousand times smaller, and in the space of about 30 minutes it will divide itself in the middle, thus changing itself into two shorter rods. Each of these rods grows in length, and each of them then divides, making four rods. In 30 minutes more the four rods change into eight, etc. It is the simplest method of reproduction there is. Bacteria also have another method of reproducing themselves which they resort to when conditions become unfavorable for their growth and they can no longer multiply themselves by the simple division method. Such an unfavorable condition would be the drying up of the moist surface on which they are growing. In this case the rod-shaped bacterium forms one or more spores within itself. These bacteria spores are somewhat similar to mold spores, but are much smaller. However, they are only produced by bacteria under unfavorable conditions, while the mold plant produces them under all conditions. The bacteria spores, like mold spores, have a tough surface which gives them high resistance, and they contain the germ of bacteria life which can reproduce the species when favorable conditions for growth are again encountered. The bacteria spores, therefore, float through the air as do the mold spores, remaining in the dry state without nourishment for months at a time, and as soon as they light upon a moist surface containing the elements for growth, even to a very small degree, they reproduce the rod-shaped bacteria form, which begins to multiply itself again by the simple division method. Although most bacteria spores are killed by boiling for 10 or 15 minutes, there are a few species of extremely high resistance which have been known to remain alive after several hours’ boiling. Spores of this nature are infrequent, however, and the packer might as well forget that they exist. Not one case of spoilage out of a hundred is caused by the presence of such spores, and if all food products were cooked a length of time sufficient to kill all bacteria spores which might possibly be present, the foods would be cooked to death, and unfit to eat. Yeasts Yeasts are very tiny individual cells, and multiply by budding, instead of by simple division, as bacteria do. Instead of the yeast cell dividing in half, thus producing two cells, it remains intact, but a bud forms on its outer surface. This bud grows in size until it becomes almost as large as the cell which produced it, and then it separates from the mother cell, and we have two yeast cells. Each of these two cells then produces buds, which again separate, and so on. Like bacteria, the multiplication is very rapid under favorable conditions. Favorable conditions for yeasts and bacteria are the same as they are for mold, that is, a warm temperature, preferably near blood heat, and a moist substance which is not too strongly acid, and which contains the elements necessary for growth, preferably the natural sugar of fruits and vegetables. [Illustration: Fig. 6.—Yeasts and spherical bacteria from decaying tomatoes. (× 500.) [The oval bodies are the yeasts, some in budding stage; the bacteria appear as small spheres, or pairs of spheres.] ] Yeasts are the principal gas-forming agents in the fermentation of pulp. In the production of this gas they consume the natural sugar of the tomato. They will multiply by the budding method described above as long as they are in a medium which is favorable for their growth. As soon as this medium drys up, or for some other reason becomes an unfavorable medium for the multiplication of the yeast cells, the yeasts resort to spore forming, just as bacteria do. These spores are formed within the yeast cell, and when the cell wall breaks the spores pass off into the air. Like all other spores, they have a high resistance, and will float around in the dry state and remain alive for a very long time. When they light upon a medium in which they can grow they reproduce the yeast species, in the same manner in which the bacteria spore reproduces the bacteria species from which it was derived. Spores The spores, then, which are found in tomato products are of three different kinds, namely, mold spores, yeast spores, and bacteria spores. The greater number are almost always mold spores, since the mold plant produces spores under all conditions, while yeasts and bacteria only produce them under unfavorable conditions. When microscopical analyses of tomato products are reported, the mold spores and yeast spores are included with the yeasts in the term “Yeasts and Spores.” This is because a large number of the spores are very similar to yeast cells in appearance, and as it would be a laborious process for the analyst to separate them, the yeasts and spores are included in one figure, which greatly simplifies the analysis. The bacteria spores are not included in the count of “Yeasts and Spores.” How Germs Retard Their Own Growth We will say that we have stacked away a 5–gal. can of pulp which contains several living spores of bacteria, as is apt to be the case, since the air is full of them, and the pulp is constantly open to contamination from the air after it is cooked; also the spores may be in the empty cans at the time they are filled. Why is it, since these few spores are alive, and in a favorable medium for their growth, that the rod-shaped bacteria forms which they produce do not multiply to such an extent that they will ferment the can of pulp. It was stated above that bacteria do not multiply in a strongly acid medium. Since the bacteria produce acid as a by-product of their own growth, they surround themselves with an acid medium, and they thus retard and finally stop their growth by the product of their own reproduction. When this acid medium reaches a certain strength the bacteria can no longer multiply, and if that can is not moved until used, the chances are it will be all right when opened. But if the can is moved, the contents are agitated, and these living bacteria are shaken away from the acid medium in which they have been suspended, and they are shaken into a fresh, sweet medium in which they can again begin to multiply. It may therefore follow that if this can is moved several times it would be at least partly fermented when opened, while if it was left alone it would have remained sweet. This illustration shows the desirability of moving pulp as little as possible, and as carefully as possible when moving becomes imperative. The lack of air in the can will, of course, also retard bacterial growth, but there is usually a small amount of air in the can, and many species of bacteria do not need any air whatever for their growth. [Illustration: Fig. 7.—Mold spores and filaments. A type frequently found in decaying tomatoes. (×300.) ] Rapidity of Growth Yeasts and bacteria multiply more rapidly than do the molds, and that is why pulp which is made from tomatoes or tomato peelings which are handled slowly or carelessly usually shows a high content of yeasts and bacteria, while the molds may be low. As a rule, most of the mold found in pulp was present in the original tomatoes, and is found in the pulp because it wasn’t eliminated in the sorting. But, as a rule, tomatoes are not full of yeasts and bacteria unless they are very soft and mushy, and it is evident on looking at them that they have fermented to some extent. If pulp contains a high count of yeasts or bacteria it usually means that this fermentation took place in the factory at some stage in the manufacturing process, or that the product has been contaminated by fermented tomato substance lodged in pipes, troughs, and conveying equipment. Often it is due to delay in getting the tomato stock to a boil. The laxness in this regard in some factories is surprising, and their pulp is almost always high in yeasts and bacteria. When you consider the extreme rapidity with which these germs multiply, the folly of allowing tomato peelings or tomato juice to be very slowly conveyed to a large tank for an hour or more before the steam is turned on becomes apparent. Much has been written about the rapidity of bacterial reproduction, and yet extreme delay in working up tomato stock continues in many plants, and we frequently see bacteria counts of a hundred million or more per cubic centimeter, all of which could be easily avoided if the packer would just make up his mind to get to the bottom of the cause and apply the simple remedy. Just as an illustration we will say that we are putting up trimming pulp, and the tomato receipts are rather light and the peelers are working slowly, or that there aren’t many peelers working. The trimmings are passed along on a belt conveyor where they go to a bucket carrier and are lifted to a large cypress tank with a coil. They drop into the tank slowly, and it may take two hours for the coil to be covered so that the steam can be turned on; or after a foot or two of the trimmings have been put in the tank it is lunch time, and it is an hour before the filling of the tank continues. This may make it three hours before these peelings are brought to a boil. Suppose at the time those peelings go into the tank they contain enough bacteria so that if they were cooked at once, the pulp would run 10 million to the cubic centimeter. This is very probable. However, they are not cooked at once and at the end of 30 minutes you have peelings which, when condensed and cycloned, would show close to 20 million bacteria. In an hour the first peelings which entered that tank would yield 40 million, and in 1½ hrs., 80 million. This is on the basis of the bacteria reproducing themselves every 30 minutes. Even if they multiply much more slowly than that you can see that in the course of a little over an hour you are getting into dangerous ground, and in the course of two or three hours the bacteria have multiplied to such an extent that the product would almost be sure to be condemned if it was picked up by an inspector. If the tomatoes had quite a few soft spots in them when they were peeled it is very likely that the peelings would yield 20 million bacteria if worked up immediately, and then if delay of an hour or more comes on top of that you can see where you will be on the bacteria count. The yeasts are also probably multiplying at the same time, and the molds are growing to some extent. Now what this packer should do is to put a small open steam jet in the bottom of his cypress tank, with four pipes running horizontally, as in a “breaking tank,” and turn on the steam as soon as the peelings cover these pipes, which lie right on the bottom of the tank. The peelings are thus kept at a boil until the steam can be turned on the coil, and then the steam from the open jet can be shut off. This is a very simple arrangement to make and will save no end of trouble. It must not be thought that because micro-organisms multiply most rapidly in a warm medium they will not multiply in a cold medium, or one which is considerably warmer than blood heat—the degree of temperature most favored. The only safe extremes are 33 degrees F. for the lower extreme, and 150 degrees F. or above for the higher extreme. Anywhere between these two extremes of temperature there is danger of germ activity, and the nearer the medium is to 98 degrees F., the more rapid is the multiplication of the germs. As tomato juice contains all the nutritive requirements for the growth of micro-organisms, and is not strongly acid, it is an ideal medium for them to grow in. There doesn’t seem to be any medium whatever that molds, yeasts, and bacteria prefer to tomatoes and tomato juice. The Government Attitude on Micro-Organisms What are the objections of the pure food authorities to the presence of large numbers of micro-organisms in tomato products, and how do they substantiate their objections? We know that all of these germs that grow in tomato products are harmless. Even if an occasional harmful germ should enter it would not be discovered by the method of analysis employed, and unless it was in the spore form and of extremely high resistance it would be killed by the boiling. We know that buttermilk and sauerkraut are full of bacteria, and that the latter is also full of yeasts, and that these two foods are recommended by physicians as being particularly healthful because of the lactic acid they contain, which is produced by the lactic acid bacteria—the same kind that are condemned in tomato products. In sauerkraut we know that these lactic acid bacteria and yeasts are killed by the cooking, just as they are in tomato products, which seems to make the two cases analogous. In buttermilk and cottage cheese, however, they are alive and growing, and these products are considered healthful. Roquefort cheese is full of a green mold which gives it its characteristic flavor and color, and it is considered healthful. Then why object to molds in tomato products? The difference is that in one case we have a controlled and regulated fermentation, which is confined to one or more species, which in combination with the characteristic elements of that particular food produce a healthful by-product or desirable flavor. In the other case we have an unregulated and uncontrolled fermentation, produced by a variety