THE MANUFACTURE OF TOMATO PRODUCTS TEXT

at 210 degrees F., it will contain about 1,010 cubic centimeters of pulp at 200 degrees F., or possibly lower. One reason for this delay is that the foam caused by filling the flask with boiling pulp rises in the neck of the flask, and makes it hard to judge when the flask is exactly full. The main difficulty with the method, however, is that pulp cooks do not have scientific minds, they do not appreciate the importance of doing the determination in a strictly scientific way, and the results they get are not very accurate. I have frequently checked up on pulp cooks using this method, and sometimes they were very decidedly off. Testing With Hydrometer The estimation of the gravity of the boiling pulp by the use of a hydrometer is not in very general use, and it has been stated by some scientific men that a hydrometer is no good for tomato pulp or catsup except where the sample on which the test is made is previously filtered so as to get a clear liquid. A test which involves filtering, is, in my opinion, entirely unsuited for everyday use on the cooking platform. I have used the hydrometer for testing pulp and catsup direct from the kettle for seven years, and have had more success with this method than with any other. The hydrometer was never intended to be used with semi-solid substances such as tomato pulp, but only with liquids such as brine, sugar syrup, etc., in which there is no solid matter in suspension. With liquids, the number of degrees registered on the hydrometer when it is immersed in the liquid is equal to a definite specific gravity. This is not true with semi-solids such as tomato pulp, as each packer must work out the relation between the degrees of the hydrometer and the specific gravity on pulp under the conditions which obtain in his plant. This is a very simple thing to do, and once the packer has established this relation, it will hold good as long as he is in the pulp packing business. The reason why this relation is not the same for all packers is because tomato juice is not screened to the same degrees of fineness in all plants, and because all hydrometers having the same scale will not work the same on pulp. This is because they have different shapes. The shapes may only vary slightly, which will not interfere with their accuracy on clear liquids, but it will make a difference when the hydrometer is used in tomato pulp. Furthermore, some of the hydrometers will probably have too much variation in their diameter at different points, which is a disadvantage when they are used in tomato pulp. I have therefore always had the hydrometers which I have used for this test made to order and to conform to certain specifications which I laid down. [Illustration: Fig. 3. Special hydrometer for testing tomato pulp and catsup. (C. J. Tagliabue Mfg. Co.) ] In Fig. 3 is illustrated a hydrometer which is manufactured by the C. J. Tagliabue Mfg. Co. of Brooklyn, and which is made to conform to these specifications, which are: first, perfect balance; second, a minimum amount of variation in the diameter of the various parts of the spindle with the slope very gradual; third, a Beaume scale reading from 0 to 50 degrees; fourth, that it can be obtained in exact duplicate in any quantity. If the diameter at various points in the spindle is slight, with the slope very gradual, it seems to be an advantage. It is, of course, necessary that exact duplicates can be obtained to use when the first one, on which your calculations are based, is broken. In order to avoid disappointments which would be very apt to result from the use of a hydrometer which was not particularly adapted to this test, and which would very likely be difficult of exact duplication, the type illustrated above should be adhered to, and it will be found to give good results when used as directed in this chapter. Two pulps of the same specific gravity, and of practically the same degree of fineness, if tested hot, will register the same on the same hydrometer, or on two hydrometers which are exactly alike in every respect. (The hydrometer does not work well on cold pulp unless the pulp is thin.) Two pulps of the same specific gravity, showing a very marked difference in their degree of fineness, will not register the same on the same hydrometer, because, even though a definite volume of each will weigh the same, the two pulps are of different thicknesses, which will have an effect on the degree to which the hydrometer will sink when placed in the pulp. However, if a packer cyclones his tomatoes before condensing them, and uses the same mesh of wire screen in his cyclone all the time, his pulp will all be of the same degree of fineness, and this point is eliminated. Every pulp packer who cyclones his tomatoes, and who uses the same mesh of screen in his cyclone throughout the season, can use the hydrometer for testing his pulp and can obtain uniformity without the use of any complex apparatus. The relation between the hydrometer reading and the desired specific gravity is arrived at as follows: When the boiling pulp approaches the finishing point, pour a sample into a tall gallon measure and take the hydrometer reading immediately. Save this sample, put it through the finishing machine along with several additional gallons dipped from the kettle so as to get a good sized sample through the finisher, taking care that the brushes are dry so as not to dilute the sample, and have the specific gravity determined on this finished sample when it gets cold. Take other samples from the kettle at five-minute intervals, and save them for the same purpose, after getting the hydrometer reading. We will say that one of these samples, when tested for specific gravity, ran 1.035. The packer looks up the hydrometer reading he got on this sample, when taken hot from the kettle, and finds the reading was 18 degrees. He then knows that for pulp of the degree of fineness he gets from his cyclone, 18 degrees on his hydrometer equals specific gravity 1.035 after finishing. He may also find that for the sample that was taken from the kettle five minutes later, specific gravity 1.04 is equivalent to 24 degrees under the same conditions. He now has established a relation between the degrees on his hydrometer and the actual specific gravity. (The reason for putting the pulp through a finisher before determining the specific gravity is that he wants to make this test under the same conditions that the buyer would make it.) Now, if the packer decides that he wants to condense his season’s run of pulp to 1.035, he simply cooks it all to 18 degrees on his hydrometer, providing this is the comparison he got. Under his conditions he may find that 16 or 20 degrees equals specific gravity 1.035. As stated before, each packer must determine this for himself. Method of Using Hydrometer The cook should fill a tall gallon measure with the boiling pulp and allow the spindle to sink into it slowly. Do not drop it into the pulp so that it will fall suddenly, as the weight of the mercury or shot in the bottom will carry it farther than it should go. It will be noticed that the spindle will sink rapidly for a few seconds and then almost come to a standstill. At this point—when a standstill is almost reached—the reading should be taken. It requires quite a little time to reach an absolute standstill, and this is not necessary, as it is easy, with a little practice, to catch the other point and take the reading. After the reading is taken, lift out the spindle, stir the pulp with it, and allow it to sink again as a check determination, merely for the satisfaction of being doubly sure. You will find that you get the same reading unless you wait so long before making the check determination that the sample has had a chance to cool considerably. As the test only takes ten seconds, the two tests can be made in a half minute at the most, which gives the pulp no chance to cool. The hydrometer method is not absolutely fool proof, but it is as near fool proof as anything I know of. Neither is it the acme of perfection in a pulp testing method, but it is, in my opinion, far better than anything that has been suggested to date. It is simple, and accurate enough for all practical purposes, and any ordinary laborer can be shown in a few minutes how to make the test, and the chances of error are very small indeed. This method will not work where crushed tomatoes are being condensed. It is necessary that the tomato juice be previously cycloned. The pulp must be homogeneous and not lumpy and full of skins to be capable of being tested by the direct hydrometer method. When determining the finishing point on crushed tomatoes it is best to use either the eye or the specific gravity test by weighing. Finishing the Cooking The steam should be kept on the kettle continuously until the batch is done. While testing is being done it is not necessary to shut off the steam. If salt is used it should be scattered over the batch slowly a few minutes before it is done. Salt increases the specific gravity, and also the hydrometer reading. The relation between the hydrometer reading and the specific gravity can be worked out just as well where salt is used as when it is not used. The addition of salt does add to the flavor, and some buyers prefer it, while others do not. I have seen buyers pick out a poor quality pulp with salt in it in preference to a much better quality with no salt. As soon as the steam valve is closed the exhaust should be opened to discharge the steam from the coil or jacket and allow it to cool as quickly as possible. It is often necessary to hold batches in the cooking kettles for some time after the cooking is finished. This darkens the pulp some, both because of contact with the air, while hot, and from long contact with the sides of the kettle or coil, which remain hot. Cooked pulp should therefore be discharged from the kettle just as soon as possible. If held over 30 minutes in the kettle it should be given a momentary boil before letting it down. Be careful to avoid contamination in the kettle after the steam is shut off, such as cold dirty water dripping in from rafters overhead, and leaks from pipes over the kettles through which cold tomato juice is flowing. Such material will not become sterilized merely by contact with the hot pulp, and may cause swells in the canned product if there is very much of it. CHAPTER V CONVEYING THE CONDENSED, STRAINED, OR CRUSHED TOMATOES TO THE FINISHING MACHINE AND FINISHING SAME Conveying to Finisher The fewer pipes and receiving tanks the condensed pulp passes through before being filled in the cans, the better. All of this conveying and finishing equipment offers possibilities of contamination, and allows the cooked pulp to cool to some extent before it is filled. Eliminate as much equipment as possible between the cooking kettle and the filler, and have the pulp enter the cans at at least 170 degrees F., and if possible, at 180 degrees or above. A receiving tank between the cooking kettles and the filler should be dispensed with if possible, and the finishing machine draw the cooked pulp direct from the kettle by means of a short line of enamel lined pipe. Receiving Tanks Unfortunately the arrangement of many plants is such that it is almost necessary to use a receiving tank; at least in such cases it would be a disadvantage not to have one. Where a tank must be used here it should be in such a position that it is easily accessible, so that it will not be necessary for a man to be an acrobat to get into it, inspect it, and see that it is kept clean, and that an inch of pulp is not allowed to lie in it and get cold while waiting for another batch to come down. The best kind of a tank for this purpose is an enamel or glass-lined tank with a rounded, tapering bottom so that it will almost drain itself completely, and what little adheres to the sides can be scraped down in a few seconds if it is necessary to wait five or ten minutes for a fresh, hot batch to come down. Even if it isn’t scraped at all it will probably not cause any trouble in a tank like this. Wooden tanks will do, of course, but it would pay a packer who must use a tank here to throw out his wooden one and put in a tank such as is recommended above. It is hard to construct a wooden tank so that it will drain well; in fact, nine out of ten scarcely drain themselves at all; they are never kept as clean as they should be, and wet wood seems to be a favorite spot for molds to grow, so that frequent scrubbing is necessary if it is kept sanitary. It is most important to inspect the receiving tank carefully before it is first used in the morning, as they sometimes mold slightly over night, or dirt falls into them from overhead. A steam hose should be kept close to a wooden tank to sterilize it at night after it is scrubbed out. Finishing Whether or not a receiving tank is used, the finishing machine should be as close to the cooking kettles as possible, and should receive constant attention from a careful operator who can comprehend to some degree the importance of keeping it clean. If the filling department gets ahead of the cooking department and is obliged to wait fifteen minutes or a half hour for a fresh batch of pulp to come down, the man who tends to the finisher should take it apart at once, wash it off, steam it off thoroughly with the steam hose, and put it together again so that it will be clean and practically sterile when it receives the next batch. Otherwise the screen and the brushes will be clogged up with cold pulp when the fresh batch comes down, which is a bad condition, especially if the pulp is not to be sterilized after it is filled, which is usually the case with 5–gal. pulp. Even though the finisher is operated continuously through the day, it should be taken apart and cleaned at least twice during the morning and twice during the afternoon. The finishing machine should be operated slowly, so that the pumice will come out dry. The small receiving box under the finisher should drain completely so that it does not have a foot of cold pulp lying in it when the finisher is idle. Screen Metal for Finisher The best kind of screen for the finisher is made of monel metal. The brass screen is more common; however, the same thing can be had in monel metal, and it does not offer the opportunity for metallic contamination that the brass screen does. The monel metal screens wear very well and have proven themselves to be satisfactory in every respect. Aluminum should not be used, as it is eaten up by the tomato acid and will not last long. Effect of Finishing on Mold Count The opinion has often been expressed that the brushing of the pulp through the fine meshes of the screen breaks up the small clumps of mold and scatters them in small threads throughout the mass, thus increasing the mold count, since this count is not based on the total quantity of mold present, but upon the number of microscopic fields containing molds. Thus, by scattering the mold, instead of allowing it to be retained in comparatively large clumps, the number of microscopic fields containing mold threads would be increased. Although one might reasonably expect this to take place, experiments have proven that it does not take place. Several years ago, in order to determine this point, I analyzed thirty batches of catsup just before entering the finisher and again just after coming through the finisher. In every case the percentage of microscopic fields containing molds after finishing was practically the same as before finishing. A cone-shaped finisher with three revolving brushes and fine mesh screen was used for this test. Finishing Before Cooking Although the finishing machine, if properly tended to, is probably responsible for very little of the spoilage in pulp, it has been suggested to use the finisher before the pulp is condensed. Then the pulp can be drawn direct from the kettle to the cans, and the chance of contamination and cooling in the finisher can be eliminated. This idea is well worth experimenting with, as the pulp could be filled at almost the boiling point. I have not tried out this idea, but offer it here as a possibility which has advantages which are well worth looking into. Packers who are having spoilage trouble which they cannot attribute to other causes would do well to experiment with it. As to whether both the pulp machine and finisher would have to be used before the cooking, or whether the finisher alone would do, providing the tomatoes were previously crushed, or cooked in a “breaking tank,” would have to be determined by experiment. The method may be in use now by some packers; however, I have not heard of it being used. CHAPTER VI FILLING THE FINISHED PULP AND STORING THE CANNED PRODUCT Filling Devices for Five Gallons The most commonly used containers for pulp are the five-gallon can, the No. 10 and the No. 1 can. The usual method of filling 5–gal. cans is to draw the pulp from the finishing machine by means of a large, heavy wall, single line hose filling one can at a time. Some packers use a manifold by which five cans can be filled at once. This requires a lot of valves and enamel lined pipe fittings, and unless the operator is very expert the manifold will not do the work any faster than a single line hose. Square Can and Round Can The square 5–gal. can is preferred by nearly all packers to the round can. The round can is hard to handle, hard to stack, and is very wasteful of space wherever it is stacked. The square can is to be preferred in every way. Testing for Leaks When new cans are being used it shouldn’t be taken for granted that they are absolutely free from leaks, as it is sometimes found that a large percentage of a car of cans will run bad, and the packer should test representative samples from the car as soon as it is received, so that he can reject it and secure other cans if the car doesn’t test up right. The best way to do this testing is with a small tank of water, a one-eighth inch air line, giving about four pounds pressure, and a can tester. A simple kind of can tester can be easily constructed in any blacksmith shop, and merely consists of an iron brace to fit around the can and which can be quickly tightened over the can and released, and a soft rubber semi-circle to fit tightly into the cap hole and which is gripped at the top and held in place by one side of the brace. The one-eighth inch brass air pipe passes through the center of the rubber semi-circle and into the can. As soon as the can is tightly clamped and the cap hole sealed by the rubber, the air is turned on and the can is immersed in the water. The leaks show up very quickly under a four-pound pressure, and a dozen cans can be tested in as many minutes. Washing and Steaming New cans, as well as old ones, should be thoroughly washed and steamed before filling. There is often a fine, light colored dust in new cans which a good strong spray of water properly directed into the inverted cans will remove. Through the same pipe which directs the spray of water into the cans, the cans can be steamed by means of a simple arrangement of valves on the steam and water pipes. A washing and steaming rack can easily be fitted up which will wash and steam a half dozen cans at once. A single stream of water entering the cap hole of the inverted can is not sufficient to clean it. The pipe which enters the cap hole should be