When a crusher is used it takes the place of the cyclone or pulp machine, although it performs an entirely different kind of an operation, and the tomatoes go through exactly the same process as in cold pulping, except that instead of removing the seeds and skins from the tomatoes before cooking, the tomatoes are chopped very fine and conveyed to the cooking kettles—seeds, skin and all. It is obviously somewhat harder to gauge the finishing point of a batch of pulp where the skins and seeds are present, however a little practice largely eliminates this difficulty, and there is always the method of determining the specific gravity by weight to fall back on. The seeds and skins will not interfere with making the specific gravity test as it is usually carried out in the cook room with a large copper flask, small trip balance, and set of weights.
Conveying to Kettle
If the plant is so arranged that the pulped or crushed tomatoes can be conveyed to the cooking kettles by gravity, that is an advantage, as it does away with a pump and someone to tend to it, and the fewer the pumps, the better; however, in most plants it is necessary to pump the pulped or crushed stock into the cooking kettles. Unless the plant consists of several floors and the tomatoes start at the top and come out as finished pulp at the bottom, or the plant is built on a terraced plan, as one plant is in Indiana, which is built on the side of a hill, it is necessary to do a certain amount of pumping. An ordinary pump will not do, as there would be contamination by iron, and considerable rusting, while the pump was idle, of those parts of the pump with which tomato juice comes in contact, this rust to be carried along with the tomato juice the first time the pump is used again. The rotary pump constructed partly of bronze or nickel is very good for this purpose, and offers as little opportunity for metallic contamination as any pump does.
The pipe used for the conveying of this tomato stock should by all means be enamel lined. Enamel lined pipe, if properly made, will last for many years without chipping or cracking. Just how long it will last on the average I cannot say, but I have often taken down lines of enamel lined pipe that have been in use for several years, and it looked practically as good as new. The flanged pipe with flanged fittings is better than that with the ordinary screw ends, as it makes practically a continuous white tube without any pipe threads in which molds, yeasts, and bacteria can lodge and multiply.
Wooden troughs are still used in many plants for conveying tomato juice and pulp, but they are a relic of the old days, and have no place in the modern pulp or catsup plant. Wooden troughs are hard to keep clean, they mold very quickly after they become damp, they are open to contamination from ceilings and roofs which aren’t always in good condition, and they are usually wasteful. It will pay any packer who still uses even a few wooden troughs to invest in enamel lined pipe. Wooden pipe is also unsanitary for this purpose, as mold grows in it and clings so tightly to the porous, damp surface that it cannot possibly be flushed out.
Value of Pumice
This chapter, which deals principally with cycloning, seems to be a fitting place to discuss the value of the pumice which comes as a waste product from the cyclone. Although it has been repeatedly demonstrated by chemical analysis that this pumice or tomato waste is a valuable by-product, every time the question has come up of its utilization and preparation into a salable product or products, the decision has been that the expense involved would be too great to make it pay. This by-product is profitably handled in Italy, producing an oil of commercial value, and an oil cake which is used for stock feed; however, the conditions in Italy and in this country are very different. In the Parma district of Italy there are forty factories very close together, and little expense is involved in bringing the waste to a central point where enough of it can be had to keep a drying outfit and an oil press or oil extraction outfit busy. Labor is also very cheap and plentiful, and there is a ready market for the product, the oil being used as a soap stock, and the oil cake finding ready sale as a stock feed. In this country, however, there is not enough waste at even one of the largest plants to pay for the operation of a drying outfit and the pulp plants are so scattered that hauling or shipping charges to a central point would be expensive. Furthermore, labor is scarce and expensive.
That quite a little labor is involved in the preparation of the waste is soon discovered by a little experimenting. As the waste ferments quickly it must be handled as produced, or preserved in some way, which would be a questionable operation, as the oil cake is used for stock feed. As the skins are practically valueless, they must be separated from the seeds in which all the value lies. This separation can either be carried out in the moist state by a gravity separation in water, in which the seeds, being heavy, sink, and the skins float; or by the use of a fanning mill after drying, in which case the dried skins, being very light, are blown out. Before drying either the seeds alone or the unseparated waste, the excess moisture must be pressed out with a hydraulic press. The pressed product must then be broken up and put through a steam or hot air dryer of the rotary, cylindrical type. After the seeds are dried to a 10 per cent moisture basis they must then be ground, and the oil extracted either by pressure, or by dissolving it out with a chemical agent, such as carbon tetrachloride. The oil cake which remains would then be sacked for stock feed.
This briefly gives an idea of the labor involved, and the difficulties surrounding the situation. It may be successfully worked out some time, but will require close co-operation from a number of large pulp plants which are near each other to be a success. Some plants are giving the waste to farmers if they will haul it away, and I know of one farmer who has for years fattened a bunch of hogs cheaply during the tomato season in this way. It is a queer thing, though, that most farmers turn up their noses at the idea.
The seed, when dried to a 10 per cent moisture basis, contains about 23 per cent protein and from 20 to 25 per cent of fat. After the fat is extracted the protein in the cake will run close to 30 per cent.