Tomato Products

Tomato juice and tomato concentrate are more recent examples of biologically stable products and are ideal candidates for preserving. The tomato harvesting season is relatively short, the crop is huge in size, the demand for tomato products in formulated foods was growing rapidly, and nearly all the tomatoes for processing are mechanically harvested. Mechanical harvesting is an economic necessity, but it does result in more mechanical damage to the crop than the old-fashioned hand harvesting. This means that the crop must be processed as soon after har vesting as possible. Minimal processing to produce a biologically stable intermediate is a virtual necessity to minimize the costs of production and ensure a high-quality product.

Biogically stable intermediate products became feasible with the concept of aseptic packaging developed by W. M. Martin in 1935 (4). He developed the concept of sterilizing a product, sterilizing the container, and bringing the two together, with a sterile cap, in a sterile atmosphere. Conventional canning at that time consisted of filling and capping a container and heat treating the closed container to ensure sterility. This means that the center point of the container needed to receive sufficient heat treatment to ensure sterility; however, the outer portions of the container would be overheated and the quality of the food would be lowered. This effectively limited the size of the container to a No. 10 can, approximately 1 gal. If the product could be sterilized in a thin film outside the container, and packaged aseptically, the size of the container was limitless. I remember visiting a large food processor in the 1940s. They required a large quantity of tomato paste to formulate into products like pork and beans, soup, pizza sauce, sardines in tomato sauce, barbecue sauce, and many others. During the tomato season they would pack their year's quota of tomato juice, tomato ketchup, and tomato soup and make the remainder into tomato concentrate or paste. The concentrate would be filled into No. 10 cans, capped, and stored in a huge warehouse. The concentration process would make the puree essentially sterile, and the hot fill would sterilize the cans and lids. This process worked very well, but it was labor intensive and it was not perfect. Some of the cans leaked, and one leaky can makes quite a mess.

Bulk storage of tomato juice in the United States started essentially with the work of Nelson at Purdue University (5-7). He experimented with aseptic storage of tomato juice in tanks up to 100,000 gal, and even larger, and now numerous large storage systems are in place worldwide. The concept is simple, but the implementation is more complicated. Tomatoes can be mechanically harvested into large containers and brought immediately to the factory for processing. After washing, the tomatoes are chopped and screened to remove skins and seeds and pumped to a heat exchanger that sterilizes the juice. A number of systems are available to sterilize the juice, but nearly all employ highly efficient heat exchangers that use the high temperature/short time (HTST) or the ultrahigh temperature (UHT) approach to deliver a quantity of heat lethal to microorganisms. The short heating time ensures maximum retention of nutrients and flavor. A deaeration system is necessary to remove dissolved air in order to minimize loss of quality during subsequent storage. Large tanks are sterilized with hot water and chlorine, and the juice is pumped into them. The whole system, including the pumps, pressure reduction valves, heat exchangers, and the valve system, is closed and operated aseptically, which ensures that sterile air enters the tank to replace the product that is removed on demand for later formulation. The tanks can be refrigerated with interior coils or simply stored in a refrigerated building, if desired, depending on the quality demands of the final product. The tanks can also be mounted on a rail car or truck for shipment to any area. The same system can be operated with tomato concentrate, depending on the requirements of the formulator.

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