HEAT IN THE PRESERVATION OF FOOD PRODUCTS 533 



The final heating of the food in the cans is more properly called 

 processing, a term which has long been in use by the commercial canner, 

 and under present methods of processing, the vacuum in the can appears 

 to be as essential to the preservation of the food as the heating itself. 



Conditions arising as a result of the World War have stimulated a 

 great deal of investigation by various workers to establish the tempera- 

 tures and length of time necessary for processing to secure actual 

 sterility of food products, this condition being very properly the ulti- 

 mate aim of the packer. 



SPECIFIC APPLICATION. For the preservation of fruit juices and 

 fermented products, pasteurization is much more extensively used 

 than processing at a higher temperature. If too high a temperature is 

 employed for fruit juices, certain compounds of agreeable taste and 

 aroma are destroyed, with a consequent deterioration in the flavor of 

 the product. Fruit juices may be sterilized by heating at a low tempera- 

 ture for a period of time on each of several successive days. 



The method of Appert has its widest application in the conservation of fruits, 

 vegetables, meats and fish. Whatever modifications are made in the handling of the 

 different classes of foods, the essentials are the same. The raw material, after 

 thorough cleaning and removal of waste if any, is filled into the cans and submitted 

 to the heating process, the degree of heat and time of processing varying with 

 different foods. With a few exceptions, notably asparagus, vegetables are im- 

 proved by heating above the boiling point. With fruits the reverse is true, the con- 

 servation of flavor being best at as low a temperature as is practicable to be employed 

 to properly preserve them from spoilage. Briefly the methods employed in canning 

 some foods follows: 



Meat. The canning of meat for interstate commerce is under Government 

 supervision. No meat may be used which has not undergone inspection, the plants 

 must comply with certain prescribed regulations, and the methods be approved. 

 This is the only line of canning under inspection. It practically limits the canning 

 of meat to the large slaughter houses, or to companies purchasing only inspected 

 products, and having inspectors in their plants. 



In the meat-canning industry, lean meat is largely selected for two reasons. 

 Fat, well-finished carcasses bring a better price when offered for sale in the fresh con- 

 dition; and in the second place, lean meat has a better appearance in the canned 

 state than fat meat. The selected meat is cut into pieces of approximately from 

 i to 4 pounds in weight, according to the size of the tins in whick it is to be pre- 

 served. The pieces are cut as nearly as practicable the same size, not only for pur- 

 poses of appearance in the cans when opened, but also that the heating process may 

 be more uniformly carried out. If the pieces were of different sizes, the smaller 

 ones would become thoroughly cooked and disintegrated before the larger ones were 

 sufficiently processed. 



