HEAT IN THE PRESERVATION OF FOOD PRODUCTS. 389 



From the character of the flora, fruits as a rule require a comparatively low temperature 

 for sterilization, while some vegetables and meats require a very high temperature 

 to destroy the bacterial spores sure to be present. Briefly, the methods employed in 

 canning some foods follow: 



Meat. 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 condi- 

 tion; 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 which it is to be preserved. The 

 pieces are cut as nearly as practicable the same size, not only for purposes of appearance 

 in the cans when opened, but also that the process of sterilization may be more uniformly 

 carried out. If the pieces were of different size, the smaller ones would become 

 thoroughly cooked and disintegrated before the larger ones were sterilized. 



After the pieces have been selected and dressed they are parboiled before being 

 placed in the containers, the time ranging from eight to twenty minutes, according to 

 the size of the pieces of meat. The object of parboiling is to secure the shrinkage which 

 always takes place on heating. Meats put into tins in the fresh state and sterilized 

 shrink to about two-thirds of their original volume. When the meat is put directly into 

 boiling water, there is less loss of protein than when the meat is placed in cold water 

 and heated gradually. During parboiling, the meat loses about i per cent of the 

 protein content, about one-third of the total meat bases, and 50 per cent of the 

 mineral matter. 



This shrinkage by parboiling tends to make a more concentrated article, thus 

 favoring transportation, and, pound for pound, the nutritive value is not lowered. 

 Practically, the nutritive value of a pound of properly canned beef is about one-third 

 greater than that of i pound of fresh beef of the same kind. After parboiling, the 

 meat is placed in tins, by hand or by machinery, and to each can is added a small 

 quantity of "soup liquor," the manner of preparation of which is not disclosed by the 

 packers. It may be regarded as a thin soup, the object of which is to fill up the spaces 

 between the meat, and to add condimental substance to render the meat more palatable. 



After the cans are filled, they are closed and processed in suitable retorts by steam 

 under pressure, as previously described, the temperature ranging from 110 to 120. 



A modification of the usual method consists in exhausting the cans in vacuo, and 

 automatically sealing them in the exhausted state, thus removing all the air and other 

 gases, after which they are placed on an endless conveyor and dipped into an oil bath at 

 a temperature of 115, the speed of the conveyor being so regulated that the cans remain in 

 the bath a sufficient length of time to complete sterilization before they are carried out 

 at the opposite end. They are next carried automatically into a solution of carbonate of 

 soda, and finally into pure water, after which they are dried, painted with a shellac or 

 lacquer and labelled. 



Fresh meats other than beef or pork are canned in a fresh state. Game and wild fowl, 

 as well as domesticated chickens, ducks, geese, turkeys, and pigeons are used, the general 

 process being as already described. Horse meat is used more or less commonly in some 

 European countries, but probably rarely in the United States. 



Fish. The process of fish canning does not differ materially from that of other 

 meats. On account of its proneness to rapid decomposition, especial care must be 



