FOOD PROTEINS 275 



well as differences from the methods used for preserving 

 hides and skins (Part I., Section I., p. 12). The curing 

 of hides and skins is a temporary preservation from putre- 

 faction until the opportunity is convenient for the permanent 

 preservation (i.e. tannage). The preservation of meats is 

 analogous to curing inasmuch as more drastic treatment 

 might indeed make them non-putrescible, but would also 

 render them indigestible and unsuitable for food. Thus 

 drying, salting, drying and salting, pickling and freezing, are 

 just as suitable for preserving food proteins as for hide and 

 skin proteins. Hence we have dried meats, salt bacon, 

 pickled beef, frozen mutton, etc. To a limited extent 

 smoking (fish, bacon, etc.) has been employed as a cure. 

 When it has been applied to skins it is usually combined 

 with a fat tannage. There is, however, one method of 

 preservation of proteins, inapplicable to skins, which has 

 been eminently successful and useful for food proteins, 

 viz. sterilization by boiling. The food has been placed in 

 tins, hermetically sealed, and thoroughly sterilized. Hence 

 have appeared corned beef, tinned tongue, sardines, etc., 

 which merely illustrate the immense possibilities involved. 

 A noteworthy advantage of this method of preserving 

 animal food proteins, is that the food is already cooked and 

 prepared for immediate consumption. 



Another line of effort is the preparation of concentrated 

 foods. Just as animal foods are on the whole more concen- 

 trated in protein than vegetable foods, so these prepared 

 animal foods are more concentrated than animal flesh, and 

 generally also more soluble. Such preparations of animal 

 protein are obviously useful when there is difficulty in 

 swallowing and when journeys are necessary into regions 

 of poor food supply. It is a little doubtful, one must say, 

 whether the concentration is as great in some cases as is 

 claimed. 



Yet another industry based upon the animal proteins is 

 the manufacture of meat-extracts. These are not merely 

 concentrated extracts of animal flesh, but contain especially 

 the stimulative properties of animal food proteins. There 



