Fish

In fish, as well as in shell fish, a very large proportion of the food substances present is protein. This proportion varies with the quantity of water, bone, and refuse that the particular food contains, and with the physical structure of the food. In fresh fish, the percentage of this material varies from 6 to 17 per cent. The structure of fish is very similar to that of meat, as the flesh is composed of tiny hollow fibers containing extractives, in which are dissolved mineral salts and various other materials. The quantity of extractives found in these foods, however, is less than that found in meat. Fish extracts of any kind, such as clam juice, oyster juice, etc., are similar in their composition to any of the extractives of meat, differing only in the kind and proportions. In addition to the muscle fibers of fish, which are, of course, composed of protein, fish contains a small quantity of albumin, just as meat does. It is the protein material in fish, as well as in shell fish, that is responsible for its very rapid decomposition.

The percentage of fat in fish varies from less than 1 per cent. in some cases to a trifle more than 14 per cent. in others, but this high percentage is rare, as the average fish probably does not exceed from 3 to 6 or 7 per cent. of fat. This variation affects the total food value proportionately. The varieties of fish that contain the most fat deteriorate most rapidly and withstand transportation the least well, so that when these are secured in large quantities they are usually canned or preserved in some manner. Fish containing a large amount of fat, such as salmon, turbot, eel, herring, halibut, mackerel, mullet, butterfish, and lake trout, have a more moist quality than those which are without fat, such as cod.

Like meat, fish does not contain carbohydrate in any appreciable quantity. In fact, the small amount that is found in the tissue, and that compares to the glycogen found in animal tissues, is not present in sufficient quantities to merit consideration.

In fish, mineral matter is quite as prevalent as in meat. Through a notion that fish contains large proportions of phosphorus, and because this mineral is also present in the brain, the idea that fish is a brain food has become widespread. It has been determined, however, that this belief has no foundation.

The application of heat has the same effect on the protein of fish as it has on that of meat, fowl, and other animal tissues. Consequently, the same principles of cookery apply to both the retention and the extraction of flavor.