The term animal food is popularly used to denote the flesh of animals, birds, and fish only, though it ought also to include soups (made from meat or bones), beef extracts, beef-teas, beef juices, jellies, i.e. food prepared from gelatine; milk, with its derivatives of cream, butter, skimmed milk, cheese; and eggs.
The flesh of animals comprises muscle with the connective tissue, fat, nerves, and bloodvessels supplying the muscle. Microscopic examination shows the muscle to be made up of fibres. The length of the fibre varies in different varieties of animal flesh; e.g., very short fibres are present in the breast of a chicken, and very long fibres in the limbs. For this reason the former are more easily digested.
The fibres are held together by connective tissue; this connective tissue yields gelatine on boiling. The amount of connective tissue is proportionate to the age of the animal, being large in amount in old animals. Everyone is familiar with the difference between a chicken and an old hen; the latter, however, makes better soup.
In young animals the muscles are not fully formed, and are more watery, so that young meat (lamb and veal) loses half to three-quarters of its weight in cooking; the muscle albumin is replaced by gelatine-forming substances, and the fats and salts are also smaller in amount. Veal is known to be very indigestible to some people, but it is useful for making soup, as the protein-forming gelatine, on boiling, produces good jelly stock.
The best beef is obtained from a two-year-old ox, and the best mutton from a two-year-old sheep. In addition to being more digestible, the flesh of full-grown animals is richer in extractives and has more flavour than the flesh of an immature animal; this explains why lamb is eaten with mint sauce and veal with mixed herbs.
The influence of feeding, on the flavour of the flesh, is illustrated in the difference between the flavour of mutton from hill-fed sheep and from sheep fed on turnips. Wild rabbits are much more palatable than tame ones, probably on account of the aromatic herbs, such as thyme, in their diet. Seabirds have a fishy flavour, and are not easily digested.
The chemical composition of the meat is greatly influenced by the breed, the condition, and general health of the animal, i.e., the degree to which the animal has been fattened, and also by the particular part from which the cut is made. The flank contains 43 per cent, of water, and the round of beef 60 per cent, (see fig., p. 52).
The average composition of meat is given in the following table: -
Lean . • .
Medium . . .
Note the relationship between water and fat - the less water the more fat. Fattening, therefore, represents an absolute gain of nutritive value, and not a replacement of nitrogenous matter by fat.
(More economical than the English mode).
Explanation of diagram of the usual Scotch mode of cutting-up an ox: - I A. Cheek.
IB. Chip, generally used for hare-soup. 2. Neck, used for soups, stews. 3 and 4. Spare ribs, generally roasted; sometimes stewed.
5. The ribs, roasted; sometimes boned, rolled, and salted.
6. First runner. This is cut close by the shoulder-bone, and is used for boiling or stewing. 7 and 8. Also runners. These two are sometimes divided across by the dotted line, and the fleshy end (next the head) used for stewing, boiling, or beefsteak pie, and the thin end salted. Sometimes only two runners are cut, sometimes only one.
9. Nine holes, used chiefly for pickling, sometimes for plain boiling or stewing; not so fat as the brisket.
10. Brisket, stewed or corned.
11. Marrow bone.
12. Hough or shin, used for soup; the fleshy end is good for stewing.
13. Sirloin, cut generally into three parts, called the double side, middle cut (or Scotch and English), and the thin end.
14. Thin flank, used for boiling; often salted.
15. Thick flank or fleshy end of heuck-bone, used for stewing steak, or salted and rolled, also for pies; no bone in it.
16. Heuck-bone, best for gridiron steak.
17. Rump, generally boned and salted; sometimes stewed with the bone in, or boiled. It is used in France for pot-au-feu.
18. The round. This weighs about 30 to 40 lbs.; the upper part is sometimes cut into steaks. Sometimes the whole is cut into two rounds; a thick flap of fat, called the shaugh, is left to roll round the bare side of the bone.
19. Used for mince, stew, or beef-tea.
The nitrogenous part of flesh consists chiefly of the following proteins: Myosin, muscle albumin, and haemoglobin. Myosin coagulates after death, this condition being known as rigor mortis. Meat in this state is tough and indigestible; on this account meat should either be eaten immediately after killing, before rigor mortis has had time to supervene, or it should hang until the stiffening has passed off. In hot climates, where decomposition sets in rapidly, flesh is cooked immediately on being killed. The disappearance of rigor is due to sarcolactic acid being formed, and the transformation of the myosin into an acid albumin. Whenever the rigor mortis is over, the flesh begins to decompose slowly, and this incipient decomposition makes it more tender and better flavoured for a time.
The serum albumin of muscle is one of the most soluble of the muscle proteins, and this albumin can be extracted by water; and this extract, amounting to 5 or 6 per cent., represents the maximum strength of an aqueous extract of beef-tea. The remaining 14 or 15 per cent, of proteins are insoluble in water, though dissolved by the digestive juices.
The extractives in meat are substances which can be extracted by boiling water. They have no direct nutritive value, but are important since they impart the characteristic flavour to meat. These are more fully considered in the section on beef-teas and extracts on p. 75.
Fat is embedded in the connective tissue between the fibres in mutton and beef. Fat is almost entirely absent in game, and in the breast of chicken, and in most varieties of white fish. In pork, duck, goose, herring, mackerel, and salmon the fat is abundant. The fat seems to lessen the digestibility of the meat, possibly by forming a coating round the fibres.
Meat should be cut or carved at right angles to the long axis of the fibre. It is then more easily chewed, the flavour is better, and the digestive juices reach the fibres more easily.
The acids which develop in meat while hanging improve the flavour, and also help to increase the digestibility. This effect can be brought about by various devices, such as the addition of vinegar to boiling meat, the rubbing over veal with lemon juice before frying or stewing, and by eating vinegar with crab and lobster.