Soups made from meat require first the preparation of a special material called stock, a liquid foundation upon which to begin the soup.
Beef, veal, mutton, and poultry are all made into stock in the same manner, so that general rules for its preparation will be sufficient for all meat soups.
The principal constituents of meat and bones, the material from which stock is compounded, are fiber, albuminous elements, gelatinous substances, and flavoring matters. The albuminous elements are found only in the flesh. The gelatinous substance found in bones, skin, and tendons, is almost devoid of nutriment. In selecting material for stock, therefore, it is well to remember that the larger the proportion of lean meat used, the more nutritious will be the soup.
But little else than gelatine is obtained from the bones, and although serviceable in giving consistency, a soup made principally from bones is not valuable as a food. The amount of bone used for soup should never exceed the flesh material in weight. The bones, trimmings, and remnants of steaks, chops, and roasts may be advantageously utilized for soups. Bits of roast meat and roast gravies are especially serviceable material, since they are rich in the flavoring elements of meat. It should be remembered, however, that these flavoring matters are chiefly excrementitious or waste substances, derived from the venous blood of the animal.
The greatest care must be observed to keep the scraps perfectly sweet and fresh until needed, as stale meat is exceedingly unwholesome. If the scraps are mostly cooked meats and bones, a small portion of raw, lean meat should be used with them; it need not be of the choicest quality; tough, coarse meat, when fresh and good, can be advantageously used for soup stock.
If fresh material is to be procured, select for beef soups a piece from the shin or lower round; the same choice of pieces may be made of veal; of mutton, pieces from the forequarter and neck are best.
In preparing meat for soup, if it is soiled, scrub the outside thoroughly with a clean cloth wet in cold water, or cut away the soiled portion. Break the bones into as small pieces as convenient; cut the meat into inch dice, remove the marrow from the bones, and put it aside. If added to the stock, it will make it greasy.
Having selected proper material and prepared it for use, the next step is to extract the juices. To do this put it into cold water, bring very gradually to the boiling point,—an hour is not too long for this,—then cook slowly but continuously. In the observation of these simple measures lies the secret of success in stock-making.
The albuminous elements of the meat, which are similar in character to the white of an egg, are readily dissolved in cold or tepid water, but boiling water coagulates them. If the meat is put into boiling water, the albumen coagulates, or hardens, forming a sort of crust on the outside of the meat, which prevents the inner juices from escaping; on the contrary, if the meat is put to cook in cold water, and is gradually raised to the boiling point, the soaking and simmering will easily extract and dissolve the juices.
Salt likewise hinders the extraction of the meat juices, and should not be added to stock during its preparation.