Methods of Cooking Meat.—Roasting, baking, boiling, stewing, braising, frying and grilling are the usual methods of cooking animal food. To explain the philosophy of these simple operations, we must notice the effects that are produced by heat on the principal constitutents of flesh. When finely chopped, mutton or beef is soaked for some time in a small quantity of water, and then subjected to slight pressure, the juice of the meat is extracted, and there is left a white, tasteless residue, consisting chiefly of muscular fibre. When this residue is heated to between 180° and 200° F., the fibres shrink together, and become hard and horny. The influence of a higher temperature on the soluble extracts is not less remarkable. When the watery infusion which contains the nutritive constituents of the meat is gradually heated, it soon becomes turbid, and, when the temperature reaches about 160°, flakes of whitish matter separate. These flakes are ALBUMIN, a substance precisely similar in all its properties to the white of egg. When the temperature of the watery extract is raised to 158°, the colouring matter of the blood coagulates, and the liquid, which was originally tinged red by this substance, is left perfectly clear, and almost colourless. When evaporated, even at a gentle heat, this residual liquid gradually becomes brown, and acquires the flavour of roast meat. The fibres of meat are surrounded by a liquid which contains albumin in its soluble state, just as it exists in the unboiled egg. During the operation of boiling or roasting this substance coagulates. The tenderness of well-cooked meat is consequently proportioned to the amount of heat employed, and the slight or complete coagulation of the albumin deposited in its substance. Meat is done when it has been heated throughout only to the temperature of coagulating albumin, provided the heat is continued long enough; it is thoroughly done when it has been heated through its whole mass to the temperature at which the colouring matter of the blood coagulates; it is overdone when the heat has been continued long enough to harden the fibres.
During the operations of Boiling, Roasting and Baking, fresh beef and mutton, when moderately fat, according to Johnston, lose, on an average about:—
|In Boiling.||In Baking.||In Roasting.|
|4 lb. of beef lose||1 lb.||1 lb. 3 ozs.||1 lb. 5 ozs.|
|4 lb. of mutton lose||14 ozs.||1 lb. 4 ozs.||1 lb. 6 ozs.|
More recent experiments also show that animal matter loses more weight by roasting than by boiling. In roasting, the loss arises from the melting out of the fat and evaporation of water; but the nutritious matter remains condensed in the cooked meat, whereas, in boiling, the gelatin is partly abstracted. Roast meats are therefore more nutritious than boiled meats; but in consequence of the chemical decomposition of the fat of roast meats, due to a long continued exposure to an intense heat, they are less easily digested.