The object of cooking is to make food more digestible and more attractive. For changes occur in food when it is subjected to heat which make it more easily used by the body and which make it more agreeable in flavour—more "appetizing." An incidental but important benefit from cooking is that great heat kills the animal organisms which food sometimes contains.
1. THE PROCESSES
The most usual processes of cooking are broiling, boiling, stewing, braising, frying, roasting and baking.
Broiling.—Food is broiled by being held close to a fire of glowing red coals. The utensil needed for doing this is a wire broiler, which should be greased before the meat is laid in it, preferably with a bit of fat from the meat. In broiling, the chief object is to keep the juices of the meat from running out. For this reason the meat is laid close over the red coals for about ten seconds, then turned with the other side to the coals that both may be seared almost at once. Afterward it is turned frequently to prevent burning. Broiled meat is not seasoned until it is done because salt draws out its juices. Care is also taken not to cut or pierce the meat while it is cooking.
Steaks and chops are almost always broiled; fish, chicken and oysters are frequently cooked in this way.
Broiling may be done in a frying pan heated intensely hot, and greased as the wires of the broiler were with a bit of fat from the meat—a tiny bit. The meat is laid in the pan, first on one side for a few seconds, then on the other. It is turned, as when broiling over the coals, often enough to keep it from burning.
Articles of food which are thin need a hotter fire, or to be laid nearer the fire than thicker ones. This assures that the time required to brown the outside will be too brief to dry the article through and through.
A thick piece of meat will not cook through to the middle for some time and should therefore be exposed to a slower fire that the outside may not be hard before the inside is cooked. These principles apply also to the roasting and baking of thick and thin articles of food.
Boiling.—As only liquids can boil, we mean when we say we boil potatoes, that we cook them in boiling water. When water is heated, tiny bubbles of steam rise in it, which at first break before they reach the surface; this is "simmering." As the heat increases, the bubbles rise more quickly and higher, and break at the surface; this is boiling. Water boils at 212° F., and, though its motion may be increased by heat to a "gallop," it gets no hotter, for the steam escapes when the little bubbles burst. Liquids which have a greater density than water, such as salt water, syrup, grease and oil, do not boil until they have reached a higher temperature than 212°. Milk boils at a lower temperature than water. The reason it "boils over" so easily is that what one might call the texture of the milk bubbles which enclose the steam is less delicate than that of the water bubbles, therefore instead of breaking when they come to the surface, they pile up one upon another.
Boiling water hardens and toughens some of the protein substances in food, but softens and makes digestible most of the substances included under the head of carbohydrates.