There is an erroneous impression that articles cook faster when the water is boiling violently, but this is not the case; the ebullition is caused by the escaping steam, which is lost heat, and the water at this time is at 212° (except in high elevations), however fast or slow it may be boiling. If, however, a little sugar or salt is added to the water it increases its density, and the heat rises to 224° before the steam escapes. The heat can be raised also by covering the pot and confining as much of the steam as possible. Where violently boiling water is recommended, as for rice and green peas, the object is not greater heat, but to keep the grains and peas separated by the turbulence of the water. There is waste of fuel in unnecessarily fast boiling, and economy can be easily practised here, especially where gas is used, as the boiling point, once reached, can be maintained with but little heat. Where the juices and color are to be retained, the articles are put into already boiling salted water. The albumen on the surface is then at once coagulated and the juices shut in. Where the object is to extract the juices, as for soups, they must be cut into pieces so as to expose more surface, and put into cold water, and the heat of the water gradually raised to the simmering point only. The slow, long cooking obtained in simmering water best destroys the fiber of meat, and tough pieces cooked in this way are made tender. To render tough pieces tender, the meat is first put into boiling water in order to fix the albumen on the surface, the heat then reduced, and the cooking done at the simmering point, which is 185°. Hence, water at different stages of heat is used, according to the object in view, and the result is as definite as that of the different degrees of heat in an oven, so this point should not be considered as of little importance.
The flavor of meats and vegetables is volatile, and much of it can be carried off by escaping steam, as is demonstrated by the odors which sometimes pervade the house. To prevent the latter, and also to make the article tender and retain all its flavor, the pot should be covered and the water kept at the simmering point only.
An exception to this rule is made in the cases of cabbage and cauliflower. These strong-flavored vegetables will be much less objectionable when cooked in rapidly boiling water in open vessels (see page 212). Green vegetables should be boiled in open vessels, as high heat destroys their color. AU meats should be well tied and skewered, to keep them in good shape while boiling, and, when possible, be placed with the bone side up, so if any scum settles it will not spoil the appearance of the dish. For fish a little vinegar should be put into the water, as it hardens the meat and helps to prevent its falling apart (see page 113).
Salt water is used where the object is to keep the flavors in, fresh water where it is to draw them out as in soup, where the salt is not added until the cooking is completed. The rule of not piercing meat, thus letting out its juices, applies to boiling as well as to other methods of cooking. Fifteen minutes to the pound is the rule for mutton or tender meat, a much longer or indefinite time for tough meat.
Ham is done when the skin peels off easily.
The scum should be taken off the pot when boiling meat.
Milk boils at 196° and easily burns, therefore it is safer to use a double boiler for anything containing milk. When using a double boiler, the liquid in the inner pan is scalded when the water in the outside vessel boils.