BOILING
The term "boiling," as applied to cookery, means cooking in a boiling liquid. Many kinds of food need the action of water or other liquid, combined with heat, to cook them in the best manner, and boiling is one of the most common forms of cookery. When water becomes too hot to bear the hand in it with comfort, it has reached one hundred and fifty degrees, or the scalding point. When there is a gentle tremor or undulation on the surface, one hundred and eighty degrees, or the simmering point, is reached. When there is quite a commotion on the surface of the water, and the bubbles breaking above it throw off steam or watery vapor, two hundred and twelve degrees, or the boiling point, is reached. After water reaches the boiling point it becomes no hotter, no matter how violently it may boil. The excess of heat escapes in the steam. This important fact is rarely understood by the average cook, and much fuel is often needlessly wasted because of the mistaken idea that rapidly boiling water cooks food more quickly.
In all ordinary cooking, simmering is more effective than violent boiling. The temperature of the water may be slightly raised by covering the kettle. If sugar or salt or anything to increase its density, is added to water, it takes longer for it to boil, but its boiling temperature is higher. This explains why boiling sugar syrup and boiling salt water are hotter than boiling fresh water. Boiling effects partial destruction or removal of organic and mineral impurities found in water, hence the importance of boiling the water where such impurities exist. Boiling also expels all the air and the gases which give fresh water its sparkle and vitality. Therefore, the sooner water is used after it begins to boil, the more satisfactory will be the cooking.
Fresh water should be used when the object is to extract the flavor, or soluble parts, as in soups and broths. Salt water should be used when it is desired to retain the flavor and soluble parts, as in most green vegetables. Cold water draws out the starch of vegetables. Boiling water bursts starch grains, and is absorbed by the swelling starch, and softens the cellulose in cereals and vegetables.