Page:Food and cookery for the sick and convalescent.djvu/74

44 care, while baking requires good judgment, coupled with experience. In the many cook books, various oven tests are suggested, and oven thermometers have been placed upon the market, but all are of but little practical value, as one must gain this knowledge by her own experience.

Vegetable foods abound in starch. Cold water separates starch grains; boiling water causes them to swell and burst.

Experiment 1. Mix two tablespoons flour with one-third cup cold water, and let stand five minutes. Flour settles to bottom of vessel.

Experiment 2. Stir mixture and heat to boiling point. Starch grains swell and burst, making a paste.

Dry heat, at a temperature of 320° F., changes starch to dextrine, which is soluble in cold water. Examples: Crust of bread and baked potato.

In cooking vegetables the object is to soften cellulose as well as swell and burst starch grains, and this is best accomplished by keeping the water at the boiling point throughout the entire cooking. By the proper cooking of starchy foods their digestibility is greatly increased.

Albumen is the principal constituent of white of egg. It is dissolved in cold water, and coagulated by heat at a temperature of 134° to 160° F.

Experiment 1. Put white of egg in cold water, stir, and albumen is dissolved.

Experiment 2. Put white of egg in cold water, heat gradually to boiling point, and albumen coagulates.

One of the proteids of meat is albumen, some of which is soluble in cold water and coagulated by heat.

Experiment 1. Cut beef in small pieces, put in cold water, and let stand twenty minutes. Water of a reddish color.

Experiment 2. Heat to boiling point and dissolved albumen will be coagulated.

Experiment 3. Cut beef in small pieces and plunge into boiling water. Albumen will be coagulated quickly, thus preventing its escape.