School and Home Cooking

by Carlotta C. Greer

ENERGY-GIVING AND BODY-BUILDING FOODS,—RICH IN PROTEIN

LESSON XLII

EGGS [Footnote 44: NOTE TO THE TEACHER.—If the egg lessons came in the mid-winter months, they may be omitted until the price of eggs is reasonable; or the "theory" concerning eggs and the experiment concerning the temperature of cooking protein-rich foods may be given, and the cooking of eggs take place later in the year.]

PROTEIN, A BODY-BUILDER AND REPAIRER.—An automobile requires not only fuels for its use but occasional repair. The body also needs not only fuel but building and repairing materials. The function of the fuel foods considered thus far is to give energy to the body. But there is another great class of foods, or foodstuffs—those included under the term protein—that not only give energy to the body but also build up or promote growth and repair it or support life. The process of building and repairing takes place in the body cells. Hence the body differs from an automobile in that it possesses the property of self-building and repairing.

The child must have protein food so that it can grow and live when growth is completed, the adult must have protein food so that it can live and maintain health. The slightest using of the body causes the wearing away of some of the tissues, hence the importance of food containing the foodstuff, protein.

Protein is a very broad term, including many different materials, having different properties. Some proteins will promote the growth of the body and support life, while others are growth promoting but not life supporting, while still others are only life supporting.

The first type of protein is sometimes called complete protein, while the two latter types are called incomplete protein. In food study and meal planning, it is not sufficient to know that a food contains protein; one should know whether the protein is complete or incomplete. The incomplete proteins need to be supplemented with other foods containing the lacking type of protein. Milk, eggs, cheese, meat, and fish contain complete proteins, while beans, peas, gelatine, and certain cereals contain incomplete proteins.

A consideration of eggs, a food rich in complete protein, follows:

EXPERIMENT 37: THE COAGULATION OF EGG WHITE.—Put the white of an egg in a dish and break the membranes by cutting with a pair of scissors. Then place a small quantity of the white of egg in a test tube. Apply heat. Into what form is the liquid egg white changed by heat?

When eggs are cooked, the protein in the white called albumin stiffens or coagulates. The yolk also contains a kind of protein which coagulates when heated.