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.

EXPERIMENT 38: THE SOLUBILITY OF ALBUMIN.—Put a small portion of the broken egg white in a test tube. Half fill the tube with cold water. Then turn the contents of the tube on to a folded filter paper, and catch the filtrate in another test tube. Are the contents of the tube clear?

Apply heat to the filtrate. What happens? Does this prove that egg albumin was dissolved in the water before applying heat to the contents of the tube? Explain.

EXPERIMENT 39: TEMPERATURE AT WHICH EGGS COAGULATE.—Place a teaspoonful of white of egg in a test tube. Insert a thermometer in the test tube and place the test tube in a beaker of water (see Figure 39). Heat the water gradually. Note and record: (a) Temperature at which coagulation first appears. (b) Temperature at which the egg white is entirely coagulated. Has the water reached the boiling point when the egg white has entirely coagulated? What application can you draw from this as to the temperature of the water in which eggs may be cooked?

EXPERIMENT 40: COMPARISON OF COOKED AND BOILED EGGS.—Remove at once about half of the coagulated egg from the test tube of Experiment 39. Examine it and press it between the fingers.

Continue to heat the remainder of the egg in the test tube, allowing the water to boil a few minutes. Then remove the egg, examine it, and press it between the fingers. Compare it with the egg cooked below the boiling point of water. Which is more tender? Which breaks more easily? Which do you consider more palatable? What conclusion can you draw concerning the temperature at which eggs should be cooked to make them most tender and palatable?

DIGESTIBILITY AND PALATABILITY OF EGGS.—The experiments of this lesson show that eggs cooked at simmering temperature are more tender than those cooked at boiling temperature. The question may arise, is the tender egg more wholesome than the tough egg? It is true that eggs cooked below the boiling temperature will digest in a little less time than those cooked in boiling water. Since, however, the tougher egg is as completely digested as the more tender, the difference in the time of digestion is a matter of little importance.

[Illustration: FIGURE 39.—APPARATUS TO DETERMINE THE TEMPERATURE AT WHICH
EGGS COAGULATE.]

But even though the difference in digestion is not considered, the difference in palatability is worth some attention. If soft-cooked and soft-boiled eggs are compared, the soft-cooked will be found to be much more uniformly cooked. The white of a soft-boiled egg may be firm, while its yolk is very soft or the white may be soft while its yolk is raw.

STRUCTURE OF EGGS.—A hen's egg consists of shell, membrane, white, yolk, and the little mass in the yolk called the embryo, from which the young chicken grows. The yolk is kept in place by two twisted cords of white membrane. This membrane is the first part to disappear when the egg begins to spoil.

CARE AND USE OF EGGS.—(a) Wash eggs just before using. [Footnote 45: Washing removes a coating on egg-shells. This coating prevents the entrance of microorganisms. Hence eggs should not be washed until they are to be used.] The shells may be used for clearing coffee.

(b) Keep eggs in a cool place.

(c) The unbroken yolk of an egg may be kept from hardening by covering with cold water.

(d) All protein-rich foods contain substances which spoil or decompose readily. The egg loses water by evaporation through the pores in the shell; air enters to take the place of this and since the air contains microorganisms, the egg spoils. Eggs may be kept fresh by keeping air out of them. They may be preserved by packing them, small end down, in bran, sawdust, or sand; by immersing them in water-glass.

(e) When using several eggs, if not sure of their freshness, break each separately into a saucer and examine before adding to the rest.

(f) When using a number of eggs, it is well to scrape out the bit of white clinging to the inside of the shell.

TESTS FOR FRESHNESS.—(a) A fresh egg has a rough shell. (b) Drop an egg into cold water. If it sinks, it is fresh; if it floats, it is stale.

SOFT-COOKED EGGS

Place eggs in enough boiling water to cover. Remove from the fire, cover, and allow to stand from 5 to 8 minutes.

The time of soft-cooking an egg varies with the different conditions. The time depends upon:

(a) Temperature of the eggs.

(b) Number of eggs cooked.

(c) Quantity of water used.

(d) Place on the stove.

One must determine by experience the length of time of cooking to produce the desired results.

By following the method above, eggs may be cooked at the dining table.

HARD-COOKED EGGS. [Footnote 46: NOTE TO THE TEACHER.—The Hard-cooked Eggs prepared in this lesson may be used in the preparation of Goldenrod Eggs of the following lesson.]—Place eggs in cold water and heat the water gradually until it reaches the boiling point. Remove from the fire at once; cover and place on the back of range, or in a warm place, for 20 minutes. Plunge into cold water, so that the shells may be removed easily.

Eggs may be hard-cooked by using the same method as for soft-cooked, allowing the eggs to remain in the hot water for 40 minutes or longer.

Eggs may also be hard-cooked in the double boiler. Put boiling water in the top and bottom of the double boiler. Place the eggs in the top part and cook 40 minutes.

If hard-cooked eggs are not well masticated, they are apt to cause distress during digestion. To insure thorough mastication, it is well to chop them fine and mix them with some other food (see Goldenrod Eggs). Hard-cooked eggs used in this way cause no digestive disturbances to the normal person.

QUESTIONS

Is it possible to cook eggs hard in water that is below the boiling point?
Explain your answer.

Why should eggs be called hard- or soft-cooked rather than hard- or soft-boiled?