Eggs, next to milk, are the most valuable form of food for those who are very ill. They contain in excellent proportion most of the elements necessary to nourish the body; but being a concentrated form of food, it is well to associate with them milk or some other liquid, and such starchy foods as bread, potatoes, etc.
According to Lawes and Gilbert the composition of egg is as follows:
| Shell | Carbonate of lime | 10.00% | |
| { | Nitrogenous matter | 16.00% | |
| { | Fatty matter | 30.70% | |
| Yolk | { | Saline matter | 1.30% |
| { | Water | 52.00% | |
| ——— | |||
| Total | 100.00% | ||
| { | Nitrogenous matter | 20.40% | |
| White | { | Saline matter | 1.60% |
| { | Water | 78.00% | |
| ——— | |||
| Total | 100.00% |
A large proportion of both yolk and white is albumen.[35] It has been found by experiment ([page 25]) that when white of egg is subjected to a temperature of 134°-140° Fahr. little white threads appear in it; that if the temperature be increased to 160° Fahr., the whole mass becomes a white, but tender, easily divided substance; that if the heat be raised to 200° Fahr. it loses its tender, jelly-like consistency, and becomes firm and tenacious; and that with continued rise of temperature the toughness increases until at from 300°-350° Fahr. it becomes so hard that it is used as a cement for marble.
From these statements it will at once be inferred that the proper cooking temperature of eggs is not that of boiling water, but 52° lower. Eggs cooked the customary three minutes in boiling water will be overdone in the part nearest the shell, and not cooked at all in the center of the yolk, as three minutes is not long enough for the heat to penetrate to that point. The yolk, though not injurious in this condition, is not as palatable as when it is cooked. The condition of the white, however, is of grave importance, as even well persons are sometimes made ill by eating it.
It is generally agreed that although albumen will coagulate at a temperature somewhat lower than 160° Fahr., the degree of firmness obtained by exposing it to this temperature is the most desirable for food. Therefore we speak of 160° Fahr. as its cooking temperature. An egg cooked ideally would be subjected to that temperature for a sufficient time to allow the heat to penetrate and act upon all portions of it. The time required is half an hour. Cooked according to this method, the white would be opaque and firm, but tender and delicate, the yolk not liquid and lukewarm, but thick and almost firm. The flavor of both is delicious.
A knowledge of the proper temperature necessary to bring about this change is absolutely essential to any one who would cook eggs, and dishes which contain them, such as creams, puddings, etc., as they should be cooked. A great deal of the philosophy of cooking depends upon this knowledge, for nearly all kinds of meat, fish, oysters, milk, and other albuminous foods contain as one of their most valuable nutrients the substance known as albumen. When they are cooked with reference to this alone, we find that they are also done in the best-known way with reference to their other ingredients.
Practically with our present kitchen appliances it is exceedingly difficult to maintain for half an hour a steady temperature of 160°, but excellent results may be obtained by the following method.
SOFT-COOKED EGGS
Pour enough boiling water into a saucepan to more than cover whatever number of eggs are to be cooked; then put in the eggs, and let them stand for ten minutes on the hearth or any place where the water will not lose its warmth too quickly. Remember that it is the heat in the water which is to do the cooking. The saucepan should remain uncovered. Practically this is an excellent way to do, for the amount of heat in the water will not fall below 160° Fahr. in the ten minutes, and that time is sufficient for it to penetrate to the center of the egg. Moreover, if the egg be forgotten, and remains in the water for a longer time, it will not become hard unless the temperature of the water be raised.