40. In the beating of eggs, it should be remembered that for some purposes, as in making some kinds of sponge cake, they are beaten until nearly frothy, as shown in Fig. 10, when they do not stand up nor cling to the whip; whereas, for other purposes, as in making meringue, they are beaten until they are stiff enough to stand up well and to adhere to the whip, as Fig. 11 shows. When egg whites are to be beaten stiff, care should be taken not to continue the beating too long. If this is done, they will become dry and will break up into small pieces, a condition that will mean a loss of some of the air that has been incorporated. It is well also to observe that egg whites should always be beaten in the same direction and that the same motion should be continued throughout the beating, for a change of direction or motion always causes a loss of air. A final precaution to take is never to allow egg whites to stand after they are beaten. If this is done, the leavening power of the eggs is reduced, because the air soon escapes from beaten eggs and leaves underneath them a clear liquid that can never be beaten up. For instance, eggs that are to be used for boiled icing should not be beaten until the sirup has finished boiling. However, eggs that have been separated but not beaten may stand for a couple of hours, provided they are covered and kept in a cool place.
POINTS TO OBSERVE IN COOKING EGGS
41. As has been previously stated, the substance in eggs that requires special care in the cooking process is the protein, which occurs in this food in the form of albumen. Because of this, certain points concerning the treatment that the albumen requires should be kept in mind. In a raw egg, the albumen occurs in a semiliquid form, but it coagulates at a lower temperature than does the yolk, which contains a high percentage of fat. After coagulation, the consistency of the two parts is very different. The white is elastic and more or less tough, while the yolk, upon being thoroughly cooked, becomes powdery, or mealy, and breaks up into minute particles. The egg white begins to coagulate at 134 degrees Fahrenheit, and it becomes white and jellylike at 160 degrees. Bringing an egg to such a temperature produces a more desirable result than cooking it at a high temperature--boiling point, for instance--because the albumen, instead of becoming tough, as it does at a high temperature, acquires a soft, tender consistency that exists throughout the entire egg. An egg cooked in this way is more digestible and appetizing than one that is boiled until it becomes hard and tough.
42. The low temperature at which eggs will cook in the shell applies also to eggs when they are combined with other foods. Sometimes, however, a mixture in which eggs are one of the ingredients must be cooked at a high temperature because the materials mixed with them require it. This difficulty can be overcome when eggs are combined with starchy foods, such as corn starch, rice, and tapioca, that require long cooking. In such a case, all the ingredients except the eggs may be cooked the length of time they require, after which the eggs may be added so that they will cook just long enough to become coagulated. Longer cooking is liable to spoil the texture. Often the starchy mixture retains sufficient heat to set the eggs without further cooking after they are added.
43. A very nutritious way in which to prepare eggs when they are to be used for a dessert is to combine them with milk to form a custard, which, after being sweetened and flavored, is baked. The proportion that has been accepted as ideal to produce a dessert of the right thickness is one egg to each cupful of milk; however, an entire egg is not always required, as one yolk is often sufficient to thicken 1 cupful of milk. Care should be taken in the cooking of such custards, for if they are cooked too long or at too high a temperature they will curdle and whey; whereas, a properly cooked custard--that is, one cooked slowly at a low temperature and for the required length of time--will have a smooth, jellylike consistency. A slight variation in a dish of this kind is secured by reducing the number of eggs and thickening it with corn starch or some other starchy material. While such a mixture is not a true custard, it makes an excellent dessert.