Eggs are a specially interesting food because they contain all the elements necessary to the development of the young chick within the shell. The structure of the egg is familiar, with its division into the yolk and white, and it is interesting to note the details of this structure.

Break a fresh egg carefully into a saucer. The shell is porous, allowing water to evaporate from the egg and air to enter. To this porosity is due the fact that other substances may enter the egg, giving it an unnatural flavor and even hastening its deterioration. Within the shell is a fine membrane which protects the white. The yolk is also divided from the white by a more delicate membrane which enables one to separate the yolk from the white of a fresh egg. A careful examination reveals at each end of the yolk a continuation of this membrane in the form of small cords which are fastened at each end of the shell, holding the yolk evenly suspended in the center of the shell. Rough handling or jolting breaks this membrane, and the yolk drops to one side.

Lift the white carefully with a fork, and notice its elasticity. This cohesive property makes it possible to beat air into the white until the whole mass become porous. The yolk is creamy rather than light when beaten, and a bit of the yolk mixed with the white prevents the latter from becoming light and dry.

Composition of the egg.—Figure 40 gives the composition of the yolk and white taken together, and of the yolk and white separated. The protein content is high, and the fat content as well, the yolk containing a higher percentage of these two foodstuffs than the white. The mineral matter is of high value, iron and phosphorus being found in ideal forms in the yolk. In using the egg as food we are availing ourselves of one of nature’s richest storehouses. A single egg of average size yields about 75 calories, of which 60 come from the yolk and 15 from the white. A very large egg, weighing two and two thirds ounces, will yield 100 calories.

Fresh eggs and cold storage eggs.—The fresh-laid egg is always desired for its delicious flavor, and this flavor changes but little in a week or two if the egg is kept cool. It is desirable to preserve eggs, however, for future use at the season when they are most abundant and cheap. Many methods have been tried, such as laying them away in sawdust, sinking them in water-glass solution, or coating the shell with paraffin or some other substance to prevent evaporation and the entrance of air. The introduction of cold storage on a large scale promises a solution of the problem. If eggs are fresh when placed in storage, it is possible to keep them just above the freezing temperature for months without appreciable deterioration.

Eggs too long in storage may be detected by the musty odor and flavor, the running of the yolk into the white, and the thin quality of the white which prevents beating stiff. Some states have already passed stringent laws in regard to the sale of cold storage eggs.

The cost of eggs and how to buy.—The demand for fresh eggs is great, and so many eggs are exported, that the price is high, even in the summer. Twenty-five cents a dozen is a reasonable price, but this is below the average at the present date. The thirty-five or forty-cent daily allowance for food will permit the moderate use of eggs at thirty-five cents a dozen, but not a liberal use in cakes and desserts. They should be used at such a price and with that allowance as the main dish for breakfast or luncheon at times, and not in sweet dishes calling for three or four eggs. If a recipe for soft custard calls for three eggs to a pint of milk, leave out one egg or even two, and use one or two tablespoonfuls of cornstarch instead. Select eggs with a hard shell, and yolk of rich yellow. If the shell is soft and the yolk pale, these deficiencies should be reported, as they can be corrected by the poultryman. The difference in color of the shells, whether white or brown, is not of great consequence. If you can buy eggs by the crate direct from the poultryman, this is a saving, provided the eggs can be used before they deteriorate. A small crate holds fifteen dozen; the usual size thirty dozen. Some express companies have a special rate for eggs, and parcel post should aid in this method of buying.

Relative digestibility of soft and hard-cooked eggs.—The fact must be recalled that to digest is to dissolve, and that the digestion of food means a dissolving by the digestive juices, aided by water. When we speak of the digestibility of food we may mean the ease and comfort of digestion, or the length of time taken by the process, or the completeness of the process. If we take the third of these meanings, hard-cooked egg is as digestible as the soft-cooked or the raw egg, because it is completely dissolved in digestion in the course of time. If the second meaning of digestion is taken, the hard-cooked egg may be slightly less digestible, for a slightly longer time is consumed in the process. The latest researches, however, show that the digestive process is longer with any food than was formerly supposed, and the difference in this case is not especially important. Indeed, we must accept the conclusions of the scientist and frankly admit that the differences of temperature in cooking of egg do not have any great effect upon its digestibility.

Why then the popular idea that a hard-boiled egg is “absolutely indigestible”? A hard-boiled egg, or more than one, eaten rapidly, without mastication, at a picnic, and with much sweet food at an unusual hour, may interfere with the “ease and comfort in digestion” resulting from such a meal. But if the whites of the hard-boiled eggs are chopped fine, the yolk mashed, and the two served upon toast, thus insuring mastication, a dish is produced that is of average digestibility and that may be used for breakfast or luncheon without hesitation.

If a tender, jellylike consistency is wanted, cook the egg below the boiling point of water. If, however, a firmer egg is preferred, use the old-time method, and cook the egg three or four minutes in boiling water. It is the easier and quicker method.

Moreover, do not hesitate to use an egg “boiled” half an hour, provided it is chopped fine or sliced.

GENERAL METHODS AND RECIPES

Milk is the natural food of the young mammal, and contains all the foodstuffs in a form easily assimilable. Starch is not present, the carbohydrate being found in the form of lactose, or milk sugar, a sugar differing somewhat from the sugars found in vegetables and fruit (see Chapter X).

Whole milk and the milk products, cream, butter, and cheese, are all important food materials among the nations of the western world; and the manufacture of milk products, such as condensed milk, butter, and cheese, has developed large industries. While the Chinese and Japanese are two great peoples who have not utilized milk or any of its products as food for grown people to any extent, yet we are fully justified in counting these foods among the necessities. Nothing can fully take the place of milk in the family dietary.

Figure 41 shows how all the foodstuffs are represented in milk. When milk first comes from the cow the fat is suspended in tiny, invisible particles throughout the water, giving the milk its yellow tint, and the fat rises to the top in the form of cream after a few hours. The protein, sugar, and ash are dissolved in the water. When milk reaches the stomach, the protein separates from the water in the form of curd. This change is brought about by an enzyme (soluble ferment) called rennin, which is present, along with pepsin, in the gastric juice. Curd is also formed by the souring of milk through the action of bacteria, or by adding acid directly to the milk. Milk should never be gulped down, but taken in sips, so that only small portions of curd are formed in the stomach, because these are much easier to digest than large ones. Sometimes milk is soured purposely, as in buttermilk or zoolak or matzoon, that curds may form and be beaten fine before it is drunk. This is very easy to digest, because then no large curds can form. For the same reason, it is often better to take milk with bread or some other food, or to cook it in some dish. Skim milk is a valuable food, for it has everything found in whole milk but the fat. We miss the flavor of the fat in drinking it, hence it is better to use it in pudding or soup or in cooking cereals where we do not care so much about the milk flavor. Study Fig. 41, comparing the percentages of the foodstuffs in whole, skim, and buttermilk, and cream. Notice that the skim milk is higher than the whole milk in protein and sugar, that it has as much ash, and a trace of fat even. It does not tell us, however, that the forms of ash in milk are most valuable, and that it is richer in calcium than any other food material. How these foods compare in fuel value is shown in Fig. 42.

Wholesome and clean milk.—At present, the milk supply is one of our most pressing community problems, showing how closely the country and the city are united. A case of typhoid fever in one farm family, not properly cared for, may be the seed of a serious epidemic in some town. To insure clean milk to the consumer, and a fair return in money to the producer, is a great sanitary and commercial problem, not to be solved in a day.

Milk is a medium in which bacteria flourish, both the harmless and the disease producing. Typhoid fever and other fatal diseases may be carried by milk from unclean barns and dairies, and tuberculosis is possible from diseased cows. The cows must be in good health, and the stable clean. Figure 43 shows a stable with cement floor and good drainage. The cows must themselves be clean, and should be curried and washed. The milkers should have clean clothes and hands, and all receptacles should be sterilized. The milk must be rapidly cooled (see Fig. 44), bottled in sterilized bottles, kept cool during transportation, and delivered as promptly as possible to the consumer. “Certified” milk is produced and handled under the best conditions, but costs at least 15 cents a quart. Since a quart of milk is equivalent to a pound of steak or to 8 eggs, milk even at 15 to 20 cents a quart is more economical than meat and eggs at ordinary prices. At the usual price of 8 to 10 cents a quart, milk is very economical as compared with other perishable foods.

The question of preservation and pasteurization can be treated here but briefly. Preservatives are forbidden by law in most states. Pasteurization is heating at a temperature sufficiently high to kill any disease germs present, but not high enough to give a cooked taste. This process, while it destroys most of the bacteria, does not kill the spores of all. The chief arguments against pasteurization are (1) that on a commercial scale it is difficult to really accomplish this, and (2) that it is easily used to cover the sale of unclean milk. The argument for it is, that it is impossible to obtain as yet an ideal supply for a large city in hot weather, and that pasteurization, if properly conducted, kills nearly all of the dangerous bacteria and saves the lives of many babies. Clean milk that needs no pasteurization is our ultimate aim, and we must remember that milk pasteurized under unknown conditions needs to be kept cold and treated with even more care than fresh milk, for it “spoils” quite as easily, only we may not know it because it may not taste sour.

In the last few years the question of pasteurization has been studied with very great care. It is found best to heat the milk for 20 to 30 minutes at a temperature of 140° to 155° F. If it is certain that this method has been used, one need not hesitate to trust the milk, for the arguments against pasteurization do not properly apply here.

How to buy.—Investigate by question and inspection, if possible, the available milk supply. Be sure to do this in the country in the summer. Always buy bottled milk. Where the income is small, good quality milk should be used for the little children and invalids, and skim milk purchased for cooking. In many places skim milk is supplied in bottles by reliable firms. The usual price for bottled milk in the city is 8 to 10 cents, and this is of good average quality. Keep milk cold. If there is no ice, use an ice substitute (page 74), and in very hot weather pasteurize or scald the milk, cooling afterward as quickly as possible by placing in cold water and stirring the water.

GENERAL METHODS AND RECIPES

Principles of cookery.—Clean, sweet milk is an ideal food, which requires no cooking. Heating milk to 212° F. changes its properties in some way, so that it is not considered an ideal food for babies’ regular diet. If it must be used, for reasons of safety, some uncooked food, such as orange juice, should also be given. This is the reason for pasteurizing milk instead of boiling it.

Heating milk in an open vessel causes some of the protein to harden into a thin “skin” on the top. This can be prevented by stirring the milk until it is cool.