It has been stated that "a quart of milk, three-quarters of a pound of moderately lean beef, and five ounces of wheat flour contain about the same amount of nutritive material;" but we pay different prices for them, and they have different values for nutriment. The milk comes nearest to being a perfect food. It contains all the different kinds of nutritive materials that the body requires. Bread made from wheat flour will support life. It contains all the necessary ingredients for nourishment, but not in the proportion best adapted for ordinary use. A man might live on beef alone, but it would be a very one-sided and imperfect diet. Meat and bread together make the essentials of a healthful diet. In order to give a general idea of food economy, it will be necessary to deal briefly with the functions of the various food principles. As our bodies contain a great deal of muscle, the waste of which is repaired by protein found in such food as lean meat, eggs, cheese, beans, peas, oatmeal, fish, etc., a supply of these articles must be considered in purchasing the daily supply. Fatty tissue (not muscle) serves as fuel, therefore the value of such foods as butter, cream, oils, etc., is apparent. Carbohydrates form fat and serve as fuel and force producers; these come in the form of starches, sugars,—vegetables and grains being the most important. In being themselves burned to yield energy, the nutrients protect each other from being consumed. The protein and fats of body tissue are used like those of foods. An important use of the carbohydrates and fats is to protect protein (muscle, etc.) from consumption. "The most healthful food is that which is best fitted to the wants of the user: the cheapest food is that which furnishes the largest amount of nutriment at the least cost: the best food is that which is both healthful and cheap." By referring to the various charts a fair estimate of food values may be obtained.

As will be noticed, the animal foods contain the most protein and fats, while the vegetable foods are rich in carbohydrates. A pound of cheese may have 0.28 pound of protein, as much as a man at ordinary work needs for a day's sustenance, while a pound of milk would have only 0.04, and a pound of potatoes 0.02 pound of protein. The materials which have the most fats and carbohydrates have the highest fuel value. The fuel value of a pound of fat pork may reach 2.995 calories, while that of a pound of salt codfish would be only .315 calories. On the other hand, the nutritive material of the codfish would consist almost entirely of protein, while the pork contains very little. Among the vegetable foods, peas and beans have a high proportion of protein. Oatmeal contains a large proportion also. Potatoes are low in fuel value as well as in protein, because they are three-fourths water. For the same reason milk, which is seven-eights water, ranks low in respect to both protein and fuel value, hence the reason why it is not so valuable as food for an adult as many of the other food materials.

These few illustrations will help to show the need of an intelligent idea of food values before attempting to purchase the supplies for family use. As one-half a laboring man's income goes towards providing food, it must follow that such knowledge will help the housewife very materially in securing the best results from the amount expended.

The average daily diet of an adult should contain (Church):—

Quantity of Food Required.

The quantity of food required to maintain the body in a vigorous condition depends upon the following conditions:—(1) Climate and season, (2) clothing, (3) occupation, (4) age and sex. In civilized countries more food is eaten, as a rule, than is necessary to maintain health and strength. Climate and seasons influence the quantity of food eaten. A cold, bracing atmosphere stimulates the appetite, tempts one to exercise, while a hot climate has the contrary effect; hence the need for more or less food. Abundant clothing in cold weather conserves the body heat; less food is therefore required to maintain life. Exercise and muscular work cause greater oxidation in the tissues and greater waste of the muscles; this must be replaced by proper food. Outdoor work requires more food than indoor, and physical labor more than mental. It has been estimated "that a child of ten years requires half as much food as a grown woman, and one of fourteen an equal amount. The rapidly growing active boy often eats as much as a man, and the middle-aged man requires more than the aged. A man of seventy years may preserve health on a quantity which would soon starve his grandson."

Just what ingredients of the food serve for nourishment of the brain and nerves, and how they do that service, are mysteries which have not yet been solved. Brain and nerve contain the elements nitrogen and phosphorus, which are found in protein compounds but not in the true fats, sugars, and starches, which contain only carbon, hydrogen and oxygen. We naturally infer that the protein compounds must be especially concerned in building up brain and nerve, and keeping them in repair. Just how much food the brain worker needs is a question which has not yet been decided. In general it appears that a man or a woman whose occupation is what we call sedentary, who is without vigorous exercise and does but little hard muscular work, needs much less than the man at hard manual labor, and that the brain worker needs comparatively little of carbohydrates or fats. Many physicians, physiologists and students of hygiene have become convinced that well-to-do people, whose work is mental rather than physical, eat too much; that the diet of people of this class as a whole is one-sided as well as excessive, and that the principal evil is the use of too much fat, starch and sugar. It is well to remember that it is the quantity of food digested which builds the body, and more injury is likely to result from over-eating than from a restricted diet, hence the value of having food cooked so as to aid digestion. The following dietary standards may be interesting to the more advanced pupils, housewives, etc.:—

Quality of Food.

It is a great mistake to think that the best is the cheapest in regard to the food question, that the higher priced meats, fish, butter, etc., contain special virtues lacking in the cheaper articles. Poor cooking is the chief cause of this error in judgment. No doubt a well broiled steak is more appetizing and delicate in flavor than some of the cheaper cuts, but in proportion to the cost is not equal in nutritive value; careful cooking and judicious flavoring render the cheaper pieces of beef equally palatable. That expensive food is not necessary to maintain life has been clearly demonstrated by the traditional diet of the Scotch people with their oatmeal and herring; the Irish, potatoes and buttermilk; New England, codfish and potatoes, and pork and beans; the Chinese, rice, etc. Monotony of diet, however, is not recommended, for reasons given in a previous chapter, and in the countries where a special diet prevails owing to the climate, nature of soil and markets, the results have not warranted us in believing that it is as good as a mixed diet. From this necessarily brief outline of the food question we have learned (1) that a knowledge of the requirements of the body are absolutely necessary in regulating a proper diet; (2) to furnish the food principles in a cheap rather than a dear form; (3) to understand the art of cookery so as to secure the full nutritive value and at the same time stimulate the appetite; (4) the value of economy in regard to food principles. When the housekeeper has acquired this knowledge she will have covered the field of food economy. Prof. Atwater says: "When we know what are the kinds and amount of nutritive substances our bodies need and our food materials contain, then and not till then shall we be able to adjust our diet to the demands of health and purse."

Cooking of Food.

It is sometimes asked, why do we cook our food? As many opportunities will occur during this course of instruction for a comparison of the customs and diet of the various countries, and the advance of civilization in this direction, we will confine ourselves to the definition of the term as it concerns ourselves.

Mr. Atkinson says, that "Cooking is the right application of heat for the conversion of food material."

As much of our food requires cooking, how we shall cook it so as to render it more palatable, more digestible, and with the greatest economy of time, fuel and money, is an object deserving the most careful attention. The art of cooking lies in the power to develop certain flavors which are agreeable to the palate, or in other words, which "make the mouth water," without interfering with the nutritive qualities of the food prepared, to understand by what method certain foods may be rendered more digestible, and to provide variety. Monotony of diet and of flavor lessens the appetite and fails to stimulate the digestive organs.

The chemical changes, produced by cooking food properly, aid digestion, beside destroying any germs which may be contained in the food. Nearly all foods—except fruit—require cooking. The digestibility of starch depends almost entirely upon the manner in which it is cooked, especially the cereal class. Gastric troubles are sure to follow the use of improperly cooked grains or starches. (See Chap. VII.)

Methods.

The following are the usual methods observed in cooking, viz.: (1) boiling, (2) stewing, (3) roasting, (4) broiling, (5) frying, (6) braising, (7) baking, (8) steaming.

Water boils at a temperature of 212° F. Simmering should be at a temperature of from 175° F. to 180° F. When water has reached the boiling point, its temperature cannot be raised, but will be converted into steam; hence the folly of adding fuel to the fire when water has already reached the boiling point.

Stewing allows the juices of the meat to become dissolved in water heated to the simmering point. The juices thus dissolved are eaten with the meat. If not injured by the addition of rich sauces or fats, this is usually a very digestible method of preparing certain kinds of meat.

Broiling is cooking directly over the hot coals. A coating of coagulated albumen is formed upon the outer surface. This coating prevents the evaporation of the juices, which with the extractive materials are retained and improve the flavor. Meat cooked in this way has a decided advantage, in both flavor and nutritive value, over that which has been boiled or stewed. There are, however, only certain kinds of meat that are suitable for broiling.

Frying is cooking in hot fat. The boiling point of fat is far above that of water. Fat should not be heated above 400° F., as it will then turn dark and emit a disagreeable odor. Fried food, unless very carefully prepared, is considered unwholesome. The only proper method for frying is to immerse the food completely in a bath of hot fat.

Braising is cooking meat in a covered vessel surrounded by a solution of vegetable and animal juices in a strong but not boiling temperature. Tough meat may be rendered very palatable and nutritious by cooking in this way. The cover of the pan or kettle must fit closely enough to prevent evaporation. It requires long, steady cooking. The flavor is improved by browning the meat in either hot fat or in a very hot oven before braising.

Baking is cooking in confined heat. Meat properly cooked in an oven is considered by many authorities as quite equal in delicacy of flavor to that roasted before a fire, and is equally digestible.

Steaming is cooking food over condensed steam, and is an excellent method for preparing food which requires long, slow cooking. Puddings, cereals, and other glutinous mixtures are often cooked in this way. It is an economical method, and has the advantage of developing flavor without loss of substance.

Food Preservation.

Food is preserved by the following processes: (1) drying, (2) smoking, (3) salting, (4) freezing, (5) refrigerating, (6) sealing, (7) addition of antiseptic and preservative substances.

Drying in the sun and before a fire is the usual method employed by housekeepers. Fruits and vegetables, meat and fish may be preserved by drying, the latter with the addition of salt.

Smoking is chiefly applied to beef, tongue, bacon, ham, and fish, which are hung in a confined chamber, saturated with wood smoke for a long time until they absorb a certain percentage of antiseptic material, which prevents the fat from becoming rancid, and the albumen from putrefying. Well smoked bacon cut thin and properly cooked is a digestible form of fatty food, especially for tubercular patients. Smoking improves the digestibility of ham.

Salting is one of the oldest methods of preserving food. The addition of a little saltpetre helps to preserve the color of the meat. Brine is frequently used to temporarily preserve meat and other substances. Corned beef is a popular form of salt preservation. All salted meats require long, slow cooking. They should always be placed in cold water and heated gradually in order to extract the salt. Salt meats are less digestible and not quite so nutritious as fresh meats.

Food may be kept in a frozen condition almost indefinitely, but will decompose very quickly when thawed, hence the necessity for cooking immediately. Frozen meat loses 10 per cent. of its nutritive value in cooking.

This process does not involve actual freezing, but implies preservation in chambers at a temperature maintained a few degrees above freezing point. This method does not affect the flavor or nutritive value of food so much as freezing.

Sealing is accomplished not only in the process of canning but by covering with substances which are impermeable. Beef has been preserved for considerable time by immersing in hot fat in which it was allowed to remain after cooling.

Chemicals are sometimes used in the preservation of food, but the other methods are safer.