Essentials of Cooking-Selection of Food

1.Each one of the phases of COOKING has its importance, but if successis to be achieved in this art, careful attention must be given to the selection of what is to be cooked, so as to determine its value and suitability. To insure the best selection, therefore, the housewife should decide whether the food material she purchases will fit the needs of the persons who are to eat it; whether the amount of labor involved in the preparation will be too great in proportion to the results obtained; whether the loss in preparation, that is, the proportion of refuse to edible matter, will be sufficient to affect the cost materially; what the approximate loss in cooking will be; whether the food will serve to the best advantage after it is cooked; and, finally, whether or not all who are to eat it will like it. The market price also is a factor that cannot be disregarded, for, as has been explained, it is important to keep within the limits of the amount that may be spent and at the same time provide the right kind of nourishment for each member of the family.
2.In order to select food material that will meet the requirementsjust set forth, three important matters must be considered; namely, the substances of which it is composed; its measure of energy-producing material, or what is called its food, or fuel, value; and its digestion and absorption. Until these are understood, the actual cost of any article of food cannot be properly determined, although its price at all times may be known. However, before a study of any of these matters is entered into, it is necessary to know just what is meant by food and what food does for the body. As is well understood, the body requires material by which it may be built and its tissues repaired when they are torn down by work and exercise. In addition it requires a supply of heat to maintain it at normal temperature and provide it with sufficient energy to do the work required of it. The material that will accomplish these important things is food, which may therefore be regarded as anything that, when taken into the body, will build and repair its tissues or will furnish it with the energy required to do its work.

Food Substances
3.Although, as has just been stated, food may be considered asanything that the human engine can make over into tissue or use in living and working, not all foods are equally desirable any more than all materials are equally good in the construction of a steam engine and in the production of its working power. Those food substances which are the most wholesome and healthful are the ones to be chosen, but proper choice cannot be made unless the buyer knows of what the particular food consists and what it is expected to do. To aid in the selection of food, therefore, it is extremely necessary to become familiar with the five substances, constituents, or principles of which foods are made up; namely, water, mineral matter, or ash, protein, fat, and carbohydrate. A knowledge of these will help also in determining the cooking methods to adopt, for this depends on the effect that heat has on the various substances present in a food. Of course, so far as flavor is concerned, it is possible for the experienced cook to prepare many dishes successfully without knowing the effect of heat on the different food constituents; but to cook intelligently, with that success which makes for actual economy and digestibility, certain facts must be known concerning the food principles and the effect of dry and moist heat on foods.
4.Water.--Of the various constituents that are found in the humanbody, water occurs in the largest quantity. As a food substance, it is an extremely important feature of a person's diet. Its chief purpose is to replenish the liquids of the body and to assist in the digestion of food. Although nature provides considerable amounts of water in most foods, large quantities must be taken in the diet as a beverage. In fact, it is the need of the body for water that has led to the development of numerous beverages. Besides being necessary in building up the body and keeping it in a healthy condition, water has a special function to perform in cooking, as is explained later. Although this food substance is extremely essential to life, it is seldom considered in the selection of food, because, as has just been mentioned, nearly all foods contain water.
5.Mineral Matter.--Ranking next to water in the quantity contained in the human body is mineral matter. This constituent, which is also called ash or mineral salts, forms the main part of the body's framework, or skeleton. In the building and maintaining of the body, mineral salts serve three purposes--to give rigidity and permanence to the skeleton, to form an essential element of active tissue, and to provide the required alkalinity or acidity for the digestive juices and other secretions. The origin and distribution of these mineral substances are of interest. Plants in their growth seize from the earth the salts of minerals and combine them with other substances that make up their living tissue. Then human beings, as well as other living creatures, get their supply of these needed salts from the plants that they take as food, this being the only form in which the salts can be thoroughly assimilated. These salts are not affected by cooking unless some process is used that removes such of them as are readily soluble in water. When this occurs, the result is usually waste, as, for instance, where no use is made of the water in which some vegetables are boiled. As is true of water, mineral matter, even though it is found in large quantities in the body, is usually disregarded when food is purchased. This is due to the fact that this important nutritive material appears in some form in nearly all foods and therefore does not necessitate the housewife's stopping to question its presence.
6.Protein.--The food substance known as protein is a very importantfactor in the growth and repair of the body; in fact, these processes cannot be carried on unless protein is present in the diet. However, while a certain quantity of protein is essential, the amount is not very large and more than is required is likely to be harmful, or, since the body can make no use of it, to be at least waste material. The principal sources of protein are lean meat, eggs, milk, certain grains, nuts, and the legumes, which include such foods as beans and peas. Because of the ease with which they are digested, meat, fish, eggs, and milk are more valuable sources of protein than bread, beans, and nuts. However, as the foods that are most valuable for proteins cost more than others, a mixed diet is necessary if only a limited amount of money with which to purchase foods is available.
7.So much is involved in the cooking of foods containing protein thatthe effect of heat on such foods should be thoroughly understood. The cooking of any food, as is generally understood, tends to break up the food and prepare it for digestion. However, foods have certain characteristics, such as their structure and texture, that influence their digestibility, and the method of cooking used or the degree to which the cooking is carried so affects these characteristics as to increase or decrease the digestibility of the food. In the case of foods containing protein, unless the cooking is properly done, the application of heat is liable to make the protein indigestible, for the heat first coagulates this substance--that is, causes it to become thick--and then, as the heat increases, shrinks and hardens it. This fact is clearly demonstrated in the cooking of an egg, the white of which is the type of protein called albumin. In a raw egg, the albumin is nearly liquid, but as heat is applied, it gradually coagulates until it becomes solid. If the egg is cooked too fast or too long, it toughens and shrinks and becomes less palatable, less attractive, and less digestible. However, if the egg is properly cooked after the heat has coagulated the albumin, the white will remain tender and the yolk will be fine and mealy in texture, thus rendering it digestible. Similar results, although not so evident to the sight, are brought about through the right or wrong way of cooking practically all other foods that contain much protein. Milk, whose principal ingredient is a protein known as casein, familiar as the curd of cheese, illustrates this fact very plainly. When it is used to make cottage cheese, heating it too long or to too high a degree will toughen the curd and actually spoil the texture of the product, which will be grainy and hard, instead of smooth and tender.
8.FATS.--The food substances just discussed--water, mineral matter,and protein- yield the materials required for building and repairing the tissues of the body, but, as has been explained, the body also requires foods that produce energy, or working power. By far the greater part of the total solids of food taken into the body serve this purpose, and of these fats form a large percentage. Although fats make up such a large proportion of the daily food supply, they enter into the body composition to a less extent than do the food substances that have been explained. The fats commonly used for food are of both animal and vegetable origin, such as lard, suet, butter, cream, olive oil, nut oil, and cottonseed oil. The ordinary cooking temperatures have comparatively little effect on fat, except to melt it if it is solid. The higher temperatures decompose at least some of it, and thus liberate substances that may be irritating to the digestive tract.
9.CARBOHYDRATES.--Like fats, the food substances included in the termcarbohydrates supply the body with energy. However, fats and carbohydrates differ in the forms in which they supply energy, the former producing it in the most concentrated form and the latter in the most economical form. So that the term carbohydrate may be clearly understood and firmly fixed in the mind, it is deemed advisable to discuss briefly the composition of the body and the food that enters it. Of course, in a lesson on COOKING, not so much attention need be given to this matter as in a lesson on dietetics, which is a branch of hygiene that treats of diet; nevertheless, it is important that every person who prepares food for the table be familiar with the fact that the body, as well as food, is made up of a certain number of chemical elements, of which nitrogen, carbon, hydrogen, and oxygen form a large part. Protein owes its importance to the fact that of the various food substances it alone contains the element nitrogen, which is absolutely essential to the formation of any plant or animal tissue. The other three elements, carbon, hydrogen, and oxygen, go to make up the carbohydrates; in fact, it is from the names of these three elements that the term carbohydrate is derived. The carbohydrates include the starches and sugars that are used and eaten in so many forms, and these contain the three elements mentioned, the hydrogen and oxygen contained in them being in the proportion that produces water. Thus, as will readily be seen, by separating the name into its parts--carbo (carbon) and hydrate (hydrogen and oxygen in the proportion of two parts of hydrogen and one of oxygen, that is, in the form of water)--carbohydrate is simply carbon united with water. While the facts just brought out have much to do with food economy, they are of interest here chiefly because they help to make clear the term carbohydrate, which, as will be admitted, is the only correct name for the food substance it represents.
10.STARCH, one of the chief forms of carbohydrates, is found in onlythe vegetable kingdom. It is present in large quantities in the grains and in potatoes; in fact, nearly all vegetables contain large or small amounts of it. It is stored in the plant in the form of granules that lie within the plant cells. Cooking applied to starch changes it into a form that is digestible. Moist heat cooks the granules until they expand and burst and thus thicken the mass. Dry heat changes starch first into a soluble form and finally into what is called dextrine, this being the intermediate step in the changing of starch into sugar.
11.SUGAR, another important form of carbohydrate, is mainly ofvegetable origin, except that which is found in milk and called lactose. This, together with the fat found in milk, supplies the child with energy before it is able to digest a variety of foods. The sap of various plants contains such large quantities of sugar that it can be crystallized out and secured in dry form. The liquid that remains is valuable as food, for, by boiling it down, it forms molasses. Sugar is also present in considerable amounts in all fruits, and much of it is in a form that can be assimilated, or taken up by the body, quickly. A sugar very similar to this natural fruit sugar is made from the starch of corn and is called glucose. Much of the carbohydrate found in vegetables, especially young, tender vegetables, is in the form of sugar, which, as the vegetables grow older, changes to starch. Sugar melts upon the application of heat or, if it is in a melted condition, as syrup or molasses, it boils down and gives off water. When all the water has boiled away, the sugar begins to caramelize or become brown, and develops a characteristic flavor. If the cooking is continued too long, a dark-brown color and a bitter taste are developed. Because the sugar in fruits and vegetables is in solution, some of it is lost when they are boiled, unless, of course, the water in which they are cooked is utilized.
12.CELLULOSE is a form of carbohydrate closely related to starch. Ithelps to form the structure of plants and vegetables. Very little cellulose is digested, but it should not be ignored, because it gives the necessary bulk to the food in which it occurs and because strict attention must be paid to the cooking of it. As cellulose usually surrounds nutritive material of vegetable origin, it must be softened and loosened sufficiently by cooking to permit the nutritive material to be dissolved by the digestive juices. Then, too, in old vegetables, there is more starch and the cellulose is harder and tougher, just as an old tree is much harder than a sapling. This, then, accounts for the fact that rapid cooking is needed for some vegetables and slow cooking for others, the method and the time of cooking depending on the presence and the consistency of the cellulose that occurs in the food.
13.Every one of the five foodsubstances just considered must be included in a person's diet; yet, with the exception of milk, no single food yields the right amounts of material necessary for tissue building and repair and for heat and energy. Even milk is in the right proportion, as far as its food substances are concerned, only for babies and very young children. It will thus be seen that to provide the body with the right foods, the diet must be such as to include all the food substances. In food selection, therefore, the characteristics of the various food substances must be considered well. Fats yield the most heat, but are the most slowly digested. Proteins and carbohydrates are more quickly digested than fats, but, in equal amounts, have less than half as much food value. Water and mineral salts do not yield heat, but are required to build tissue and to keep the body in a healthy condition. In addition, it is well to note that a well-balanced diet is one that contains all of the five food substances in just the right proportion in which the individual needs them to build up the body, repair it, and supply it with energy. What this proportion should be, however, cannot be stated offhand, because the quantity and kind of food substances necessarily vary with the size, age, and activity of each person.

Food Value
14.Nearly all foods are complex substances, and they differ from oneanother in what is known as their value, which is measured by the work the food does in the body either as a tissue builder or as a producer of energy. However, in considering food value, the person who prepares food must not lose sight of the fact that the individual appetite must be appealed to by a sufficient variety of appetizing foods. There would be neither economy nor advantage in serving food that does not please those who are to eat it. While all foods supply the body with energy, they differ very much in the quantity they yield. If certain ones were chosen solely for that purpose, it would be necessary for any ordinary person to consume a larger quantity of them than could be eaten at any one time. For instance, green vegetables furnish the body with a certain amount of energy, but they cannot be eaten to the exclusion of other things, because no person could eat in a day a sufficient amount of them to give the body all the energy it would need for that day's work. On the other hand, certain foods produce principally building material, and if they were taken for the purpose of yielding only energy, they would be much too expensive. Meats, for example, build up the body, but a person's diet would cost too much if meat alone were depended on to provide the body with all the energy it requires. Many foods, too, contain mineral salts, which, as has been pointed out, are needed for building tissue and keeping the body in a healthy condition.
15.To come to a correct appreciation of the value of different foods,it is necessary to understand the unit employed to measure the amount of work that foods do in the body. This unit is the CALORIE, and it is used to measure foods just as the inch, the yard, the pound, the pint, and the quart are the units used to measure materials and liquids; however, instead of measuring the food itself, it determines its food value, or fuel value. To illustrate what is meant, consider, for instance, 1/2 ounce of sugar and 1/2 ounce of butter. As far as the actual weight of these two foods is concerned, they are equal; but with regard to the work they do in the body they differ considerably. Their relative value in the body, however, can be determined if they are measured by some unit that can be applied to both. It is definitely known that both of them produce heat when they are oxidized, that is, when they are combined with oxygen; thus, the logical way of measuring them is to determine the quantity of heat that will be produced when they are eaten and united with oxygen, a process that causes the liberation of heat. The calorie is the unit by which this heat can be measured, it being the quantity of heat required to raise the temperature of 1 pint of water 4 degrees Fahrenheit, which is the name of the thermometer commonly used in the home. When burned as fuel, a square of butter weighing 1/2 ounce produces enough heat to raise 1 pint of water 400 degrees Fahrenheit, and it will yield the same amount of heat when it is eaten and goes through the slow process of oxidation in the body. On the other hand, 1/2 ounce of sugar upon being oxidized will produce only enough heat to raise the temperature of 1 pint of water about 230 degrees Fahrenheit. Thus, as will be seen, 1/2 ounce of butter has a value of approximately 100 calories, whereas 1/2 ounce of sugar contains only about 57-1/2 calories. Other foods yield heat in varying degrees, and their food value is determined in exactly the same way as that of butter and sugar. To give an idea of the composition of various food materials, as well as the number of calories that 1 pound of these food materials will yield, food charts published by the United States Department of Agriculture are here presented. As an understanding of these charts will prove extremely profitable in the selection of food, a careful study of them at this time is urged. In addition, reference to them should be made from time to time as the various kinds of foods are taken up, as the charts will then be more easily comprehended and their contents of more value.

16. The third requirement in the selection of food, namely, itsdigestion and absorption, depends considerably on the persons who are to be fed. Food that is chosen for adults entirely would not be the same as that intended for both young persons and adults; neither would food that is to be fed to children or persons who are ill be the same as that which is to be served to robust adults who do a normal amount of work. No hard-and-fast rules can be laid down here for this phase of food selection, but as these lessons in COOKING are taken up in turn, the necessary knowledge regarding digestibility will be acquired.

17. The term COOKING, as has been explained, means the preparation ofboth hot and cold dishes for use as food, as well as the selection of the materials or substances that are to be cooked. The importance of cooking foods by subjecting them to the action of heat has been recognized for ages; and while it is true that there are many foods that appeal to the appetite in their raw state and still others that can be eaten either raw or cooked, there are several reasons why it is desirable to cook food, as will be seen from the following:
1.Cooking makes foods more palatable. This is true of such foods asmeat, cereals, and many vegetables, which would be very unappetizing if they were eaten raw.
2.Cooking renders foods more digestible. For instance, the hard grains,such as wheat, and the dried vegetables, such as beans, cannot be readily digested unless they are softened by cooking. But while cooking makes such foods more digestible, it renders others more difficult of digestion, as in the case of eggs, the degree of digestibility depending somewhat on the cooking method used and the skill of the cook. An egg in an almost liquid form, or when only slightly cooked, as a soft-boiled egg, is more easily digested than when it becomes hardened by cooking. Then, too, a properly prepared hard-cooked egg is more digestible than an improperly cooked one, although the degree of hardness may be the same.
3.Cooking gives foods greater variety. The same food may be cooked byvarious methods and be given very different tastes and appearances; on the other hand, it may be combined with a large number of other foods, so as to increase the variety of the dishes in which it is used. The large number of recipes found in cook books show the attempts that have been made to obtain variety in cooked dishes by the combining of different foods.
4.Cooking sterilizes foods either partly or completely. Many foodsneed partial or complete sterilization for safety. They must be completely sterilized if the germs that produce fermentation or putrefaction and thereby spoil food would be destroyed. This is done when fruits and vegetables are canned for keeping. Foods that are exposed to dust, flies, and improper handling should be thoroughly cooked in order to destroy any pathogenic germs that might be present. By such germs are meant disease-bearing germs. They differ from germs that produce fermentation and putrefaction, or spoiling, and that must in general be considered as a help, for these play an important part in the raising of bread and the preparation of various foods, as is pointed out later.
5.Cooking develops flavor in many foods. In the case of somevegetables, the flavoring substance is given off in the air by certain methods of cooking and a better flavor is thereby developed.

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