Fats are similar to carbohydrates in their general composition since they are made up of carbon, hydrogen, and oxygen, but these latter are not in the proportion to form water. There is a relatively small amount of oxygen in fat which causes a large amount of heat to be evolved in combustion. For this reason, fats are the chief source of heat and energy in the body. They also serve as a covering and protection for the body. They act as lubricants and spare the tissues from disintegration. They may also serve as a means of storing surplus energy. A person whose body is well protected by a good coating of fat is far less liable to be irritated by external nerve stimuli, such as the slamming of doors or the shouts of children, than one whose nerve ends are not so well padded.

All fats have a tendency to slow down the whole process of digestion while those having a lower melting point are more completely digested than those remaining solid at higher temperatures. Any discomfort due to the use of fat is caused by improper use or wrong cooking. When too large a quantity is taken at a time, it prevents the action of the digestive secretions on other foods, particularly those containing protein material. For this reason rich pastry and foods fried in fat should never be given to children nor invalids. If fats are overheated, they are partially split up, and produce substances which are irritating to the mucous membrane lining the intestinal tract. It is the same effect that is produced by the blue smoke which sometimes comes from the frying-pan when the fat is allowed to get too hot, and which causes the eyes and nose to water.

Digestion

The quantity of fat used in this country is far higher than the European consumption and much higher than the individual requires. It has been computed that the waste of fat in America is excessive. We should use only enough to make the food palatable and not allow any to go into the garbage pail nor down into the kitchen drain. Mr. Hoover, in his speech on November II, 1918, in Washington, before the workers of the Food Administration, said that there was a great shortage in the supplies needed by the whole world, particularly in dairy products, pork products, and vegetable oils. He said that the world would be deficient in fats for two or three years at least and that intense economy in the use of fats in this country was absolutely necessary. Nine months after the signing of the armistice, the people of England were still on their extremely low ration of fats with small prospect of immediate relief. This was a half-pound of butter and a pound of oleomargarine per person per month, whereas we use in this country an average of a quarter of a pound per person per day not including waste.

All fats are very similar chemically since they are combinations of glycerine and fatty acids. Each fat is made up of two or more of such combinations formed from fatty acids. These are steps in a long chemical series. Those which contain certain steps of the series are solid at ordinary temperature, while those that contain others in the series are oils. Difference in flavor or color is due to impurities, since a pure fat is pale yellow or colorless when liquid, and white when solid. Because they vary so little in their composition, the ones to be used in the household are those which keep the best under ordinary conditions and are best suited to the purposes for which they are intended.

Need to save fats

Nature of fats

Fat occurs in the diet in two distinct ways. It may either be a component part of the food itself as in milk, meat, and certain types of fish. Or it may be added to other foods in cooking and serving as butter, salad oils, and lard. Both of these groups should be considered by the housekeeper. The first group is regulated by a choice of the foods themselves. Care should be taken to combine a food that is in itself rich in fat, as cheese or shad, with foods that do not contain much fat; or else other fats should not be served at the same meal. One would not think of serving tartare sauce with mackerel or shad though this is almost a necessity with smelts or filet of flounder. Nor would one desire a rich dessert like a suet pudding or heavy ice-cream after roast pork, or even a salad with mayonnaise dressing. Too often are we served meals in which there is a dash of whipped cream on the soup, a tartare sauce with the fish, a rich gravy with the meat, mayonnaise with the salad, and ice-cream or whipped cream for dessert.

When we come to the second group of fats, those which are added to the foods in cooking or serving, we find there is a large region of choice and plenty of room for economy. These fats can be considered in two groups; those that are served at the table, such as butter and salad oils, and those that are used in the kitchen either as a medium for cooking as in frying or sauteing, or are added to foods as shortening. In order to save fats at the table, as small a quantity as possible should be served at a time. Butter is too costly to be used for cooking in the ordinary household, and yet any pieces that are left on the bread and butter plates at the table cannot be used in any other way. The question of salad oil depends upon the tastes of the family. There are those who feel that they would prefer to have olive oil for their salads even though it means going without some other food. Cottonseed oil and corn oil such as are found on the market to-day both make very satisfactory salad dressings and are much less expensive than the olive oil.

Use of fats

There are innumerable fats which can be used in cooking, although every housekeeper has her own favorite. Some of these are of animal origin and some of vegetable. Aside from the dairy fats, butter and cream, which are nowadays used almost exclusively at the table and not for cooking, lard is perhaps the most popular of the animal fats. Leaf lard is rendered from the fat around the kidneys of hogs. It has a moderately low melting point and therefore is easily handled as a shortening. It should be white in color and free from taste or smell. Beef fat or suet is harder than butter or lard and is somewhat highly flavored. The flavor can be improved by rendering and the fat itself made softer by mixing it with oil or lard. Mutton fat is another hard fat and because of its strong flavor is used more for soap-making than as a household fat. The fat of poultry, either fowl or goose, resembles butter and lard in its consistency and can be well used as shortening in such breadstuff's as gingerbread and pie crust where the color will not be noticeable.