What foods have we found to contain fat? What uses have we made of fat in cooking? What are the uses of fat in the body? (Pp. 72, 140, 141.)

Distinction Between Fats And Oils

We know that fats and oils are alike greasy, and that fat, by heating, may be changed to oil. Some fats are soft and oily, others firm and hard. The softer a fat is the less heat it takes to melt it. An oil is a fat that is liquid at ordinary temperatures.

Most fats contain stearin and palmitin, solid fatty sub-stances, and olein, a liquid. The more stearin fat contains the harder it is. Oils consist chiefly of olein, in which some palmitin and stearin are dissolved.

Vegetable Fats And Oils

The fat of most plants is in the form of oil. Cocoa-butter is an exception. (P. 345.) Seeds, particularly nuts and kernels of grains, are rich in oil, stored up, as starch is, to feed the seedling. Olive oil is extracted by pressure from the fruit of the olive tree. Olives are about the size of plums. Some varieties, when ripe, are purple, some green, others yellow. The best oil is obtained from the first pressing of fresh, carefully picked fruit; a poorer grade, from a second pressing; and after treating the mass of pulp with hot water, or with chemicals, a third grade, used for soap-making.

U. S. Department of Agriculture Office of Experiment Stations A. C. True: Director

Prepared by C. F. Langworthy Expert in Charge of Nutrition Investigations

Composition Of Food Materials.

Chart 7.

Chart 7.

Cottonseed oil is as nutritious as olive oil, but inferior in flavor. The cottonseeds are first chopped, hulled, rolled, and cooked. Then they are put in bags and the oil is pressed out. Oil for table use is refined. The mass of seeds left, called "oil-cake," makes good cattle food. Cottonseed oil mixed with suet and other fats forms a lard-like substance sold under various trade-names for frying and shortening.

Oils from other seeds and nuts, corn, peanuts, cocoanuts, rape, sesame, and others are used for food.

Nuts, generally speaking, are rich in fat and contain considerable protein and ash, but not much starch. They are a concentrated food and should be eaten as a part of the diet, not as an extra tid-bit. Peanut butter and other nut-pastes are desirable foods.

Animal Fats

Butter and lard are the animal fats most commonly used for food. Butter-fat seems to contain something which makes it more useful in the body than lard or vegetable oils. It is the most palatable of raw fats, and therefore can be taken into the body in large quantities. (For butter, see pp. 99-101; for lard, p. 182.)

Butterine (oleomargarine) is a substitute for butter made from a mixture of animal and vegetable fats churned with milk. A little genuine butter is usually added to flavor it. Butterine is wholesome and a better article of food than most so-called "cooking-butter," but less palatable and less desirable for steady use than good butter.

Food Value Of Fat

We have learned that fat has a fuel value more than twice as great as that of protein or carbohydrate. (See Carbohydrates, p. 72 and Food requirements, p. 146.) This is why we incline to eat more of it in cold weather than in warm, why Esquimaux and Arctic explorers enjoy whale-blubber and walrus-fat. But theoretically we could do without it. The body does not use fat exclusively for fuel, and if no fat were supplied, it would merely have to burn more carbohydrate and protein. Fat is more expensive than carbohydrate. Yet everywhere, even in hot countries, it forms part of the diet. There are two reasons for this besides its high fuel value. First, it does not require much digestion. (See What digestion is, p. 366.) Second, fat is readily stored in the body. (P. 142.) If any protein or carbohydrate has to be stored, a good deal of work must first be done on it by the body.

Cooking As It Affects The Digestibility Of Foods Containing Fat

If not properly cooked, fat may make more work for the body than it saves. Fat itself is most readily digestible when finely divided, as in milk, or in such form that it can be quickly divided, as in crisp bacon. Instinctively we prefer to spread butter on bread, and in general, to eat fat in combination with other food. But it is not well to incorporate it so closely with other food that particles of this are coated with grease, as in toast soaked with melted butter, or in fried food that has soaked up fat. In this case the fat, since it is not affected at all by saliva and but little by gastric juice, tends to act as a seal, and prevent these juices from reaching the starches and proteins in the food.

U.S. Department of Agriculture Office of Experiment Stations A.C. True: Director

Prepared by

C.F. Langworthy

Expert in Charge of Nutrition Investigations

Composition Of Food Materials.

Chart 8.

Chart 8.

These, therefore, run the risk of remaining undigested until the fat is removed from them in the intestine, and may never be thoroughly digested and absorbed. With pastry the case is still worse, for in this not only is shortening so rubbed into the flour that it may envelop starch-granules, but so little water is added that these cannot swell as they should. If pastry is to be made at all, pains should be taken to have it light and crisp. Burned fat contains indigestible and irritating substances.

Directions For Cooking Bacon

Have the bacon sliced as thin as possible. Provide a jar or small bowl for the fat which will cook out of the bacon, and a pan with several thicknesses of brown paper laid on it for draining the bacon. Heat the frying-pan, and put the bacon in. As the melted fat accumulates, pour it into the jar. Turn the bacon with a fork. Remove as fast as it is done and drain on the paper before placing on hot platter. The bacon should be crisp, but not scorched. If a great deal of smoke begins to rise from the pan during cooking, reduce the heat.