Peanuts, which are so widely used as food, are on the boundary line between nuts and legumes. They were classed as peas by some of the early botanists, and as nuts by others. The name indicates the compromise that was made between the two theories. Another legume, which is largely used in Japan and China is the soy-bean. Both the peanut and the soy-bean are better balanced, and more nutritious than common beans and peas. They are similar in composition, and contain about equal quantities of protein and fat, some peanuts yielding as much as 48 or 50 per cent oil. Neither are palatable in their natural state, but both are very delicious when their starch content is converted into dextrin by roasting. The Japanese have a method of preparing the soy-bean by a process of fermenting, which renders the proteid material very digestible. Soy-beans have not yet been introduced into this country, hence there will be little opportunity to use them, and they will, therefore, not be discussed here at length.
LEGUMES
Legumes are the seeds of a certain group of plants grown in pods. The term comes from a very ancient word, "legere," meaning to gather. Beans and peas are the most familiar types of this group.
Legumes rich in nitrogen
Legumes are rich in nitrogen, and some varieties are also very rich in oil. They are not equal to nuts in fuel or food value, however, because in the natural state they are hard, somewhat indigestible, and unpalatable. These qualities are due to the fact that the nitrogenous material of legumes are radically different from the nitrogen found in nuts, and belong to a class not so desirable as food. Meat may be omitted from the diet and legumes adopted as the chief source of nitrogen, but this change requires some knowledge and careful feeding in the beginning. Meat is digested wholly in the stomach and does not require mastication (only enough to be swallowed), while dried or mature legumes require much mastication, owing to the carbohydrates they contain. The best form in which legumes can be taken is in their green or immature state, owing to the fact that the immature starch they contain is readily soluble, while mature legume starch is rather difficult to digest.
FRUITS
The term "fruit" in a strictly botanical sense includes a very wide range of vegetable articles—the reproductive product of trees, or other plants, such as grains, legumes, nuts, berries, apples, peaches, plums, etc. In this lesson, however, I will apply the popular meaning to the term.
General composition of fruit
The common succulent or juicy fruits, including both tree fruits and berries, have many properties in common. The chemical composition of these typical fruits consists of from 80 to 85 per cent water, 5 to 15 per cent sugar, 1 to 5 per cent organic or fruit-acids, and small quantities of protein, cellulose, and the numerous salts, a portion of which may be combined with the fruit-acids. Some unripe fruits contain starch and various other carbohydrate substances, many of which are distasteful and unwholesome. On the other hand, when fruits become over-ripe, and decay sets in, the sugar is changed into carbon dioxid, alcohol, and acetic acid, and the fruit rapidly deteriorates in nutritive value and unwholesomeness. These changes, together with the loss of water, account for the sponginess and the tastelessness of cold storage and other long-kept fruits. All varieties of fruit are best when they have been allowed to ripen naturally on the trees, but modern commercial conditions demand that fruits for shipping purposes be picked slightly immature, and allowed to ripen in transit to the markets.
Dietetic value of fruits