CELLULOSE IN FRUIT

CELLULOSE IN FRUIT.--In fruits, as in vegetables, cellulose is found in varying quantities. The larger the quantity, the lower will be the food value of the fruit, except where the water has been evaporated, as in the case of dried fruits.

The digestibility of this cellulose, however, is not worth considering, for, while it is possible that small amounts of very young and tender cellulose from fruits may be digested, on the whole this characteristic may be disregarded. The skins and seeds of fruits, as well as the coarse material that helps to make up the pulp, are known as refuse and are treated as such by the human digestive tract; but it is to this waste material, or cellulose, that the laxative quality of fruit is largely due.

In cases where there are digestive or intestinal troubles, it is often necessary to remove the cellulose before the fruit is eaten. The coarse material may be removed and that which is more tender may be broken up by pressing the fruit through a sieve or a strainer of some kind.

The cooking of fruits is another means of making the cellulose in them more easily digested, for it softens, or disintegrates, the various particles of the indigestible material. When fruit is taken for its laxative effect and the irritation of the cellulose needs no consideration, the skins of the fruits may be eaten instead of being rejected. However, to avoid any trouble, they should be well chewed.

Minerals in Fruit.--All fruits contain a certain percentage of mineral salts. The quantity varies in the different kinds of fruits, but it averages about 1 per cent.

These salts have the opposite effect on the blood from those found in meats and cereals, but they act in much the same way as the minerals of vegetables. In other words, they have a tendency to render the blood more alkaline and less acid.

They are therefore one of the food constituents that help to make fruit valuable in the diet and should be retained as far as possible in its preparation. In fact, any method that results in a loss of minerals is not a good one to adopt in the preparation of fruits.

The minerals commonly found in fruits are iron, lime, sodium, magnesium, potash, and phosphorus. These are in solution in the fruit juices to a very great extent, and when the juices are extracted the minerals remain in them.

Acids in Fruit.--Some fruits contain only a small amount of acid, while others contain larger quantities. It is these acids, together with the sugar and the volatile oils of fruits, that constitute the entire flavor of this food. Most ripe fruits contain less acid than unripe ones, and cooked fruits are often higher in acid than the same fruits when raw.

Numerous kinds of acid are found in the different varieties of fruits. For example, lemons, oranges, grapefruit, and a few other fruits belonging to the class known as citrus fruits contain citric acid; peaches, plums, apricots, and apples, malic acid; and grapes and many other fruits, tartaric acid.