14. In fruits that are not fully matured, or, in other words, green
fruits, the sugar has not developed to so great an extent as it has in
perfectly ripe fruits. Consequently, such fruits are not so high in food
value as they are when they become ripe. As is well known, it is the
sugar of fruits that accounts for their sweet taste, for the sweeter the
fruits, the more sugar and the less acid they contain. The quantity of
this substance varies from 1 per cent. in lemons to 20 per cent. in some
other fresh fruits, such as plums. In dried fruits, the amount of sugar
is much higher, reaching as high as 60 per cent. or even more in such
fruits as figs, dates, and raisins.

15. 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