10. While fruit is usually improved by cultivation, there has been a tendency through this means to produce fruits that will stand up for long periods of time, so that they may be marketed at great distances from the place where they are grown. For instance, apples, especially those found in the market in the spring, and other fruits, which look very fine, will many times be found to have a tough skin and to be almost tasteless.
In general, fruits of delicate flavor and texture cannot be kept very long after they have ripened. To stand shipping, they must be picked in their green stage; then if they are kept in the right temperature they will ripen after picking. Bananas that are to be shipped a long distance are picked when perfectly green, but by the time the consumer buys them they are usually well ripened. In addition to bananas, a few other tropical fruits are shipped out of their native climates in small numbers and are sold at very high prices. However, many tropical fruits cannot be shipped to the Northern States because of their perishable nature.
COMPOSITION AND FOOD VALUE OF FRUITS
COMPOSITION OF FRUITS
11. The composition of fruits is a matter of considerable importance, for on it the food value of the fruits depends. To a certain extent, the composition of all fruits is the same, but the varieties of this food differ in their food values almost as greatly as do vegetables. Many of them are extremely low in this respect, while a few of them are rather high. In order to determine the place that fruit should have in a meal, it is necessary to obtain a definite idea of the composition as well as the food value of the different varieties.
12. PROTEIN AND FAT IN FRUITS.--Such small quantities of protein and fat are contained in fruits that very little attention need be given to these substances. Exceptions are found in avocados, or alligator pears, and in ripe olives, both of which are high in fat. Then, too, there is a small amount of protein in grapes and some other fruits, but it is not sufficient to merit consideration.
13. CARBOHYDRATE IN FRUIT.--Whatever food value fruits may have, whether it be high or low, is due to the carbohydrate they contain. Some green fruits and bananas contain a very small amount of starch, but on the whole the carbohydrate of fruits is in the form of sugar and is in solution in the fruit juices. The chief form of this carbohydrate is known as levulose, or fruit sugar. However, glucose, another form of sugar, is also found in nearly all fruits, grapes and dried fruits, such as figs, raisins, etc., containing an unusually large amount. In addition, cane sugar is contained in the majority of fruits. Pectin is also a carbohydrate that is found in large quantities in some fruits, while in other fruits it is lacking. This substance is related to the gums and to cellulose. Although it is one of the carbohydrates from which no food value is derived, it is of considerable importance, because it is responsible for the jelly-making properties of fruits.
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.