EFFECT OF COOKING ON FRUIT

As has been explained, sugar is the food material from which the nutritive value of fruits is obtained. With the exception of a few predigested foods, manufactured in such a way that they can be digested easily, this sugar is probably the most easily digested form of food that can be obtained.

This substance, being held in solution in the fruit juices, which are encased in a cellulose covering, depends to some extent for its digestion on the hardness of the cellulose. When this covering is old and hard or green and tough, as the case may be, it is difficult for the digestive juices to break through and attack the sugar contained inside.

As this difficulty is not encountered when fruit is fresh and ripe, its freshness and ripeness become important factors in digestibility. Cooking is also an important factor because it softens the cellulose, but there are certain other changes made by cooking that must be taken into consideration as well.

EFFECT OF COOKING ON FRUIT.--Cooking affects fruits in numerous ways, depending on the condition of the fruit itself, the method used, and the length of time the heat is applied. When fruits are cooked in water or in a thin sirup, the cellulose becomes softened.

On the other hand, if they are cooked in a heavy sirup, as, for instance, in the making of preserves, the cellulose becomes hardened and the fruit, instead of breaking up, remains whole or nearly so and becomes tough and hard in texture. The addition of quantities of sugar, as in the latter case, besides helping to keep the fruit whole, increases its food value.

Another change that usually takes place when fruit is cooked is in its flavor. This change is due either to an increase in the acid contained in the fruit or to a decrease in the amount of sugar.

Some authorities believe that cooking increases the amount of acid, while others hold the view that, when fruit is cooked without removing the skins and seeds, the acid contained in the seeds and skins and not noticeable when the fruit is fresh, is released during the cooking.

Such is undoubtedly the case with plums. The change that is brought about in the sugar by the cooking of fruits consists in changing the cane sugar into levulose and dextrose, which are not so sweet. This change accounts for the fact that some cooked fruits are less sweet than others, in spite of the fact that the acid does not seem to be increased.

In addition to producing certain changes in fruit, cooking, if done thoroughly, renders fruits sterile, as it does other foods; that is, it kills any bacteria that the fruits may contain. Advantage of this fact is taken when fruits are canned for future use.

Although most persons prefer raw fruit to that which is cooked, there are some who object to eating this food raw, but who are not always certain as to the reason for their objection. Like other raw foods, fruits in their fresh state contain vitamines; that is, a substance that helps to keep the body in a healthy, normal condition.

These are found to some extent in cooked fruits, but not in the same quantity as in raw ones; consequently, as much use as possible should be made of raw fruits in the diet.