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.

24. 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.

25. 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.