This change can be easily observed in the
case of peas. As is well known, young green peas are rather sweet
because of the sugar they contain, while mature or dried peas have lost
their sweetness and are starchy. The sugar that is found in large
quantities in such vegetables as peas, carrots, turnips, etc. is largely
cane sugar. The starch that vegetables contain occurs in tiny granules,
just as it is found in cereals, and is affected by cooking in the same
way. The mature vegetables in which the starch has developed, although
less tender and less sweet than young ones, have a higher food value. In
fact, the carbohydrate that vegetables contain constitutes a large
proportion of their food value.
One of the chief sources of starch among vegetables is the potato, in
which the starch grains are large and, if properly cooked, easily
digested. Irish, or white, potatoes contain very little carbohydrate in
the form of sugar, but in the sweet potato much of the carbohydrate is
sugar. In either of these two forms--starch and sugar--vegetable
carbohydrate is easily digested.
15. MINERAL MATTER, OR ASH, IN VEGETABLES.--The mineral matter in
vegetables is found in comparatively large quantities, the average
amount being slightly over 1 per cent. The presence of this substance is
of great value, because the mineral salts of both fruits and vegetables
are essential in the diet of adults in order to keep their health in a
normal condition. The mineral salts of vegetables render the blood more
alkaline instead of more acid, as do those contained in cereals and
meat.
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