USES OF STARCH
“That jelly,” remarked Jules, “looks just like the paste that I make
with laundry starch. Your potato starch there in the bottom of the
glass has exactly the same appearance as starch dissolved in cold water
for ironing clothes.”
“That close resemblance,” replied his uncle, “is explained by the fact
that potato starch and laundry starch are at bottom the same thing.
Both substances are chemically known as fecula; but laundry starch is
made from cereals, particularly wheat, while fecula, properly speaking,
comes either from potatoes or from various grains and roots.
“Like the starch of the potato, laundry starch is in the form of
superposed leaflets, but its grains are much smaller: ten thousand
would hardly be enough to make a pellet the size of a pin’s head. And
there are some still smaller. It would take sixty-four thousand grains
of Indian corn starch to make a pin’s head or, to be more exact, to
fill the inside of a cube measuring one millimeter on a side; and in
the case of the beet it would take ten millions. You see that in spite
of their excessive smallness, a smallness that makes them invisible to
the naked eye, the starch grains of the potato are giants in
comparison.
“It is chiefly by the varying size of their microscopic grains that the
starches of different kinds are distinguished from one another. In
substance and structure they are all alike. Placed in warm water, their
grains swell, burst, expand their leaflets, and the starch, from
whatever source, is changed into a glutinous jelly.
“Starch is the food supply of plant-life. Wherever we find buds that
are intended to develop by themselves, wherever we find germs, there
also we shall find a supply of starch serving as a sort of food
reserve. Hence this peculiar provision is met with in tubers, bulbs,
bulblets, seeds, and fleshy roots. Now when these buds and germs
develop, the starch becomes, in the process of vegetation, a kind of
sugar which, being soluble in water, can be sent to all parts of the
young plant and serve it for food.
“By certain artificial devices this same change of starch into sugar
can be brought about. The simplest of these devices is the application
of heat, which always enters into the preparation of farinaceous food.
Let us take a few examples. A raw potato is uneatable. Boiled in water
or roasted in the ashes, it is excellent. What has happened, then? Heat
has converted a part of the starch into sugar, and the tuber has become
a sugary farinaceous paste. The same can be said of the chestnut. Raw,
it is no great delicacy, although at a pinch it can be eaten; cooked,
it is worthy of all the praise we can give it. I appeal to you to back
me up in this assertion. Here, then, we have another transformation of
starch into sugar by the action of heat. Beans, peas, both as hard as
bullets in the dry state and of no agreeable flavor, are unmistakably
sweetened by being boiled in water and having their starch acted on by
heat. Our various farinaceous foods behave in the same way. Ingenuity
brings into play a more powerful agent than heat alone to convert the
starch into sugar. It is boiled in water and during the boiling a
little sulphuric acid or oil of vitriol is added. Under the influence
of this energetic fluid the starch is changed into a sugary syrup. It
is of course to be understood that this syrup, as soon as it has been
thus produced, is separated from the oil of vitriol which has served to
make it.
“The sugar thus obtained is a soft, sticky substance, and almost as
sweet as honey, but very different from ordinary sugar, which is solid
and comes in beautiful white loaves. [3] It is called starch-sugar or
glucose. Confectioners use it a great deal. When you crunch a
sugar-plum—and I am persuaded that you do not underestimate the
excellence of sugar-plums—do you know what you are eating? A
composition of starch and starch-sugar. I pass over the almond in the
center; that is beside the question.”
“Do you mean to say,” demanded Jules, “that a bag of sugar-plums comes
from such stuff as potatoes and oil of vitriol?”
“Such is undoubtedly the origin of the delicious sugar-plum,” was the
reply; “and indeed many of the delicacies of the pastry-cook, of the
confectioner, and of the manufacturer of refreshing beverages, which
you believe to be sweetened with ordinary sugar, really owe their sweet
taste to syrup made from starch—a much cheaper product than sugar. You
see the potato furnishes something else besides the modest dishes with
which it supplies our table.
“Nor is that the whole story. Starch-sugar, or glucose, is exactly the
same as the sugar of ripe grapes. With potato-flour, water, and a few
drops of oil of vitriol there is artificially produced, in enormous
boilers, the same sugary substance that the vine produces in its
bunches of grapes with the help of the sun’s rays. Now grape sugar
turns to alcohol by fermenting. Glucose must undergo a similar change.
And, as a matter of fact, in northern countries too cold to admit of
the cultivation of the vine, alcoholic liquors are made from starch
previously changed into sugar. On account of their origin these liquors
go under the general name of potato-brandy. All seeds and roots rich in
starch can be used in similar manufacture.
“Beer is a product of this sort. First barley is made to germinate by
being kept moist and warm. In the process of germination the starch is
changed into glucose for the nourishment of the young shoots. When the
little plants begin to develop, the grain is dried and ground to flour.
This mixed with water furnishes a sugary liquid which ferments, turning
partly to alcohol and finally becoming beer.”