126. Starch, dextrin, and caramel. — Starch, heated dry,
changes to dextrin, which is soluble in cold water. In
browned flour part of the starch has undergone this change,
lessening the thickening property of the flour, and at the
same time part of the dextrin has been further changed to
caramel, which causes the brown color. The inside of baked
potatoes is partially dextrinized, and the crust under the
skin is largely caramel and dextrin. It is the presence of
these soluble substances that makes baked potatoes more
easily digestible than boiled ones. A temperature of 320° F.
is required to dextrinize starch. Explain wdiy dextrin is
not formed in boiled potatoes.
127- Experiments in heating starch dry. — A. Heai about one
tablespoonful of starch in a test-tube (or on a small tin pan kept
for use in experiments). When brown, take out part of it and test
it for starch, (1) by heating with water, (2) by adding iodine.
B. Continue to heat the rest of the starch in a test-tube, until
black. What is the black substance? What do you observe on
the sides of the test-tube ?
128. Composition of starch. — Starch is composed of
carbon, oxygen, and hydrogen. When heated, the two
last pass off as water, leaving the carbon.
FUEL FOODS: SOME STARCHY PLANTS 71
129. Digestion of starch. — Digestion is a process of
solution. Saliva begins the digestion of starch by
changing some of it first into soluble starch, and then
into a sugar called maltose. Starch digestion is com-
pleted in the small intestine.
A substance in saliva, called ptyalin, causes this change.
(§ 230.) The test for maltose is Fehling's solution/ which
combines with it to form a reddish or orange-colored sub-
stance.
Experiments to show the action of saliva on starch. ^ — A. Make
a thin starch paste (about one-half teaspoonful of starch to three
or four tahlespoonfuls of water). Divide this between two test-
tubes ; in a third collect some saliva. Pour part of the saliva into
one of the tubes of starch paste. Add a few drops of Fehling's
solution to (1) the saliva, (2) the starch, (3) a portion of the mix-
ture of saliva and starch. Do any of these change color? Does
either saliva or starch alone contain maltose? Explain the pres-
ence of this sugar in the mixture of starch and saliva.
B. At the end of fifteen minutes, test the mixture for starch
with iodine. A violet or a red color shows that the starch is par-
tially changed to sugar. Is the action of saliva on starch chemical
or physical ? The action of the sugar on Fehling's solution ?
Starch as Fuel for the Body
130. The work of the body. — How does eating help
to keep us alive ? Life involves activity ; work, play,
activity of any sort, makes us hungry ; food gives us
energy to go on working and playing. Any activity
1 A mixture of copper sulphate and caustic potash.
2 Precaution. — Test starch for sugar before adding saliva. Some
starches are mixed with a little sugar. Cornstarch and starch pre-
pared from hominy are usually pure. For best results, keep the
tubes standhig in lukewarm water (98° F.).
72 THEORY AND PRACTICE OF COOKERY
that uses up energy is, in the scientific sense, work.
Your muscles work as hard in playing a game as in
going on an errand, and just as truly does the heart
work in pumping blood, the stomach in digesting food,
the brain and nerves in giving rise to thought and
feeling.
Page 35
Presented as published in 1901. Historical recipes may not meet modern food-safety standards. Cook from the modern interpretation, not the original instructions.
AI-modernized reading of the original text
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126. Starch, dextrin, and caramel. — Starch, heated dry,
changes to dextrin, which is soluble in cold water. In
browned flour part of the starch has undergone this change,
lessening the thickening property of the flour, and at the
same time part of the dextrin has been further changed to
caramel, which causes the brown color. The inside of baked
potatoes is partially dextrinized, and the crust under the
skin is largely caramel and dextrin. It is the presence of
these soluble substances that makes baked potatoes more
easily digestible than boiled ones. A temperature of 320° F.
is required to dextrinize starch. Explain wdiy dextrin is
not formed in boiled potatoes.
127- Experiments in heating starch dry. — A. Heai about one
tablespoonful of starch in a test-tube (or on a small tin pan kept
for use in experiments). When brown, take out part of it and test
it for starch, (1) by heating with water, (2) by adding iodine.
B. Continue to heat the rest of the starch in a test-tube, until
black. What is the black substance? What do you observe on
the sides of the test-tube ?
128. Composition of starch. — Starch is composed of
carbon, oxygen, and hydrogen. When heated, the two
last pass off as water, leaving the carbon.
FUEL FOODS: SOME STARCHY PLANTS 71
129. Digestion of starch. — Digestion is a process of
solution. Saliva begins the digestion of starch by
changing some of it first into soluble starch, and then
into a sugar called maltose. Starch digestion is com-
pleted in the small intestine.
A substance in saliva, called ptyalin, causes this change.
(§ 230.) The test for maltose is Fehling's solution/ which
combines with it to form a reddish or orange-colored sub-
stance.
Experiments to show the action of saliva on starch. ^ — A. Make
a thin starch paste (about one-half teaspoonful of starch to three
or four tahlespoonfuls of water). Divide this between two test-
tubes ; in a third collect some saliva. Pour part of the saliva into
one of the tubes of starch paste. Add a few drops of Fehling's
solution to (1) the saliva, (2) the starch, (3) a portion of the mix-
ture of saliva and starch. Do any of these change color? Does
either saliva or starch alone contain maltose? Explain the pres-
ence of this sugar in the mixture of starch and saliva.
B. At the end of fifteen minutes, test the mixture for starch
with iodine. A violet or a red color shows that the starch is par-
tially changed to sugar. Is the action of saliva on starch chemical
or physical ? The action of the sugar on Fehling's solution ?
Starch as Fuel for the Body
130. The work of the body. — How does eating help
to keep us alive ? Life involves activity ; work, play,
activity of any sort, makes us hungry ; food gives us
energy to go on working and playing. Any activity
1 A mixture of copper sulphate and caustic potash.
2 Precaution. — Test starch for sugar before adding saliva. Some
starches are mixed with a little sugar. Cornstarch and starch pre-
pared from hominy are usually pure. For best results, keep the
tubes standhig in lukewarm water (98° F.).
72 THEORY AND PRACTICE OF COOKERY
that uses up energy is, in the scientific sense, work.
Your muscles work as hard in playing a game as in
going on an errand, and just as truly does the heart
work in pumping blood, the stomach in digesting food,
the brain and nerves in giving rise to thought and
feeling.