Effects of alkalies, acids, and calcium on the structural or
woody part of fruits and vegetables. Ammonia and sodium bicar-
bonate added to the water in which vegetables are boiled, or ammonia or
ammonium carbonate added to water in which vegetables are steamed,
causes them to soften in a shorter time than if these substances had not
been added. With longer cooking the vegetable becomes mushy and dis-
integrates. The disintegration begins with the surface layer of the food,
and its depth depends on the length of time of cooking and the size of
the piece of food.
130 FRUITS AND VEGETABLES
If vinegar is added to the water in which vegetables are cooked the
effect is opposite from that of sodium bicarbonate : a firmer and more solid
texture is obtained and the vegetable requires longer to cook. In cooking
vegetables like cabbage and spinach the amount of calcium and magnesium
salts found in the water seems to have little effect upon the texture or the
length of time for cooking.
The pulp and white part of the rind of watermelon as well as the pulp
of muskmelon or cantaloupe, and perhaps other foods, can be made very
firm and brittle or woody if soaked in saturated calcium hydroxide (lime)
water. The longer they are soaked the harder and firmer they become if
the water is kept saturated with lime. Five to six hours' soaking is usually
sufficient to produce enough firmness to prevent shriveling when cooked
in sirups for preserves or pickle. The melon pulp may be cooked in water
until transparent and tender, then put in lime water to harden, and finally
cooked in a sirup. Or cooking first in only water does not prevent harden-
ing of the pulp by calcium. The few times that cucumbers have been soaked
in lime water either slight or no hardening occurred. But other calcium
compounds such as calcium chloride do produce hardening in pickles.
Pickles. Cucumber pickles are seldom made in class work; but why
brined pickles spoil is a perennial question. Rahn has offered a solution of
the difficulty. An abstract of his work follows.
The inside of the cucumber is free of bacteria, but the brine into which
the cucumbers are placed contains several thousand bacteria per cubic
centimeter. There are many different kinds of bacteria present in the
beginning but with the strength of brine maintained most of them die.
However, a few kinds that thrive in the brine survive. Fresh brine con-
tains no food for bacteria. But with placing of the pickles in brine, or the
formation of brine by adding dry salt to cucumbers, small amounts of
sugar and other bacterial food are dissolved from the cucumbers as they
shrink. Hence bacteria that can tolerate salt grow and decompose the sugar.
The resulting decomposition products of the sugar are acid and gas. The
gas produces froth. The acid, probably mostly lactic, is very important,
for the keeping of the pickles depends upon it. The concentration of the
acid is rather high when frothing ceases, varying from 0.6 to 1.2 per cent.
The acid is a fairly good disinfectant and practically all bacteria in the
brine are killed.
Page 104
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Effects of alkalies, acids, and calcium on the structural or
woody part of fruits and vegetables. Ammonia and sodium bicar-
bonate added to the water in which vegetables are boiled, or ammonia or
ammonium carbonate added to water in which vegetables are steamed,
causes them to soften in a shorter time than if these substances had not
been added. With longer cooking the vegetable becomes mushy and dis-
integrates. The disintegration begins with the surface layer of the food,
and its depth depends on the length of time of cooking and the size of
the piece of food.
130 FRUITS AND VEGETABLES
If vinegar is added to the water in which vegetables are cooked the
effect is opposite from that of sodium bicarbonate : a firmer and more solid
texture is obtained and the vegetable requires longer to cook. In cooking
vegetables like cabbage and spinach the amount of calcium and magnesium
salts found in the water seems to have little effect upon the texture or the
length of time for cooking.
The pulp and white part of the rind of watermelon as well as the pulp
of muskmelon or cantaloupe, and perhaps other foods, can be made very
firm and brittle or woody if soaked in saturated calcium hydroxide (lime)
water. The longer they are soaked the harder and firmer they become if
the water is kept saturated with lime. Five to six hours' soaking is usually
sufficient to produce enough firmness to prevent shriveling when cooked
in sirups for preserves or pickle. The melon pulp may be cooked in water
until transparent and tender, then put in lime water to harden, and finally
cooked in a sirup. Or cooking first in only water does not prevent harden-
ing of the pulp by calcium. The few times that cucumbers have been soaked
in lime water either slight or no hardening occurred. But other calcium
compounds such as calcium chloride do produce hardening in pickles.
Pickles. Cucumber pickles are seldom made in class work; but why
brined pickles spoil is a perennial question. Rahn has offered a solution of
the difficulty. An abstract of his work follows.
The inside of the cucumber is free of bacteria, but the brine into which
the cucumbers are placed contains several thousand bacteria per cubic
centimeter. There are many different kinds of bacteria present in the
beginning but with the strength of brine maintained most of them die.
However, a few kinds that thrive in the brine survive. Fresh brine con-
tains no food for bacteria. But with placing of the pickles in brine, or the
formation of brine by adding dry salt to cucumbers, small amounts of
sugar and other bacterial food are dissolved from the cucumbers as they
shrink. Hence bacteria that can tolerate salt grow and decompose the sugar.
The resulting decomposition products of the sugar are acid and gas. The
gas produces froth. The acid, probably mostly lactic, is very important,
for the keeping of the pickles depends upon it. The concentration of the
acid is rather high when frothing ceases, varying from 0.6 to 1.2 per cent.
The acid is a fairly good disinfectant and practically all bacteria in the
brine are killed.