Boiling, as it
applies to cooking, means cooking foods in boiling water.
In most populated parts of the world, plain water boils at
temperatures from about 200°F to 212°F (95°C to 100°C).
This varies with the atmospheric pressure, which in turn
varies with both altitude and weather. When the
atmospheric pressure on the surface of the water is
lessened, boiling takes place at a lower temperature than
that mentioned, and in extremely high altitudes the
boiling point is so lowered that to cook certain foods by
means of boiling water is difficult.
As the water heats in the
process of boiling, tiny bubbles appear on the bottom of
the vessel in which it is contained and rise to the
surface. Then, gradually, the bubbles increase in size
until large ones form, rise rapidly, and break, thus
producing constant agitation of the water.
Boiling has various
effects on foods. It toughens the albumin in eggs,
toughens the fiber and dissolves the connective tissues in
meat, softens the cellulose in cereals, vegetables, and
fruits, and dissolves other substances in many foods. A
good point to bear in mind in preparing foods by boiling
is that slowly boiling water has the same temperature as
rapidly boiling water and is therefore able to do exactly
the same work.
Turning the stove on
high, keeping the gas burning full heat, or running the
fire hard to keep the water boiling rapidly is therefore
unnecessary; besides, it wastes fuel without doing the
work any faster and sometimes not so well. However, there
are several factors that influence the rapidity with which
water may be brought to the boiling point; namely, the
kind of utensil used, the amount of surface exposed, and
the quantity of heat applied.
A cover placed on a
saucepan or a kettle in which food is to be boiled retains
the heat, and thus causes the temperature to rise more
quickly; besides, a cover so used prevents a loss of water
by condensing the steam as it rises against the cover. As
water boils, some of it constantly passes off in the form
of steam, and for this reason syrups or sauces become
thicker the longer they are cooked. The evaporation takes
place all over the surface of the water; consequently, the
greater the surface exposed, the more quickly is the
quantity of water decreased during boiling.
Another point to observe
in the boiling process is that foods boiled rapidly in
water have a tendency to lose their shape and are reduced
to small pieces if allowed to boil long enough.
Besides serving to cook
foods, boiling also renders water safe, as it destroys any
germs that may be present. This explains why water must
sometimes be boiled to make it safe for drinking. Boiled
water, as is known, loses its good taste. However, as this
change is brought about by the loss of air during boiling,
the flavor can be restored and air again introduced if the
water is shaken in a partly filled jar or bottle, or
beaten vigorously for a short time with an egg beater.