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Boiling
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As applied to cooking, boiling
means cooking foods in boiling water. Water boils when its temperature
is raised by heat to what is commonly termed its boiling point.
This varies with the atmospheric pressure, but at sea level, under
ordinary
conditions, it is always 212 degrees Fahrenheit (100 degrees Celsius).
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. 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 sirups 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.
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