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The Epic Interactive Encyclopedia 1998
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Epic Interactive Encyclopedia, The - 1998 Edition (1998)(Epic Marketing).iso
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Food_technology
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INFOTEXT
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1992-09-03
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The application of science to the commercial
processing of foodstuffs. Food is processed
to render it more palatable or digestible, or
to preserve it from spoilage. Food spoils
because of the action of enzymes within the
food that change its chemical composition, or
because of the growth of bacteria, moulds,
yeasts, and other microorganisms. Fatty or
oily foods also suffer oxidation of the fats,
giving them a rancid flavour. Traditional
forms of processing include boiling, frying,
flour-milling, bread-making, yoghurt- and
cheese-making, brewing, and various methods
of food preservation, such as salting,
smoking, pickling, drying, bottling, and
preserving in sugar. Modern food technology
still employs traditional methods but also
uses many novel processes and additives,
which allow a wider range of foodstuffs to be
preserved. Refrigeration below 5 degrees C/41
degrees F (or below 3 degrees C/37 degrees F
for cooked foods) slows the processes of
spoilage, but is less effective for foods
with a high water content. Although a
convenient form of preservation, this process
cannot kill microorganisms, nor stop their
growth completely, and a failure to realize
its limitations causes many cases of food
poisoning. Refrigerator temperatures should
be checked as the efficiency of the machinery
(see refrigeration) can decline with age, and
higher temperatures are dangerous. Deep
freezing (-18 degrees C/-1 degrees F or
below) stops almost all spoilage processes,
although there may be some residual enzyme
activity in uncooked vegetables, which is why
these are blanched (dipped in hot water to
destroy the enzymes) before freezing.
Microorganisms cannot grow or divide, but
most remain alive and can resume activity
once defrosted. Some foods are damaged by
freezing, notably soft fruits and salad
vegetables, whose cells are punctured by ice
crystals, leading to loss of crispness. Fatty
foods such as cow's milk and cream tend to
separate. Various processes are used for deep
freezing foods commercially. Pasteurization
is used mainly for milk. By holding the milk
at a high temperature, but below boiling
point, for a period of time, all
disease-causing bacteria can be destroyed.
The milk is held at 72 degrees C for 15
seconds. Other, less harmful bacteria
survive, so the milk will still go sour
within a few days. Boiling the milk would
destroy all bacteria, but impair the flavour.
Ultra-heat treatment is used to produce UHT
milk. This process uses higher temperatures
than pasteurization, and kills all bacteria
present, giving the milk a long shelf life
but altering the flavour. Drying is an
effective method of preservation because both
microorganisms and enzymes need water to be
active. Products such as dried milk and
instant coffee are made by spraying the
liquid into a rising column of dry, heated
air. Freeze-drying is carried out under
vacuum. It is less damaging to food than
straight dehydration in the sense that foods
reconstitute better, and is used for quality
instant coffee and dried vegetables. Canning
relies on high temperatures to destroy
microorganisms and enzymes. The food is
sealed into a can to prevent any
recontamination by bacteria. Beverages may
also be canned to preserve the carbon dioxide
that makes drinks fizzy. Pickling utilizes
the effect of acetic acid, found in vinegar,
in stopping the growth of moulds. In
sauerkraut, lactic acid, produced by
bacteria, has the same effect. Similar types
of non-harmful, acid-generating bacteria are
used to make yoghurt and cheese. Curing of
meat involves soaking in salt (sodium
chloride) solution, with saltpetre (sodium
nitrate) added to give the meat its pink
colour and characteristic taste. Saltpetre (a
preservative was originally included by
chance because it was a natural contaminant
of rock salt. The nitrates in cured meats are
converted to nitrites and nitrosamines by
bacteria, and these are potentially
carcinogenic to humans. Of all the additives
in use, the time-honoured nitrates are among
the most dangerous. Irradiation is a method
of preserving food by subjecting it to
low-level radiation. It is highly
controversial (see food irradiation) and not
yet widely used in the UK. Puffing is a
method of processing cereal grains. They are
subjected to high pressures, then suddenly
ejected into a normal atmospheric pressure,
causing the grain to expand sharply. This
type of process is used to make puffed wheat
cereals and puffed rice cakes. Chemical
treatments are widely used, for example in
margarine manufacture, where hydrogen is
bubbled through vegetable oils in the
presence of a catalyst to produce a more
solid, spreadable fat. The catalyst is later
removed. Chemicals that are introduced in
processing and remain in the food are known
as food additives and include flavourings,
preservatives, antioxidants, emulsifiers, and
colourings.