Pasteurization
This method was discovered by famous biologist,
Louis Pasteur. By this method milk is prevented from turning sour. In this
process, milk is heated to 71 C for a few seconds and then cooled rapidly. This
kills most of the bacteria. The bacteria which survive this treatment may
become retarded in growth. In this way, the milk is preserved for a few days.
Refrigeration
In this methods, food is kept at very low
temperature usually below freezing point. It retards the action of enzymes and
the growth of bacteria. In deep freezers food can be preserved for many years.
Quick freezing helps to maintain the taste and texture of meat, fruit and
vegetables.
Dehydration
In this method food is dried. Such food can be kept
safe for a long period at normal temperature. Bacteria do not grow without
water, therefore when water content is removed from meat and vegetables, they
can be preserved for long durations. Pickling of food is another common
indigenous technology in which taste and texture of pickled food is maintained
for long.
Canning
In this method the food is first heated at a high
temperature. This kills bacteria and destroys enzymes. Then, the food is sealed
in a metallic container. In this way; food becomes safe from contamination.
Metallic cans are usually lacquered to prevent food from chemically reacting
with metals and producing toxic substances
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