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Food Preservation

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Food Preservation - Lesson Summary

Food poisoning
An undesirable change in colour,  odour and taste in food brought about by microorganisms is called as food poisoning.  Food poisoning may cause infection, serious illness and even death. Food has to be preserved in order to prevent it from being contaminated by microorganisms.

Characteristics of spoilt food
Food contaminated by bacteria or other microorganisms is unfit for consumption. This contaminated food is called as spoilt food. We can detect spoilt food by change in colour, stickiness, bad odour and bad taste.

Favourable conditions for microbial growth
Conditions required for growth of microorganisms are termed to be favourable conditions. These are specified below.

Food preservation
The process of treating food in order to slow down spoilage is called as food preservation.

Methods of food preservation

a) Chemical method of preservation is done by adding certain chemicals which have the capability of preserving the food. Preservatives include sodium benzoate and sodium metabisulphite used in jams and squashes. 

b) Preservation by vinegar is done by adding vinegar as microorganisms cannot live in sour environment provided by the same.

c) Preservation by sugar is done by adding sugar which reduces moisture in food. It also inhibits the growth of microbes that spoil food. Jams, jellies and squashes are preserved using sugar.

d) Preservation by oil is done by adding oil, as bacteria and fungi cannot live in an environment provided by oil.

e) Sun drying is one another method of preserving food. Food like vegetables and fruits are sliced and sundried in order to remove moisture from them. These dehydrated food products can be stored and preserved.

f) Salting is done by using common salt. Sodium chloride used as common salt absorbs moisture from food, making it dry and uninhabitable for microbes.

g) Pasteurisation is a method of preserving milk. Louis Pasteur discovered the process of pasteurisation. During pasteurisation, milk is first heated to about 70 degrees Celsius for 15 to 30 seconds and then suddenly chilled. Sudden chilling of milk is done to prevent the growth of microbes.

h) Boiling and freezing are the two other methods used to preserve food. Deep freezing directly prevents the bacterial growth as many bacteria cannot sustain their life below zero degree Celsius.

i) Bottling and canning is a method of preserving drinks, colas, beverages and other products which are to be stored under low temperatures. Carbon dioxide is added as a preservative in some cool drinks. Some edible foods like fish, meat are canned in air tight containers for preservation. 


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