The common methods of preserving food in our homes-
Chemical method
Salts and edible oils are the common chemicals generally used to check the growth of microorganisms.Therefore they are called preservatives.We add salt or acid preservatives to pickles to prevent the attack of microbes.Sodium benzoate and sodium metabisulphite are common preservatives.
Preservation by Common salt
Common salt has been used to preserve meat and fish for ages.Meat and fish are covered with dry salt to check the growth of bacteria.Salting is also used to preserve am-la,raw mangoes,tamarind,etc.
Preservation by Sugar
Jams,jellies and squashes are preserved by sugar.Sugar reduces the moisture content which inhibits the growth of bacteria which spoil food.
Preservation by Oil and Vinegar
Use of oil and vinegar prevents spoilage of pickles because bacteria cannot live in such as environment.Vegetables,fruits,fish and meat are often preserved by this method.
Heat and Cold Treatments
Boiling kills many microorganisms.Similarly,we keep our food in the refrigerator.Low temperature inhibits the growth of microbes.
Pasteurized milk can be consumed without boiling as it is free from harmf microbes.The milk is heated to about 70^0C for 15–30 seconds and then suddenly chilled an stored. By doing so,it prevents the growth of microbes.This process is known as Pasteurisation.
Storage and Packing
These days dry fruits and even vegetables are sold in sealed air tight packets to prevent the attack of microbes.