A)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 meta bisulphite are common preservatives
1)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 amla, raw mangoes, tamarind, etc.
2) 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.
3)Preservation by Oil and Vinegar
Use of oil and vinegar prevents spoilage of pickles because bacteria cannot live in such an environment. Vegetables,
fruits, fish and meat are often preserved by this method.
B) Heat and Cold Treatments
boiling milk before it is stored or used. Boiling kills many microorganisms.
Similarly, we keep our food in the refrigerator. Low temperature inhibits the growth of microbes.