Class 8 Biology Microorganisms: Friend and Foe Food preservation techniques

Food preservation techniques

There are various techniques of food preservation like using chemicals, salt, vinegar, sugar, oil etc. Heat & cold treatment also helps to preserve food. Proper storage is very important for preservation of food.


Preserve by chemicals

Chemicals prevent attack & growth of microbes.  Some examples are as follows:


  • Sodium benzoate
    • Fruit juices, syrups, jams, jellies
  • Sodium metabishulphite
    • Dried fruits/ vegetables, syrups, fruit juices
  • Acetic acid (Vinegar)
    • Pickles, sauces, ketchup
  • Sodium chloride (Salt)
    • Meat, Amla, raw mango, fish
  • Oils
    • Ph is such that spoilage bacteria can’t survive
    • Fried food, pickles
  • Sugar
    • Reduce moisture content, therefore inhibit bacterial growth
    • Jam, Jelly, Squash



Food should be stored in proper sealed packets or air tight containers. Microbes need moisture, air etc. for growth. Therefore, such containers would inhibit their growth.


Preservation by Heat & Cold treatment


  • Food item can be heated to destroy micro-organisms that can otherwise spoil the food
  • An example of heat treatment is Sterilization.

Sterilization is a process in which food is heated to a high temperature (greater than 100oC) for a sufficient time. In this method, both the container & content are sterilized.

For example, Feeding bottles of babies are sterilized to keep it free from germs.


Not only heat, cold temperatures also prevent growth of spoilage bacteria. That is why, bread kept inside a refrigerator lasts longer than the one kept at room temperature.

Pasteurization is a technique that makes use of heat & cold treatments to preserve food items. In this process, milk is heated to about 700C for 15-30 sec & then suddenly chilled & stored. This technique was invented by Louis Pasteur (1864).

This technique destroys pathogens in milk, and reduces the number of spoilage microbes. Thus, it increases shelf life of milk.


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