This document discusses various techniques for food preservation, including thermal processing (e.g. pasteurization), cold processing (e.g. chilling, freezing), controlling water content through dehydration, and using preservatives. Thermal processing involves heating food to temperatures above 82°C to kill microorganisms. Cold processing slows microbial growth by subjecting food to low temperatures around 0°C. Controlling water content through dehydration removes water needed by microorganisms to grow. Preservatives like salt, sugar, and chemicals inhibit microbial growth.

1. Vigyan Ashram Pabal

2. Techniques of Food Preservation
Food Preservation Techniques
Thermal
Cold Processing Controlling Water
Chemicals
Chilling
Pasteurization
Dehydration
Preservatives

3. Thermal Processing Method
This process of food preservation is related with heating the
food product. This process is also known as heat treatment
of food product
Heating is done in range of 85 to 90 deg celcius for some
time
Examples:-
- Pasteurization of milk
- Dipping of vegetables in boiling water for some time
Advantages
- Microorganisms like bacteria are killed at temperatures
above 82 deg celcius

4. Removal of heat(Cold Processing)
The Food product is subjected to Low temperature
around 0 degree Celsius
This process can be done through chilling , freezing
using refrigerator,
Advantages
Microbial growth is slowed down
Storage life of food product is increased
Examples
Ice-cream , Cheese

5. Control of Water
In this process, the food product is subjected to dryers
By this process, water is removed from the food product
Advantages
- Microorganisms need water for biochemical reactions
hence if water is removed, microorganisms will not grow
on food product
- By this process ,microorganisms don’t get free water thus
growth of microorganisms is stopped
Examples
Use of Dryers for preparing mango powder, dried vegetables

6. Preservatives
They contain a certain chemical composition which
controls microorganisms growth
They are mainly of 2 types
Natural Preservatives
Examples :- Salt , Sugar , lemon juice , spice
Chemical Preservatives
Examples :- Organic and Inorganic foods like Sodium Benzoate ,
Potassium Meta bisulphate , Citric Acid

7. Preservatives
Natural Preservatives
Salt
It returns water through osmosis process in food product thus it
changes composition of food
As a result, no free water is left for microorganisms to grow
Sugar
It absorbs free water from food product thus restricts growth of
microorganisms
Oil and Spices
They form a layer over the food product hence it forms a layer
between air and microorganisms , thus restricting them

8. Preservatives
Acids
Acids
It resists the growth of microorganisms
Examples of acids as preservatives:
Vinegar or Acetic Acid used for preserving onions
Citric acid used for fruit squashes