Virtual Open Schooling Online courses available at Virtual Open Schooling (VOS), for more details kindly click here!
NIOS Silver Jubilee Year

Preservation Methods

Jump to: navigation, search

Mindmap.pngConcept Map


This OER enables you to:

  • define food preservation
  • make use of one the simple methods of food preservation
  • explain the importance of food handling


Shilpa: -Suppose I want to eat a mango in winter seasons? Is it possible?
Mamma: - Why not, it is possible.
Shilpa: - How is it possible?
Mamma: - You know that mango cold drinks available in all seasons .Some food items like mango pickle are also available trough out the year.
Shilpa: - Why don’t they spoil?
Mamma: - Do you know how food is preserved?
Shilpa: - I don’t know about it .Please tell me.

Food preservation

A process by which certain food likes food and vegetables are prevented from getting spoilt for a long period of time. The colour, test, and nutritive values of food is also preserved. Foods have to be prevented from getting spoilt. We have to ensure that there should not be any change in color or taste . We also have to ensure that there is nochange in nutritive values

Why we should preserve foods?

  • If we are able to preserve foods, we can use different foods off season .e.g mango is preserved and used as mango juice, mango pulp, pickle, raw mango powder etc.
  • We eat food even it is not available in our areas! For example: - American foods are also available in India in some other form!
  • Preserved food is easy for storage
  • Preserved food items are easy to transport from one place to another.


Fill in the blanks 1) In food preservation ………value is also preserved.

2) Food …………avoided by preservation of food.

Why does food get spoilt?

See the OER on Food Food Spoilage

Methods of Food Preseravtion

Following are the methods used for food preservation.

Application of heat:

• Heat inactivates enzymes.
• Kills microorganisms- most bacteria are killed in the range 82-93o C

Thermal processing (Heating):-

Thermal processing can be done by following methods:

• Blanching- The process of dipping the vegetables in boiling water for a specific period. E.g. Carrot, Cabbage etc.
• Pasteurization- In this method food is heated at very high temperature and then quickly cooled. e.g. Milk, for example

Removal of heat (cold processing):

Application of cold processing Low temperature decreases the rate of enzymatic, chemical and microbial reactions in food so it slowdowns microbial growth. The storage life of food is extended. Cold processing can be done by following ways.

• Refrigeration- Food stored in low temperature, about 50C. E.g. Milk and milk products
• Freezing- Food store at 00C e.g. Ice creams

Control of water content (drying):-

Microorganisms require free water for activity. After removing free water from the food microbial cells multiplication will stop because water is unavailable for biochemical reactions. Hence shelf life of life food gets extended.

Control of water in food can be done by following ways:-

• Physical removal of water from food (dehydration)
• Removal of some of the water from food (concentration)
• Addition of substances that bind water in food, making it unavailable (sugar, salts)

Radiation (Use of microwave):-


• Ionizing radiation inactivates microorganisms in food.
• Treatment with microwave inactivates enzymes in food
• Ultraviolet ray are used to sterilize air and water used in food processing

Removal of oxygen from food inhibits oxygen dependant enzymatic and chemical reactions which inhibits growth of aerobic microorganisms.

This can be done by following ways:-

• Paraffin wax- coated on cheese cube
• Nitrogen back flushed bags - Oxygen replace by nitrogen in the packs. E.g. Potato chips
• Canning food (cured meats)

Addition of chemicals (Preservatives):-

Additives in the food increase the shelf life of food by controlling the growth of the microorganisms. Preservatives are of 2 classes

1) Natural Preservative- Salt, sugar, lemon juice, spice;
2) Chemical preservatives- Organic and inorganic acids

Here are some preservatives used for the food preservation:-

1) Salt: How salt work as a preservative? Salt in food changes composition of the food and osmosis starts in the food. Which result in water comes out of the food. And when there is less water less growth of the microorganisms. Salt is used in pickle, Chatni, sauce etc. 2) Sugar: How Sugar prevent food spoilage? Sugar dissolves in the water available in the food and results in less water available for the growth of the organisms. 3) Oils and Spices: This preservative helps to avoid contact of the microorganisms with the food and prevent contact of air with the food, hence no spoilage of the food. E.g. In pickle oil and spices are used in large quantity. 4) Acids: Lemon juice, vinegar, citric acid etc are used as preservatives. Vinegar is used to preserve onion, tomato ketchup, lemon juice for pickle, citric acid in squashes etc


Points added for a correct answer:  
Points for a wrong answer:
Ignore the questions' coefficients:

1. Addition of the spices in the food allows microorganisms grow quickly.


2. Sterilization increases the activity of the microorganisms.


3. In making of the squashes, we make use of any acid for the preservation.


Your score is 0 / 0


In this lesson we have learned what is food preservation , different ways of preservation used for increasing shelf life of the food.

Inkpot.png Assignments

Find out traditional way of the food preservation in your home. Enlist the 5 ways of preservation with the examples.