Food preservation

Food preservation-various methods

                   Centuries ago people knew that if food was not stored or handled properly, the food would go "bad" and this could lead to sickness. Consequently, they learnt how to preserve food using salting, drying, pickling, smoking and freezing methods to stop it deteriorating through the action of bacteria, yeast and moulds. Some appropriate methods and techniques of preservations can considerably reduce wastage of perishable food materials. Food preservation, in fact, offers several advantages:

1. Augmenting food supply, especially out of seasons. 

2. Reducing food wastage making up for dietary inadequacies increasing the storage period of food stuff and ensuring their availability in distant places.

        Food preservation essentially means longer retention of the nutritive value of perishable food materials.

Methods of food preservation

The different methods of food preservation are

1. drying and dehydration

2. canning

3. refrigeration

4. addition of food preservatives 

5. pasteurization.

Drying and dehydration: Drying and dehydration remove water from food. The micro organisms are therefore unable to grow without water. Thus spoilage of food is prevented to some extent. Vegetables, fruits, meat and fish are dried by spreading them out in the sun. Thus these can be stored.

Canning: By cooking, we kill the micro organism but cooked foods cannot be kept fresh for a longer time. Canning is the method by which food can be preserved for a long time. In canning the food stuffs are exposed to high temperatures to kill the harmful micro organisms and to inactivate the enzymes. These foodstuffs are then sealed immediately in the air tight containers. Canned food can be preserved in a good condition for many months.

Refrigeration: Refrigeration is the method by which food is preserved at low temperature. By this method preserved foods are kept as fresh as possible without much loss of vital food values.

Addition of food preservatives: Salt, sugar, honey and oil are good preservatives. Salt and oil are used for preserving meat, fish, vegetables and pickles. Sugar and citric acid are added as preservatives in the preparations of jam and jellies.  

Pasteurization: Pasteurization is a process by which the disease causing bacteria in the milk are destroyed without losing its nutritive values. The milk is boiled at 60°C for thirty minutes and cooled quickly. This is the contribution of Louis Pasteur.

              Whatever the method is used for preservation of food, cleanliness and general sanitary conditions are important. Every effort should be taken to avoid contamination of food by dust, dirty utensils, soiled work surface and hands.