Agriculture notes prepared by IAS Topper for all agriculture based competitive exams-Horticulture-Preservation of Fruits and Vegetable

Scope For Preservation Of Fruits And Vegetables Preservation

1. Diverse climate and soils

            India has a wise ranging climate. Different types of fruits and vegetables require specific climatic requirements. Therefore varying temperature and moisture conditions provided enough choice for growing different plants. Similarly, more than seven distinct types of soil types also increases the diversity of these crops. India currently ranks second in the world for the total out put of fruits and vegetables.

2. Seasonal nature of production

            Glut in production during a particular season needs elaborate post harvest requirements like processing, transport and distribution, but the poor infrastructure like road and transporting machinery, lack of storage facility result in heavy loss.

3. Perishable nature of the commodity

            Fruits and vegetables contain more moisture with regards to their weight. Therefore they are prone to post harvest damages and pathogen attack. This is the most important limiting factor for heavy post harvest loss. Therefore, food preservation is the only way to prevent further loss.

4. Mishandling and mechanical damage

It is estimated that aour 25 per cent of total production of fruits and vegetables lost due to mishandling and other practices. They can only be reduced through post harvest processing.

5. Social Change

With increasing urbanization, rise in middle class purchasing power and changing food habits, the demand for processed food looks brighter.

Methods of Food Preservation

Fruits and vegetables suffer from enormous post harvest damages due to their perishable nature. Damage during harvest, transport and distribution provide conducive environment for the pathogenic microorganisms thereby causing great loss to the product. In order to reduce the post harvest losses and also to increase the shelf life of the fruits and vegetables, different methods of preservations are used in large scale. Before understanding the different methods employed for preservations, let us now take look at the principles behind the methods.

Principles Of Preservation

Methods of food and vegetable preservation:

Physical Methods

 1. Drying

            Normally the fresh fruits and vegetables contain more moisture to their weight, making them highly prone for pest and disease attack. Therefore, removal of moisture and proper packaging are employed as one of the oldest method for preserving the perishable commodities. At low moisture content, spores and propagules of pathogen fail to germinate, thereby reducing the possibility of damage.

Ex. Dates, Grapes, Onion, Garlic and Potatoes are preserved by this method

2. Heat Treatment

            Applications of heat at controlled level decreases the moisture content of the fruits and vegetables thereby reducing the chances for pathogen attack. Very high temperature coagulates the enzymes and vital proteins of microorganisms resulting in death. Heating the material above 100⁰  Celsius degree normally referred as sterilization, kills the pathogen and stops further contamination. After the heat treatments, the products are stored hermatically.

Ex. Canned fruits and vegetables

3. Freezing treatment

Freezing temperature retard or slow down the growth of micro-organisms. Therefore, the growth of pathogens are arrested and n further damage to fruits and vegetables.

Ex. Fruit Juices are normally stored in fridge.

Preservation by Sugars and Salts

1. Sugars

Sugar content more than 65 per cent retard the growth of mycelium of any fungus. Bacteria and other post harvest pathogens also do not grow at this level of sugar content as it affects the osmotic balance.

Ex. Jams, Jellies, Marmalades, Candies and Crystallized fruits.

2. Salts

Salt concentration above 15 per cent prevents any pathogen to grow in the medium. This is used for the preservation of fruits and vegetables in the form of pickles.

Preservation by chemicals

1. Potassium Metasulphite

When Potassium metasulphite reacts with acids of juices and squashes, it releases sulphur dioxide. Thus the released gas reacts with water and forms sulphuric acid, which prevents the growth of microorganisms. It is found effective against moulds, bacteria and spores of different fungi, however not effective against yeasts. Usually SO2 concentration of 350 ppm is preferred for the preservation.

2. Sodium Benzoate

This chemical is specifically effective against yeasts and other related organisms during post harvest storages. The preferred concentration is 0.06 to 0.1 percent for fruits and vegetables.

 Preservation by Fermentation :

The main product of fermentation is ethyl alcohol, which is detrimental to many of the post harvest pathogens. Therefore, some of the fruits like grapes are preserved in the form of wine for even up to 30 years.

Preservation by other methods:

Vegetable oils, spices like turmeric, pepper and asafetida have been found to have anti bacterial properties. Antibiotics like Nisin, Subtilins and Pimaricin also proved to be good protectants for the post harvest products. Lactic acids, acetic acid (Vinegar) and citric acids have been commercially used in large scale for preservations of fruits. Recently irradiation of the harvested and processed foods has also yielded good results. 

 Types of Gardens

• Kitchen Gardening
• Market Gardening
• Truck Gardening
• Vegetable forcing
• Garden for processing
• Floating vegetable gardening
• Roof gardening