Food preservation are classified as physical methods and chemical methods.
Physical method of food preservation include removal of micro-organism by the use of high temperature, low temperature, drying and irradiation methods
The different physical methods of food preservation are
- By removal of heat (use of low temperature) : Removal of heat (freezing) from the food material destroy or slow down the growth of micro-organism. Moreover at low temperature the chemical decomposition of food and enzymatic activities are also less. Therefore, it is very much essential to store food at lower temperature. This method is commonly used for preservation of milk, fruit, meat and vegetables.
- By adding of heat (use of high temperature) : One of the oldest method of food preservation is drying the food by heating. Heating reduces the quantity of water in food and prevents the long term microbial growth. This method is commonly used for preservation of cereal grains such as wheat, jowar, maize, rice and different pulses. The early method of drying was by direct exposure of food to the sun rays, while in modern method, it is carried out in ovens.
- By removal of water : Majority of food stuffs contain excess of water. Dehydration is the process by which surplus water is removed without, changing the taste and nutritive value of the food. The principal of dehydration is that bacteria are unable to survive in the absence of moisture. Sun drying is the most common method of dehydration. Other methods such as cabinet drying and oven drying are also used.
- By Irradiation : In this method food is bombarded by high energy radiations like gamma rays or fast moving electrons, by which bacteria, fungi and insects are killed. The major benefit of irradiation is that it can be used even after food is packages and sealed.This method is used in preservation of milk and fruits.
Published in: Cooking