Commercial, the food preservation technique depicts the following processes: 1. Canning and Bottling 2. Machine Drying 3. Freeze drying 4. Cold storage 5. Pasteurization 6. Irradiation 7. Use of antibiotics.
1. Canning and bottling:
Canning involves the process of preserving foods in sealed containers by the application of heat. Primarily, it is based on the principle of sterilization. Firstly, all the micro-organisms present in the food are killed by the applications of heart at 275° to 350°F and then sealed in simultaneously sterilized air tight containers to prevent any further attack of micro organism.
Fruits, vegetables, fruit juices, pickles, cheese, butter, meat, fish etc. are generally canned or bottled.
2. Machine drying:
Dehydration in sunlight is an ancient and the lengthiest process of preserving food practiced at every homes. Understanding the difficulties of this process of preserving food, Scientists have invented different machines to be used for different food stuffs, which are dried at different temperatures. Commercially special type of steam rollers are used for drying milk for reducing it to powder. Similarly, special ovens are sued for drying vegetables at a specific temperature. It is found that this method of preservation is better than those of the traditional method of drying foods in sunlight.
3. Freeze drying:
This method of preserving food is adopted to overcome the difficulties of machine or Sunlight drying. During drying vegetables or fruits by Sunlight or by machine foods are too much squeezed, and do not take the original shape when it is in use. In order to overcome this defect, the process of freeze drying was invented. In this process, food stuffs are kept at a temperature of -20°C for about 12 hours, so that the water content of the food stuffs are converted to ice particles. Then it is dried up by machine under low pressure. When it is to be used, it is dipped in hot water. This method retains the shape of the food stuffs, which is damaged by machines drying process.
4. Cold Storage:
This system has become one of the most popular methods of preserving food-stuffs in rural and urban areas of today. Many seasonal fruits and vegetables are stored in cold storages and according to the demand of the market are carried to the place of requirement. This method is based on the principle of refrigeration. Mostly, vegetables, fruits, eggs, meat, fish are kept in cold storages.
This process is applicable to milk only. In this method milk is boiled at 160°F and then immediately cooled at 55°F. Normally, milk is pasteurised on a large scale to safeguard against any bacterial infection. The process aims at destroying the bacteria and inactivating the rest ones. The pasteurised milk is filled in sterilised bottles which are sealed. It could be preserved for five to six days and the colour and flavor of pasteurised milk does not change in the process, as happens with the boiled milk.
This is a new technique of preservation, which is at the stage of experimentation. The W.H.O. has advised the use of this process only in the case of wheat, onions and potatoes. In this process, gamma rays or high speed electrons are used to destroy micro-organism. These radiations are termed as ionising radiations. The best advantage of this process is that the food can be stored without refrigeration.
7. Use of antibiotics:
This is another method of preservation now under study. Use of antibiotics in food stuffs have considerably, increased during these days. When fish and poultry are treated with antibiotics, their self life increases two to three times because of the reduced growth of the micro-organisms. Similarly antibiotics are used in the ice crush, which is used for packing raw fish and shell fish.’