Applications of freezing for food preservation

freezing technology is used for food preservation and to maintain food quality. An effective freezing system can reduce the processing cost and make it affordable to be adopted by the normal processor or consumer. 

What is the Need for refrigeration for food ?

1. To preserve the food as it is received i.e. maintain the food quality as it is kept inside the refrigerator.

2. To extend the shelf life of the food product in comparison to ambient storage.

3. The most important point to keep in mind is that refrigeration does not improve the quality of the food product.

What is shelf life ? 

It is the time in which a food material remains in desirable color, texture, flavor, and nutritional properties and fit for consumption.

What is preservation..?

Mechanism of Food Preservation  by Refrigeration technology

Types of food 

A) Non-perishable foods:

I) These foods do not require refrigeration.

ii)They can safely stored at room temperature in packaged form.

iii)They have very low water activity.

iv) These foods have a much longer shelf life.

v) The rate of decay or deterioration is too slow.

For example., Low moisture food products like dry/dehydrated food products, canned foods etc.

B. Semi-perishable foods

I) These are also stored at room temperature and generally do not require refrigeration.

ii) But has a limited shelf life.

For example: Potato, pumpkin, onion etc. 

C. Perishable Foods

1. These foods are highly prone to spoilage.
2. As they have a greater range of water activity.
3. They require refrigeration to increase their shelf life.
4. Due to greater degree of aw, these foods are highly prone to yeast and mold infection particularly fruits.
5. High sugar content+low pH+higher aw-highly prone towards Yeast and mold contamination
6. For example., Fruits, vegetables, milk and milk products, fresh meat, fish etc.

Refrigeration of perishable foods

• It is well-known that some bacteria are responsible for the degradation of food, and enzymatic processing causes the ripening of perishable foods.
• The growth of bacteria and the rate of enzymatic processes are reduced at low temperatures.
• This helps in reducing the spoilage and improving the shelf life of the food.
• It can be seen that the storage temperature affects the useful storage life

     significantly.

In general the storage life of most of the food products depends upon water  activity, which essentially depends upon the presence of water in liquid form in the food product and its temperature.

Hence, it is possible to preserve various food products for much longer periods under frozen conditions.

Temperature vs Shelf life

Refrigeration of fruits and vegetables

1. In case of fruits and vegetables, the use of refrigeration starts right after harvesting to remove the post-harvest heat, transport in refrigerated transport to the cold storage or the processing plant.
2. A part of it may be stored in cold storage to maintain its sensory qualities and a part may be distributed to retail shops, where again refrigeration is used for short time storage.
3. Depending upon the size, the required capacity of refrigeration plants for cold storages can be very high.
4. Ammonia is one of the common refrigerants used in cold storages.

Typical cold storage

1. The cold chain has proved to be very effective in reducing spoilage of food and in food preservation.
2. It is estimated that in India, the post-harvest loss due to inadequate cold storage facilities is as high as 30 percent of the total output.
3. The quality of the remaining 70 percent is also affected by inadequate cold chain facilities.
4. This shows the importance of proper refrigeration facilities given the growing food needs of the ever-growing population.
5. Refrigeration helps in retaining the sensory, nutritional, and eating qualities of the food.
6. The excess crop of fruits and vegetables can be stored for use during peak demands and off-season; and transported to remote locations by refrigerated transport.
7. In India, the storage of potatoes and apples on a large scale and some other fruits and vegetables on a small scale, and frozen storage of peas, beans, cabbage, carrots, etc. has improved the standard of living.

Recommended storage conditions for fruits and vegetables