Air blast and immersion freezing

A complete description of air blast and immersion freezing.

1. Air Blast Immersion Submitted to – Milli Dey Submitted By- Anuharsh Gaur (15-IFT-011)

2. Freezing It is a unit operation . Temperature of food product is generally below -18 °C or below. Change in state. Allows preservation of taste, texture and nutritional values in food. Extended shelf life. Retards growth of microorganisms.

3. Principles of freezing Lower temperature inhibits growth of microorganisms and limit enzyme activity. Formation of ice crystals draws available water from foods preventing growth of microorganisms.

4. Types of freezing

5. Air Blast Immersion ??????

6. Types of freezer Blowing a continuous stream of cold air over the food products - air blast freezers. Immersion in or spraying with a refrigerated liquid - immersion or spray freezers.

7. Air blast freezer Working mechanism:  These freezers generally have a conveyer belt which is made up of perforated stainless steel. This belt carries food to be frozen. There are electric fans mounted over the conveyer circulating chilled air through the perforations over the products.

8. Cont.. Forced air is used. A blast freezer can chill food from cooking temperatures which is around to +70 o C to -18 o C within 240 minutes. As the temperature in this freezer drops quickly, they can freeze food with smaller ice crystals thus causing lesser damage. Air is recirculated over food at between 30ºC and 40ºC at a velocity of 1.5–6.0 m/s.

9. cont.. The advantage of the blast freezer is its versatility. It can cope with a variety of irregularly shaped products and whenever there is a wide range of shapes and sizes to be frozen, the blast freezer is the best choice. It   is ideal for storing larger batches of leftovers. Thus it reduces food wastage and increase chef’s menu options for future use.

10. cont Continuous air blast freezer- In this type of air blast freezer, the food products are conveyed through the freezer (on trucks or trolleys or they may be loaded on a continuously moving belt or conveyor) usually entering at one end and leaving at the other. Batch air blast freezer - The freezer is fully loaded, and when freezing is complete, the freezer is emptied and reloaded for a further batch freeze. Apart from this difference in mode of operation, the batch freezer gives rise to bigger fluctuations in the refrigeration load than continuous or batch-continuous freezers.

11. Immersion freezing Traditionally foods were immersed in solution of salt and ice for hours , however this process is rarely used liquid refrigerant is sprayed directly on food product. The food products are kept in liquid refrigerant (glycerol, sugar and salt solution) with time varying from seconds to 1 minute depending on size and requirement of food product. Efficient heat transfer.

12. Cont.. Refrigerant may enter the food products causing adverse changes in its quality. Usually done with shrimps and fishes.

13. Conclusion It does not matter what type of freezer we are using for refrigeration the main principle should be focused on fast freezing. Cost of operation, available capital should be focused. Size of food product is important factor.

14. References http://www.fao.org http://www.epack.in http://cshprotocols.cshlp.org

15. Thank you