The Principles of Freezing Seafood
Freezing of fish takes place in three stages. The first stage involves the removal of heat and the lowering of temperature of the product to the freezing point.
The third stage involves the subcooling of the food from freezing point to its terminal temperature.
The process of freezing is actually the transfer of heat from one material to another. The heat transfer is affected by the different factors such as:
*The difference in temperature between the fish and the cooling medium
*The method of heat transfer
*The type and technique of packing
*The thermal properties of the fish to be frozen.
In freezing , the transfer of heat, is primarily achieved by conduction or convection. The movement of heat from one center section of the product to its outer surface is a function of temperature difference and product thickness.
In the process, the heat from the center moves to the surface then to the cooling medium be it brine, air or refrigerant circulating in contact plates by forced convection of radiation.
The transfer of heat to the cooling medium varies with the velocity of the gas or liquid, its thermal properties, and its temperature.
The time required for freezing is influenced by different factors, such as thickness of the product type of package and method of packaging.
Packaging materials having low conductivity slow down the removal of heat from the product. A suitable material for packaging should have high thermal conductivity, which should be thin enough to allow rapid transfer of heat from the surface of the product to the cooling medium.
The fit of the package will also affect the freezing time and low freezing efficiency.
The Principles of Freezing Seafood
