Freezing of food is probably the gentlest method of food preservation. Freezing prevents food spoilage by inhibiting micro organic and enzymatic action, and has few adverse effects on taste, texture, nutritive value or color. Most frozen foods are probably the result of an indirect contact freezing process. During this process, the product and a heat transfer fluid are separated by means of an interface or barrier between the cooling medium and the product. This interface can be a metal plate or the products packaging material, which prevents direct contact between the product and the cooling medium. Contact freezing is mainly used to cool packed fish and meat products in blocks with preset linear dimensions.
Typical dosage rates are 45-65 %
Zitrec FC.
Requirements to freezing process
There are quite some requirements to the process of freezing. The time between refrigeration and harvest resp. slaughter must be as short as possible. Also to the refrigerated storage there are many requirements: naturally temperature must be low, but also air circulation and humidity (80 to 95%) must be well controlled.
If conditions have not been optimised, changes of food that can occur during refrigerated storage such as chill injury, flavor or odor absorption, or loss of firmness, color, flavor, and sugar/acid. During refrigeration, there can be concentration effects such as precipitation, salting-out or dehydration. Slow freeze will lead to large ice crystals which is why we want a rapid freeze to -18°C.
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