There are several ways of processing products using cryogenic techniques in the refrigeration industry:
- freezing - lowering the product temperature to - 18 ºC or less;
- cooling - lowering the product temperature to a temperature above freezing;
chilling - lowering the product temperature to a temperature close to freezing.
Freezing and cooling technologies are used to preserve food quality and taste characteristics, to extend shelf life of products.
Products deterioration are caused by bacterium, fermentation and mould. The growth of bacterium is stopped when the temperature is below - 10 ºC, fermentation and mould develop when temperature is above - 18 ºC. During freezing most of the heat contained in the products should be removed as soon as possible. Freezing time depends on the shape, size and thermal conductivity of the product, as well as the heat transfer between the product and refrigerant. Size and location of ice crystals and freezing rate determines the quality of the final frozen product.
Freezing preserves the high quality of production, because product loses a minimal amount of moisture. For comparison: the loss of fluid on the weight of the product during mechanical refrigeration: up to 5%, during cryogenic freezing: between 0,5 and 2%.
Cryogenic freezing and cooling technologies are widely used in meat and fish industry, to freeze fast-food, in bakery and confectionery industry, for freezing ice cream, berries and fruits.
Also, cryogenic technology is used for emergency cooling of warehouses, cooling of ready liquid products, for products pre-freezing before cutting.