Fast freezing

Fast freezing, also called "deep freezing" is a low temperature preservation technique that is carried out in a very short time, bringing the temperature of the product in all its points to values equal to or lower than -18 ° C and keeping it continuously, while freezing occurs in longer times. The freezing process is regulated by law no. 110 of 27 January 1992. Rapid freezing is used to cool various types of products (vegetables, fruit, fish, meats, etc.) in a pre-established time, to safeguard their properties and the hygienic safety of food. The freezing time depends on the thermal conductivity of the product, on the difference in temperature between the product and the coolant and on the time that the product remains in contact with the coolant.

TYPES OF FREEZERS CONTINUOUS FREEZERS Continuous freezers are suitable for small and large quantities of product and are made with a tunnel shape that can be ribbon, net or spiral. The product is loaded onto the conveyor which moves inside a thermally insulated tunnel and cooled by a stream of air at a temperature of around -35 ° C and comes out frozen from the opposite end. The air is cooled by an evaporator and put into circulation by fans installed inside the tunnel. FLUID BED FREEZERS The fluidized bed freezers are continuous functioning and are suitable for small size products. The product moves into a channel with the perforated sheet bottom under which air is blown at a temperature of -35 ° C. The air causes the product to move from the inlet to the outlet, keeping it in suspension and at the same time the freezing process takes place. PLATE FREEZERS The plate freezers are discontinuously operated. Loading and unloading of the product can be manual or automated. The product is loaded between double-walled plates inside which the refrigerant fluid circulates at approximately -40 ° C. The plates are brought closer so that two sides of the product are in contact with the plates. The heat is transmitted by conduction from the product to the fluid. There are models with horizontal plates used for packaged or solid-state products and vertical plates for loose products. For small productions, halogenated fluids (Freon,) are used as refrigerant, while for medium and large productions ammonia. The evaporation temperature of the refrigerant fluid is normally -35 ° C / -40 ° C. These evaporation temperatures require a special refrigeration system normally built with two-stage compressors (compound) or with low pressure compressors (boosters) or with screw compressors with economizer.