Freezing by Contact with a Cooled Gas

Different methods are available for freezing by contact with cooled gas. These include:

i) Cabinet Freezing: This method involves circulation of cold air in a cabinet where the product is placed in a tray. The moisture pick-up from the product may deposit on the cooling coils as frost, which acts as an insulation.

ii) Air–Blast Freezing:  The method employs the use of high  velocity cold air to reduce the temperature of the food.  Air velocities between 2.5 and 5 m/s give the most economical freezing. Lower air velocities result in slow product freezing and higher velocities increase unit freezing costs considerable. This method can be further divided into fluidized bed freezing, belt freezing, and tunnel freezing, depending on how the air interacts with the product.fruits. The high degree of fluidization improves the heat transfer rate and results in good use of floor space.