Blast chillers are used for chilling of food. Inside blast chillers, food material is arranged on trays and chilled air has blown by fan resulting rapidly cooling of food. Due to rapid cooling small size ice crystals are formed in food which in turn resulted in better texture of final produce.
Chilling is a unit operation in processing of horticultural crops/ foods where temperature of food is reduced in range of 0oC and 8oC. This lower food temperature retards microbial activity and biochemical changes and helps in extending shelf life of fresh foods.
Chilling can preserve perishable horticultural produce for some days or weeks depending on type of produce. Chilled foods shows no or minimal changes in sensory and nutritional properties.
Freezing on other hand can be accomplished by lowering temperature of food below its freezing point. Freezing of perishable fruits/vegetables can be done by lowering temperature rapidly in blast freezers.
One difference between chilling and freezing is the temperature of refrigeration applied to food. In freezing water in food gets converted into ice and water activity significantly depressed. Frozen foods can be preserved longer than chilled, depending on temperature of storage of frozen foods.
Supply of chilled foods to market needs refrigerated transport and display cabinets with chilling facility. Chilling retards growth of thermophilic microorganisms and many mesophilic microorganisms.
Blast chillers rapidly down the temperature of food. Some fruits/vegetables cannot be chilled as they are susceptible to chilling injury. Different fruits/vegetables has recommended different storage temperature. If temperature goes below than recommended, chilling injury occurs to such fruits/vegetables. Chilling injury reduces quality of fruits/vegetables.
Blast chiller quickly lowers the temperature of food by blowing cold air over the food placed in chiller. The blast freezer allows food to kept at below freezing temperature. Refrigeration methods can used to reduce spoilage of foods but cannot improve initial quality of food, so it is important to select good quality initial food for chilling or freezing.