Vacuum precooling means that under normal atmospheric pressure (101。325kPa), water evaporates at 100 degrees C。 If atmospheric pressure is 610Pa, water evaporates at 0 C, and the boiling point of water decreases with the decrease of ambient atmospheric pressure。 Boiling is rapid evaporation, which absorbs heat rapidly。 Fresh fruits and vegetables are placed in a closed container, and the air and steam are extracted quickly。 As the pressure continues to decrease, the fruits and vegetables will be cooled by the constant and rapid evaporation of water。
Compared with other cooling methods, the vacuum cooling method has the following characteristics:
It can be transported directly without cold storage, and short distance transportation can be done without thermal insulation vehicles。
The cooling time is very fast. It usually takes only 20 minutes.
The best sensory and quality (color, aroma, taste and Nutrition) of fruits and vegetables are maintained.
It can inhibit or kill bacteria and microbes.
It has "thin layer drying effect" - some minor injuries on fruits and vegetables can be healed or will not continue to expand.
There is no pollution to the environment.
The operation cost is low.
It can extend shelf life, and vacuum precooling leaf vegetables can directly enter high-grade supermarkets without refrigeration。
It can also be used for pre cooling fresh edible mushrooms, fresh cut flowers, raw and fresh meat, rice, steamed products, cooked food, etc。 It is especially suitable for cooling goods to extend shelf life。