Flowers processing vacuum cooler
What is vacuum cooling? (In detail)
Vacuum cooling removes heat from the vegetables by boiling some of the water in them.
The product is filled in a closed vacuum chamber and the air is pumped out. This reduces the pressure of normal air to a virtual vacuum (<1 kPa). Under these conditions, water boils at <7 ° C.
When the water in the vegetables changes from liquid to gaseous, it absorbs heat energy from the product and cools it down. This steam is removed by being drawn past cooling coils which condense it back to liquid water.
In order for the vegetables to be rapidly cooled in a vacuum, they must be able to easily lose moisture. For this reason, the vacuum cooling is very suitable for leaf products such as lettuce, Asian vegetables and fresh cut flowers. Even products such as broccoli, celery and sweetcorn can be effectively cooled in this way. Vacuum cooling is not suitable for products with waxy skin or low surface / volume rate, eg. Carrots, potatoes, tomatoes or zucchini.
Each time the temperature drops by 5 ° C, about 1% of the product weight needs to be converted to water vapor. Modern water jet vacuum coolers, however, address this problem by spraying water over the product during the vacuum process. This can reduce moisture loss to a negligible level.