Vacuum cooler & Hydro-vacuum cooler brief introduce
Vacuum cooling means that the pressure in an airtight chamber is lowered. Water in the vegetables becomes vapor and absorbs heat energy. Vacuum cooling works best for products that easily lose water, such as lettuce and baby leaf crops.
Hydro-vacuum coolers add a misting system to prevent moisture loss of the product. At the same time, water cooling can cool faster and make some compact vegetables suitable for vacuum cooling.
Vacuum cooling is a fast and energy-efficient method of keeping food.
What is vacuum cooling? (In detail)
Vacuum cooling removes heat from vegetables by boiling off some of the water they contain.
The products are loaded into a sealed, strong vacuum chamber and the air is pumped out. This reduces the pressure of normal air to a virtual vacuum (<1KPa). Under these conditions, water boils at <7 ° C.
As the water in the vegetables changes from liquid to gas, it absorbs heat energy from the product and cools. This vapor is removed by pulling it past cooling coils, so that it is condensed again in liquid water.
For vacuum cooling to cool vegetables quickly, they must be able to easily lose moisture. That is why vacuum cooling is extremely suitable for leaf-like products such as lettuce, Asian vegetables and freshly cut flowers. Products such as broccoli, celery and sweetcorn can also be effectively cooled with this method. Vacuum cooling is not suitable for products with waxy skins or a low surface / volume rate, e.g. carrots, potatoes, tomatoes or zucchini.
For every 5 ° C reduction in temperature, approximately 1% of the product weight must be converted to water vapor. However, modern hydro-vacuum coolers address this problem by spraying water over the products during the vacuum process. This can reduce moisture loss to negligible levels.