Vacuum Coolers essentially create a vacuum in a sealed chamber with the produce, usually leafy vegetables such as lettuce, where a great deal of the surface area of the tissues are exposed to the vacuum.
As the pressure falls, water in the tissues literally begin to boil and turn to vapor. This energy is known as the Heat of Vaporization. The change of state must pull heat from somewhere, so it pulls it from the plant tissue – rapidly, depending on the vapor-pressure.
This is fine for rapid cooling, but it also is stressful to the plant tissues and excess water can be driven off by the process – resulting in a loss of sellable weight.
Vacuum cooling can be applied shortly after harvesting crops, helping to rapidly cool the product and preserve shelf life. The theory of the process is to reduce product temperature from ambient temperature, say 90°F (32°C) during the harvest season, to around 39°F (4°C)—within 30 minutes. The process can be applied to vegetables, fruits, flowers and other food products. It is an excellent way to preserve and extend freshness, and can also ensure product uniformity. By using vacuum cooling, in conjunction with other vital pieces of the cold chain, product freshness can be better sustained.
More cooler details please refer to: https://www.iceups.com/vacuum-cooler/