Vacuum cooling is one of the fastest and most effective ways to pre-cool vegetables, flowers, and other fresh products. Water absorbs heat as it evaporates inside a low-pressure environment. The product is placed in an airtight chamber, where high-capacity vacuum pumps reduce pressure to approximately 4.6 mmHg.

As long as chamber pressure remains low, evaporation continues. Holding the system near 4.6 mmHg long enough can bring product temperature down to 0°C (32°F) in approximately 20–30 minutes. Even microperforated packaged products can be cooled using this process.