Vacuum cooling is a rapid type of pre-cooling, which also helps preserve vegetables by
putting them in an almost complete vacuum. The field heat and heat from the vegetables'
biological processes are used as water changes to vapor and the vegetables become
increasingly cooler. Vacuum cooling helps keep vegetables in good marketable condition while
in storage. The most rapid deterioration in quality of produce occurs soon after harvest, so
the quicker the produce is vacuum cooled, the longer it will retain its initial quality.
Produce can be vacuum cooled just as readily when packaged. The container does not effect
the vacuum cooling, as long as the container is not completely sealed. Most lettuce is now
vacuum cooled, and almost any vegetable can be vacuum cooled.