Temperature is an important factor for maintaining postharvest quality of vegetables and greatly influences the rate of deterioration.
Some of the processes associated with deterioration, like respiration, increase with an increase in temperature. For each 10 C increase in temperature, the rate of chemical reactions increases 2-3 times.
Lowering the temperature of vegetables decreases their rate of deterioration, reducing the respiration, extending their shelf-life. There are researchers reported an extension of shelf life of 2.5 days at 12 C for head lettuce, which were cooled for 20 min, sealed in polypropylene film and stored for a week at 2 C.
Precooling involves the rapid removal of field heat after harvest. Vacuum cooling is an ideal way to cool specific fresh produce, such as leafy vegetables and flowers, quickly. A vacuum cooler can cool vegetables down from field temperature to about 2°C in 15 minutes, Keep the best sensory and quality (color, aroma, taste and nutrients) of vegetables, and vacuum cooling also inhibit or kill bacteria and microorganisms.
