High temperature effects

As well as increasing weight loss and disease, high temperatures can limit the development of colour and ripening in some fruit vegetables. Short periods of high temperatures can benefit long storing root and bulb crops by increasing wound healing. 

Vegetables may be accidentally exposed to high temperatures if left in the sun after harvest or due to a malfunction in the normal cool chain. They may also be heat treated to reduce chilling sensitivity, kill microbes or as a quarantine treatment against insects.

Temperatures over 30°C can destroy the enzymes in vegetables that are responsible for colour changes and maturation. For example, capsicums and tomatoes held at over 30°C may fail to develop normal red colour. High temperatures can stimulate breakdown of chlorophyll, resulting in premature yellowing, and cause rapid softening, wilting and dehydration.

A few vegetables can benefit from exposure to high temperatures during curing. Curing is used to allow the vegetable to heal over injuries inflicted during harvest, such as breaks, cuts or scratches. Products such as sweetpotatoes, pumpkins and onions, may benefit from 7 – 10 days at temperatures between 22 and 30°C, particularly if they have been damaged during harvest and extended storage is planned.