Mechanism of quality maintenance during storage in heat-treated horticultural crops

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Heat treatment is a method that horticultural crops are treated with hot air or hot water at 40 to 50℃ for a short time, and the physiological effects on keeping quality have been reported in addition to the control of pathogens and pests by heat treatment We deal with the mechanism of quality maintenance by heat treatment.1) In green sour citrus fruit, Nagato-yuzukichi, we found that the occurrence of chilling injury during storage was suppressed by the heat treatment(hot air treatment at 35℃ for 1 to 3 days) after harvest.2) On the degreening of stored broccoli florets, we determined the characterization of Mg-dechelating substance in chlorophyll degradation and the inhibitory effect of heat treatment (hot air treatment at 50℃ for 2 hours)on degreening.3) We determined that the active oxygens might be involved in the occurrence of chilling injury in cucumber fruit Moreover, the occurrence of the injury was effectively suppressed by the heat treatment (hot air treatment at 45℃ for 2 hours), inferring that the inhibition could be due to the control of the activities of hydrogen peroxide-scavenging enzymes, ascorbate peroxidase and catalase.From these results, we suggest that the heat treatment after harvest has an inhibitory effect on the chilling injury of Nagato-yuzukichi and cucumber fruits and the degreening of broccoli florets. We also imply that the inhibitory effect on chilling injury might be in order to control the changes in membrane lipid and the activities of hydrogen peroxide-scavenging enzymes and that the effect on degreening might be due to the control of the activities of chlorophyll-degrading enzymes, resulting in the quality maintenance of these horticultural produce after harvest.