Effects of Intermittent Warming and Heat Treatment on Postharvest Physiology of Plum Fruits

Plum(cv.Purple) fruits were treated with intermittent warming and heat treatment after harvest,with their brown degree,antioxidant enzyme activities,antioxidant content,membrane peroxidation level,total phenols and titratable acid contents were investigated.The results showed that intermittent warming and heat treatment could properly restore antioxidant activity depressed by chilling injury,eliminate active oxygen free radical,reduce the accumulation of membrane peroxidation production MDA,inhibit the activities of PPO and POD,strengthen resistant system to low temperature and prevent polyphenol metabolism by adversity,thus deferred and lightened chilling injury and browning symptom.At the same time,both treatments also inhibited titratable acid content decreasing and SSC/TA increasing,postponed mature and senescence.Plum fruits could be stored in intermittent warming condition for 60 days without other treatments.We preliminarily considered that this change-temperature treatment pattern which temperature raised to 18～20℃ for 24 hours every 15 days during cold storage at-0.5～0℃ was the optimal storage condition for 'Purple' plum.