EFFECTS OF PRO-LONG COATING ON CHANGES IN COLOUR AND ENZYME ACTIVITY OF POSTHARVEST LITCHI FRUIT
PRO-LONG涂膜对采后贮藏荔枝果实色泽和酶活性变化的影响

A common litchi cultivar Huaizhi was used to investigate how the application of Pro-long coating affects the browning of litchi peel and relevant enzymes during 4 t storage. The Hunter L and b values in both the control and treated fruits decreased continuously with storage time, indicating that the peel became darker and had less yellow characteristics. The Hunter L and b values in the control decreased faster than those in treated fruits. The Hunter a values ifl both the control and treated fruits were relatively stable during the first 20 days of storage and then significantly decreased during the remaining days, implying that stored litchi fruits maintained basically red characteristics during the first 20 days of storage and then became less red, corresponding to the changes in contents of anthocyanin, flavonoid and total phenolics. Hunter a values in the control decreased faster than those in treated fruits after the 21st day of storage. These correspond to a visible change to a dark red and brown during storage and changes in polyphenol oxidase (PPO) and peroxidase (POD), which indicate that polyphenol oxidase plays a definitive role in postharvest browning, and peroxidase is partially involved in the browning process. The increase in POD activities of treated fruits was slower than that of the control, and the peaks in PPO activities of treated fruits were delayed slightly compared to that of the control. There was no significant difference between 1.5% and 2.5% Pro-long treatments. Therefore, we suggest that the application of Pro-long coating to litchi fruits partially inhibits PPO and POD activities, and influences the breakdown of anthocyanin and the changes in contents of flavonoid and total phenolics, thereby delaying browning progress.