EFFECTS OF ULTRASONIC TREATMENT ON PERICARP BROWNING OF POSTHARVEST LITCHI FRUIT

Pericarp browning and decline in quality are the major postharvest problems of litchi fruit (Litchi chinensis Sonn.) during storage and transportation. Experiments were conducted to investigate the effects of ultrasonic treatment on pericarp browning and quality of harvested litchi fruit. Fresh fruits of litchi cv. Guiwei were treated with ultrasonic at power of 0 (control) or 120 W for 10 min in water and then stored at room temperature (28C). Application of ultrasonic generally reduced the degradation of litchi anthocyanins and increase in relative leakage rate throughout the storage period, and inhibited the activities of polyphenol oxidase and peroxidase at the early storage stage and, thus, significantly delayed pericarp browning of litchi fruit. However, ultrasonic treatment accelerated the reduction in the amount of total soluble solids and slowed down the increase in total titratable acid. All these results suggest that the application of ultrasonic can effectively control the pericarp browning of postharvest litchi fruit during storage. PRACTICAL APPLICATIONS Litchi fruit has a very short storage life under ambient conditions because of the browning and quality deterioration. Various approaches are now applied to extend the storage life of litchi fruit, such as sulfur fumigation, chitosan coating and acidic treatment. Although sulfur treatment has been adopted widely, sulfur residue remains to be solved. Therefore, a novel postharvest technique ultrasonic sound without hazard to human health is needed urgently. In this study, ultrasonic treatment was used to effectively delay the pericarp browning of harvested litchi fruit. This prospective technique will be helpful to solve the problem of litchi browning from another angle and substitute the chemical approaches of antibrowning to prolong the storage life and control the decay of litchi.