Effects of Chinese herbal medicine-starch-chitosan composite coating on fresh-keeping of ponkan

To explore possibilities of using edible film as a substitute for chemical preservation and bagging, effects of fresh-keeping and physiological characteristics of Chinese herbal medicine-starch-chitosan film on citrus fruits (Citrus reticulata cv. ponkan) were investigated. The results showed that composite coating significantly decreased the disease index of citrus fruits and kept a higher percentage of healthy fruit, compared with bagging treatment. However, no difference was found between composite coating and chemical preservation during storage period of citrus fruits. Compared with bagging treatment, the percentage of healthy fruit of composite coating was increased by 20.0% at storage of 90 days, but the disease index was decreased by 50.0%. Composite coating could reduce the loss of vitamin C and titratable acid contents. Composite coating significantly enhanced the activity of catalase and decreased activities of peroxidase and polyphenol oxidase and the accumulation of malondialdehyde. After storage for 90 days, catalase activity of composite coating was 2.2 times as much as that of bagging treatment. Peroxidase and polyphenol oxidase activities and malondialdehyde content were 60.9%, 80.7% and 76.7% of bagging treatment, respectively. Except from peroxidase activity, there was no marked difference on catalase and polyphenol oxidase activities and malondialdehyde content between composite coating and chemical preservation during the storage period. The cost of processing one kilogram of ponkan was 0.16 Yuan. These results suggest that composite coating not only has the same effects on disease resistance and delaying senescence as chemical preservation, but also it gives better fruit quality than chemical preservation. Therefore, composite coating could be used as a substitute for chemical preservation and bagging preservation.