CONTROLLING POSTHARVEST ANTHRACNOSE OF BANANA USING NOVEL EDIBLE COMPOSITE COATINGS BY STIMULATING DEFENCE-RELATED ENZYMES

Anthracnose is an important postharvest disease on various tropical fruits and vegetables. Chitosan is reported to have antifungal effects against several fungi. In this study the potential of chitosan combined with gum arabic as an edible coating was investigated. Banana fruit were dipped in various concentrations of gum arabic (5, 10, 15 and 20%) incorporated with 1.0% chitosan solutions along with an untreated control and stored at 25°C and 60% RH for 15 days. Disease incidence and the activities of defence-related enzymes were recorded during storage. Compared with untreated control fruit, edible composite coating treatments significantly reduced the disease incidence in fruit inoculated with Colletotrichum musae. The activities of defence-related enzymes such as polyphenol oxidase (PPO), peroxidase (POD), phenylalanine ammonia lyase (PAL) and total phenolics were all significantly enhanced in 10% gum arabic plus 1.0% chitosan treated banana as compared to the control and 5% gum arabic plus 1.0% chitosan treatment. Therefore, it could be suggested that postharvest decay in banana can be minimised by gum arabic plus chitosan composite coating on a commercial scale.