4. Discussion
Coating fruits with semi-permeable films has been shown to retard ripening by modifying the endogenous CO2 and O2 and to cease lower respiration rates (Banks, 1984, El Ghaouth et al., 1991 and Lowings and Cutts, 1982). In our studies, the application of chitosan coating delayed the change in eating quality, reduced respiration rate and weight loss, and partially inhibited the increase of PPO activity of longan fruit which is associated with peel discoloration. This implies that the chitosan coating may form a protective barrier on the surface of the fruit and reduce the supply of oxygen.