Quality maintaining of 'Daw' longan using chitosan coating.

摘要

Postharvest loss of longan (Dimocarpus longan) is associated with pericarp browning and hardening, and disease decay. Chitosan, as an edible coating containing a positive ionic charge, has been reported to inhibit the growth of some microorganisms and to reduce browning disorder in some fruits. Longan cv. Daw fruits were coated with 0, 0.5, 1.0 and 1.5% (w/v) chitosan (low molecular weight) and stored at 4 degrees C and 90-95% RH after air-drying. Chitosan treatments slightly reduced weight loss of stored longans in relation to a reduction of pericarp hardening. Polyphenol oxidase [catechol oxidase] (PPO) activities monitored in the pericarp dramatically increased during storage (20 days). Although chitosan at all concentrations reduced increasing activities of PPO, chitosan slightly reduced the pericarp browning. L values (Hunter scale) of longan pericarp declined gradually in relation to an increase of browning throughout the storage period. Chitosan coating at 1.0 and 1.5% effectively retarded disease growth on stored longans with less than 4% disease incidence at day 20. Longans coated with chitosan exhibited less respiration and maintained amounts of ascorbic acid in aril pulp. Fruits coated with chitosan at 1.0 and 1.5% had a storage life of 16 days..