Enhanced chilling tolerance in heat-treated mangosteen
Mangosteen is sensitive to low temperature and develops chilling injury (CI) when stored at temperature below 13oC. Postharvest heat treatment has been applied to alleviate CI in various fruits. In this research, induction of CI resistance in mangosteen affected by heat treatment was investigated. Mangosteen was heated with hot air at 35oC for 3, 6, 12 and 24 hours, prior to storage at 7oC. Thereafter, fruit was held for 3 days at 25oC and determined for weight loss, heat injury and CI symptoms. All heat treatments resulted in retarding abnormal ripening. Fruit heated for 3 and 6 hours exhibited smaller extents of browning and shrinkage of calyx and stem after the long-term cold storage, whereas heat treatment for 12 and 24 hours imparted undesirable appearance of calyx and stem, in addition to increased weight loss. The highest extent of pericarp hardening was detected in non-heated and 3-hour-heated fruit after 9-15 days of cold storage. During the cold storage, the lowest electrolyte leakage was found in 6-hour-heated fruit. Heat treatment at 35oC for 6 hours effectively delayed CI occurrence, in terms of abnormal ripening, browning and shrinkage of calyx and stem, hardening of pericarp and electrolyte leakage, with smallest extents of weight loss and heat injury.