Effects Of Oxalic Acid And 1-Methylcyclopropene Treatments On The Chilling Injury Of 'Youhou' Sweet Persimmon During Cold Storage

Sweet persimmon softens rapidly during storage at room temperature.While low temperature can slow ripening,fruit are sensitive to chilling injury?CI?at low storage temperatures.Oxalic acid?OA?is a metabolite of living organism.It is found that exogenous of OA treatment can delay senility and inhibit CI of postharvest fruits.1-methylcyclopropylene?1-MCP?,as an inhibitor of ethylene receptor,has been widely used in maintaining fresh of fruits after harvest.At present,the effect of OA treatment in sweet persimmon on CI has not been reported at home and abroad.In this study,we investigated the effects of different concentrations of OA treatments on the CI of‘Youhou'sweet persimmon during cold storage,and it showed the best concentration of OA.We also investigated the effects of OA,1-MCP,and combined OA and 1-MCP treatments on the CI of‘Youhou'fruit during cold storage at 1±0.5?,RH 90%±5%.The results are as follows:1.5 mmol·L^-1,15 mmol·L^-1,25 mmol·L^-1 OA treatments significantly inhibited the increase of respiratory rate and firmness,reduced CI incidences and CI indices,and alleviated CI symptoms in‘Youhou'fruit.5 mmol·L^-11 OA treatment showed the best results.2.CI symptoms identifiable as browning of the flesh and surface in‘Youhou'fruit.The browning of the pulp spread in a transverse pattern from the skin to the core,and profiles showed a gradual spread beginning at the calyx end of the fruit and extending to the stem end.OA,1-MCP,and OA+1-MCP treatments inhibited the development of CI symptoms,reduced CI incidences and CI indices.The combined treatment of OA and 1-MCP was more effective than either one alone resulting in the lowest CI in‘Youhou'fruit.3.OA,1-MCP,and OA+1-MCP treatments maintained higher levels of L*,soluble solid,soluble tannin contents and firmness,inhibited the increase of respiratory rate and ethylene production,and reduced weight loss rate and rot rate after the end of storage in‘Youhou'fruit.The results indicated that OA,1-MCP and OA+1-MCP treatments alleviated the quality loss and delayed senility of‘Youhou'fruit during cold storage.OA+1-MCP treatment showed an optimal result.4.Chilling-induced membrane damage was inhibited by all treatments as indicated by lower electrolyte leakage and malondialdehyde concentrations than found in control fruit.The treatments suppressed phenolics oxidation associated with polyphenol oxidase and peroxidase activities,resulting in lower skin and flesh browning.OA,1-MCP and OA+1-MCP treatments decreased lipoxygenase activity,promoted superoxide dismutase and catalase activities.These results suggested that all treatments reduced the membrane damage of‘Youhou'fruit during cold storage.The treatments enhanced pectin solubilization and maintained higher polygalacturonase activity and juice yield compared with the control.The combined treatment of OA and 1-MCP was more effective than either one alone.To sum up,OA treatment has obvious effect on reducing the CI of‘Youhou'fruit,and the OA+1-MCP treatment has more superposition effect.