Preharvest sprayable 1-methylcyclopropene (1-MCP) effects on fruit quality attributes and cell wall metabolism in cold stored ‘Fuji’ apples

This study was carried out to investigate the effects of a pre-harvest treatment with sprayable 1-methylcyclopropene (S1-MCP) on fruit quality and cell wall metabolism during cold storage of ‘Fuji’ apples (Malus domestica Borkh). Three different treatments, 95, 125, and 250 mg·L^-1 S1-MCP, applied at 1, 2, or 3 weeks before harvest, were used in this study. Fruit firmness of untreated fruit decreased from 62.3 Newton (N) at harvest to 55.3 N at 180 days after storage. However, a treatment with 250 mg·L^-1 S1-MCP at 2 or 3 weeks before harvest maintained a high flesh firmness of 60 N even after 180 days of cold storage. The titratable acidity (TA) of untreated fruit decreased rapidly from 0.36% at harvest to 0.19% at 180 days after storage, but the 125 and 250 mg·L^-1 S1-MCP treatment at 2 weeks before storage maintained the TA at 0.32-0.33% after 180 days of cold storage. The internal ethylene concentration was significantly increased to 326.4 µL·L^-1 after 180 days of storage in untreated fruit, but it remained very low (17.3 and 32.4 µL·L^-1) after storage when fruit were treated with 250 mg·L^-1 S1-MCP at 2 and 3 weeks before harvest, respectively. The uronic acid content, which is a component of the cell wall middle lamella, in alcohol insoluble material (AIS) was higher (301.47 µg·mg^-1·AIS^-1) in the S1-MCP treated fruit after 180 days of storage compared to the untreated fruit (271.72 µg·mg^-1·AIS^-1). The activities of α-and β-galactosidase in cell wall hydrolases were significantly lower in S1-MCP treated fruit than in the untreated fruit after 180 days of storage.