Changes in fruit quality attributes, cell wall materials, and related hydrolases activities in 1-methylcyclopropene (1-mcp)-treated ‘honggeum’ apples during cold storage

We investigated the effects of 1-methylcyclopropene (1-MCP, SmartFresh™) concentrations on fruit quality attributes associated with softening and cell wall metabolism in ‘Honggeum’ apples. Fruits were treated with 0, 0.5, or 1 µL·L^-1 1-MCP and stored at 0 ± 1°C for up to 6 months. In comparison with the untreated fruits, both 1-MCP concentrations similarly reduced the internal ethylene concentration and delayed the reduction in firmness and titratable acidity; however, weight loss and soluble solids content were less affected by 0.5 µL·L^-1 1-MCP compared with 1 µL·L^-1 1-MCP. Peel color variables (L* and b*) were not changed by either 1-MCP treatment on both the sunlit and shaded sides. Only the a* value on the shaded side was slightly decreased among untreated fruits at 3 and 4 months in comparison with 0.5 µL·L^-1 1-MCP-treated fruits. The uronic acid and total sugar contents of the cell wall and cell wall hydrolase of the enzyme activities (αgalactosidase, β-galactosidase, β-glucosidase, β-arabinosidase, β-xylosidase, and α-mannosidase) were much greater in fruits treated with 1 µL·L^-1 1-MCP than in fruits treated with 0.5 µL·L^-1 1-MCP and in untreated fruits. Overall, the results suggested that 1 µL·L^-1 1-MCP may be an effective concentration to retain fruit quality attributes and delay fruit softening in ‘Honggeum’ apples during cold storage by reducing enzymatic activities related to cell wall hydrolysis.