Effects of 1-methylcyclopropene (1-MCP) on ripening of apple fruit without cold storage

The objectives of this study were to determine the efficacy of 1-methylcyclopropene (1-MCP) treatment on ripening of 'Tsugaru' fruit at different stages of maturity (early, mid-, and late harvest) and the responses of the early- to late-maturing apple cultivars, 'Tsugaru', 'Hongro' and 'Fuji', respectively, during storage at ambient temperature (20 degrees +/- 2 degrees C). Fruit at different stages of ripening were treated with 0.5, 1.0, or 2.0 mu l l(-1) 1-MCP for different durations (e.g., 1.0 mu l l(-1) 1-MCP for 8 h, 16 h, or 24 h) or with various delays before treatment (e.g., 1.0 mu l l(-1) 1-MCP on the day of harvest, or 1 d, or 2 d later). Application of 1-MCP to unripe fruit inhibited ethylene production, lowered the rate of respiration and maintained titratable acidity (TA) more effectively than when more mature fruit was treated. However, the effects of 1-MCP on flesh firmness were similar for apples at mid- or late harvests. 1-MCP treatment of early-harvested fruit of the early-maturing 'Tsugaru', which had the highest level of ethylene production and respiration rate, inhibited softening and loss of TA to a greater extent than for late harvested fruit. The same pattern of softening was found for 'Hongro' and 'Fuji'. Firmness of 'Tsugaru' and 'Fuji' apples was maintained after 8 h treatment with 1.0 mu l l(-1) 1-MCP. while a 16 h treatment was required for 'Hongro'. Treatment delays of <= 2 d before the application of 1-MCP had no negative impact on fruit firmness. Overall, these results indicate that 1-MCP can be used to maintain the quality of non-refrigerated apples.