Efficacy of Sprayable 1-MCP on Apple Quality at Harvest and after Storage: The Ontario Experience

Abstract

A sprayable formulation of 250 μL·L-1 1-MCP and 1% oil adjuvant was applied to mature `McIntosh', `Empire', and `Delicious' apple trees 1 week prior to anticipated optimum harvest. Other spray treatments included: none, 1% oil adjuvant alone, and a formulation of 125 μL·L-1 1-MCP and adjuvant (`Empire' only). Unsprayed fruit were treated postharvest with or without gaseous 1-MCP (1 μL·L-1). At harvest, internal ethylene concentration (IEC), starch index, firmness, and soluble solids concentration were measured, as well as CO2, ethylene, and total volatile production of fruit samples over a 14-day period at 22 °C. Additional fruit samples for all preharvest and postharvest 1-MCP treatments were held 14 days at 22 °C and IEC and firmness measured for treatment efficacy. Fruit quality was assessed at 3 and 6 month storage intervals and over a 2-week ripening period at 22 °C. For all cultivars, the production rates of CO2, ethylene, and volatiles, as well as increases of IEC and decreases in firmness were inhibited or delayed by sprayable 1-MCP treatment. These effects were comparable to the postharvest 1-MCP treatment and were maintained during storage. The results of these experiments suggest that sprayable 1-MCP could be an additionaal tool for maintaining apple fruit quality. However, the sprayable formulation used in this study caused 100% incidence of skin damage to `McIntosh' and a slight amount to `Empire' (<5%). Lesions were halo-like, centered around lenticels, and tended to be more severe near the calyx. No skin damage was observed in `Delicious' or in fruit treated with the adjuvant only or postharvest 1-MCP.