Commercial Application of 1-Methylcyclopropene Affects the Storability and Disorders of ‘Empire’ and ‘Delicious’ Apples

This study evaluated the effects of 1-MCP on ‘Empire’ and ‘Delicious’ apples in commercial controlled atmosphere (CA) storage for 12 months, and in commercial cold storage for 6 months. Apples were harvested and delivered by growers to a local commercial storage facility. Four different grower lots were chosen for each of three ‘Empire’ and two ‘Delicious’ storage rooms. Fruit were treated with 1-MCP (~ 0.8-1.0 µL·L^-1) for 24 hours, while control fruit samples were held in a similar nearby storage room. Following treatment, control samples were placed with matching MCP-treated samples either into CA storage (2.5% O₂ + 2.5% CO₂ at 2.2 or 0^oC for ‘Empire’ and ‘Delicious’, respectively) or air storage at 0-1^oC. Initial maturity was relatively uniform among the grower lots, with internal ethylene concentration (IEC) averaging <1 µL·L^-1 for ‘Empire’ and 2-3 µL·L^-1 for ‘Delicious’. IEC was lower in apples treated with 1-MCP after air (3 or 6 months) or CA (6, 9, or 12 months) storage, but this effect was reduced after a 14 d ripening period at 22^oC, and less dramatic in fruit from CA than from air storage. Apples treated with 1-MCP were also firmer than non-treated fruit upon removal from storage, and this difference became greater with increased post-storage time at 22^oC (up to 4 lb differences). 1-MCP treated apples stored in air had higher soluble solids concentration (SSC) (up to 0.5% difference), while there was no significant effect of 1-MCP on SSC in fruit held in CA. Core browning developed in ‘Empire’ held in air for 6 months (up to 52% incidence) or in CA for 9 or 12 months (up to 34%), and in ‘Delicious’ after 9 and 12 months in CA (up to 27%). 1-MCP decreased the incidence of this disorder in ‘Empire’, but increased the incidence in ‘Delicious’. There was no significant effect of 1-MCP on the incidence of internal browning and storage rots, which developed in both cultivars.