Volatile ester suppression and recovery following 1-methylcyclopropene application to apple fruit

The effect of 1-methylcyclopropene (1-MCP) on biosynthesis of volatiles and fruit ripening in apple (Malus x domestica Borkh.) was investigated using 'Golden Delicious', 'Jonagold', and 'Redchief Delicious' fruit. Application of 1-MCP to 'Golden Delicious' at the preclimacteric stage effectively inhibited ripening as determined by decreased expression of genes for 1-amino-1-cyclopropane carboxylic acid (ACC) oxidase (ACO), and ACC synthase, ACO protein content, climacteric ethylene production, respiration, and volatile ester biosynthesis. Exogenous ethylene applied after 1-MCP treatment did not induce ethylene production, respiration, or volatile production. Activity for alcohol acyltransferase, which catalyzes the final step in ester formation, was demonstrable for 1-MCP-treated fruit, indicating no strict limitation on ester formation is imposed by this enzyme and that ester formation in 1-MCP-treated apple fruit is at least partially limited by reduced substrate synthesis. Once volatile ester formation had been suppressed by 1-MCP, the recovery of volatile synthesis required approximate to 3 weeks for 'Jonagold' and 4 weeks for 'Delicious' when held in air at 22 degrees C. For the first 2 months of storage at 0 degrees C in air, 'Jonagold' and 'Delicious' required approximate to 3 weeks holding at 22 degrees C for volatile biosynthesis to initiate; after 5 months in refrigerated storage, volatile formation was evident at the time of removal from cold storage. For 'Jonagold' fruit held in controlled atmosphere (CA) storage for 2, 5, and 7 months at 0 degrees C, at least 3 weeks holding at 22 degrees C were required for volatile formation to begin to recover. The maximal amount of volatile formation was reduced 50% by 1-MCP relative to nontreated control fruit. CA storage had a similar impact on maximal volatile formation. The marketing of 1-MCP-treated fruit soon after treatment might result in the delivery of fruit to the consumer with little likelihood of recovery of volatile ester formation prior to consumption.