2017 ASHS Annual Conference

Postharvest management of apple (Malus domestica Borkh.) fruit ripening using controlled atmosphere (CA) cold storage can be enhanced as CA oxygen concentration is decreased to close to the anaerobic compensation point (ACP). Monitoring fruit chlorophyll fluorescence is one technology available to assess fruit response to low O₂ CA conditions while avoiding anaerobiosis. As apple fruit response to CA is also determined in part by CO₂ concentration, studies were conducted with ‘Golden Delicious’ and ‘Honeycrisp’ to examine fruit response to O₂ storage conditions at or near the ACP with various CO₂ concentrations. ‘Golden Delicious’ apples were held at 0.5 ^oC for 48 h after harvest during which time some fruit were exposed to 42 μmol L^-1 1-methylcyclopropene. CA was established by 96 h after receipt. Fruit chlorophyll fluorescence increased when O₂ kPa decreased to ~0.3. ‘Golden Delicious’ fruit developed external and internal disorders when stored in CA with 5 kPa CO₂. CF did not change during storage although injury occurred. Disorder incidence increased as O₂ concentration decreased and with 1-MCP treatment. Some aspects of fruit quality were enhanced as CA O₂ decreased. ‘Honeycrisp’ fruit were held 7 d at 10 ^oC then at 2.8 ^oC. Some fruit were exposed to 42 μmol L^-1 1-MCP the day of receipt. CA was established 48 h after transfer to 2.8 ^oC. Fruit chlorophyll fluorescence increased when O₂ kPa decreased to ~0.3 kPa O₂. Internal disorder incidence increased as CA O₂ decreased and also with 1-MCP use. CF did not change during storage. Some aspects of fruit quality were enhanced by storage in lower O₂. Low O₂ did not impact incidence of low temperature disorders. Results indicate some aspects of fruit quality for both cultivars are enhanced by storage in the lowest O₂ concentrations although CF may not provide an indication of fruit stress that can result in physiological disorder development.