Aroma volatiles and sensory quality of organically-grown apple cultivars after dynamic controlled atmosphere (DCA) storage and comparison with CA-stored fruit with and without 1-methylcyclopropene (1-MCP)

Abstract

Long-term storage of many apple cultivars can be especially challenging for organic production where use of 1-methylcyclopropene (1-MCP), a crop protectant that controls ripening is disallowed. For many cultivars, controlled atmosphere (CA) storage alone, is inadequate for managing disorders and ripening. Dynamic controlled atmosphere (DCA), by determining the pO2 just above the lower oxygen limit (LOL), permits the use of lower pO2 setpoints without any negative impacts of anaerobiosis. Consequently, DCA can replace 1-MCP for maintenance of fruit quality. The goal of this study was to determine where this held true for a selection of old and new release organically-grown cultivars in the context of sensory perception. Cultivars included ‘Enterprise’ and ‘GoldRush’ harvested in 2018 (year 1), and ‘Honeycrisp’, ‘Golden Delicious’, ‘Jonagold’, and ‘Fuji’ harvested in 2020 (year 2). The LOL was monitored for DCA using chlorophyll fluorescence (CF) and compared with conventional static CA with or without 1-MCP treatment at harvest. DCA storage suppressed ripening to a similar level as 1-MCP plus CA in both years as indicated by reduced ester biosynthesis and, for some cultivars, maintenance of flesh firmness. However, ripening suppression did not impact the overall sensory preference of ‘Enterprise’, ‘Honeycrisp’, or ‘Fuji’, as all cultivars retained firmness and tartness regardless of storage regime and even negatively impacted it for ‘Goldrush’, an especially tart and firm cultivar. Sensory liking of ‘Golden Delicious’ and ‘Jonagold’ which have more typical diminishing firmness and acid profiles were most benefited by either 1-MCP treatment or DCA storage. The results highlight that use of storage technologies that suppress ripening beyond conventional CA storage are best employed on cultivars with more conventional softening and acid metabolism profiles as opposed to new cultivars that were selected primarily against these ripening phenotypes. The results also demonstrate the value of sensory evaluation compared with instrumental measurements to reveal the influence of different storage regimes on human perception.