Controlled Atmosphere (CA) and Dynamic CA-Chlorophyll Fluorescence (DCA-CF) Storage of 'Gala' Apple

Stem end browning (SEB) in ‘Gala’ is becoming a significant problem for storage operators as volumes of fruit and hence storage periods are increasing. In this study we have investigated the effects of air, CA and DCA-Chlorophyll Fluorescence as well as the use of 1-methylcyclopropene on SEB incidence and severity taking two approaches. In the first, ‘Gala’ trees in a western NY orchard were either untreated or treated with the preharvest plant growth regulator Harvista™ (1-methylcyclopropene; 1-MCP) 1 week prior to the first harvest, spot picked for color early in the harvest window and then strip picked the following week. Fruit were cooled to 0.5 ^oC overnight and then either treated or not with SmartFresh (1-methylcyclopropene; 1-MCP) and kept in air, CA or DCA-CF (harvest 1 only) for up to 6 months. In the second, fruit were obtained from four orchards and stored in CA and DCA-CF after half of the fruit were treated with SmartFresh. In both experiments, O₂ partial pressures were kept 0.2 kPa above the fluorescence-derived low O₂ limit of 0.3 kPa, plus 1 kPa CO₂, while CA conditions were 2 kPa O₂ and 2 kPa CO₂. In experiment 1, fruit were stored for 3 and 6 months, and in experiment 2 for 5 and 8 months. After removal from storage, fruit were kept at 20 ^oC for 1 and 7 days and assessed for quality and storage disorders. Fruit stored in DCA-CF had negligible SEB incidence at 3 months while fruit stored in air and CA all had higher levels with greater severity. After 6 months of storage, the level present in DCA-CF was similar to CA at 3 months, although the intensity was only slight. Use of Harvista™ lowered the level of SEB present in both CA and DCA-CF. Core browning was controlled by DCA-CF. In the second experiment, SEB incidence ranged from 0% to 67% in CA, and 0% to 10% in DCA-CF storage at 5 months. DCA-CF storage markedly delays the development of SEB incidence and severity.