Dynamic Controlled Atmosphere Isolated or Associated with 1-MCP and Elevated Storage Temperature Affect the Overall Quality and Anaerobic Metabolism of ‘Royal Gala’ Apples

This study aimed to evaluate the effect of static controlled atmosphere (CA) and dynamic controlled atmospheres (DCA), isolated or associated with 1‑methylcyclopropene (1-MCP) treatment, and increased storage temperature on the quality maintenance of ‘Royal Gala’ apples after long-term storage. Fruit were stored in the following conditions: (1) CA with 1.2 kPa O2 + 2.0 kPa CO2; (2) DCA by chlorophyll fluorescence (DCA-CF); (3) DCA by respiratory quotient 1.5 (DCA-RQ 1.5); (4) DCA-RQ 1.5 with 1‑MCP application; (5) DCA-RQ 2.0; and (6) DCA-RQ 2.0 stored at 1.5 °C, all with 1.2 kPa CO2. After 9 months storage at 1.0 °C (except the sixth treatment), plus 7 days shelf life at 20 °C, evaluations of overall quality, physiological disorders, and anaerobic metabolism were performed. Fruit stored in DCA showed better quality compared to CA, especially by reducing firmness loss and physiological disorder incidence. Storage in DCA-RQ, regardless of the level and 1‑MCP application, has greater effect on 1‑aminocyclopropane-1-carboxylate (ACC) oxidase activity and ethylene synthesis than DCA-CF and CA. However, when associated with 1‑MCP, DCA-RQ 1.5 resulted in higher decay incidence. Fruit stored in DCA-RQ 2.0 showed a higher concentration of anaerobic metabolism compounds, but in concentrations that were not harmful to the fruit. Storage at 1.5 °C under DCA-RQ 2.0 did not affect fruit quality. Therefore, DCA maintains better quality of ‘Royal Gala’ apples, which can be stored at 1.5 °C if DCA-RQ 2.0 is used, while 1‑MCP does not bring benefits for apples stored in DCA-RQ 1.5.