Effects of dynamic controlled atmosphere by respiratory quotient on some quality parameters and volatile profile of ‘Royal Gala’ apple after long-term storage

• Volatile composition of apples stored in dynamic controlled atmosphere was studied.
• Dynamic controlled atmosphere maintained higher firmness.
• Respiratory quotient 1.5 and 2.0 maintained high 2-methylbutyl acetate concentration.
• Dynamic controlled atmosphere by chlorophyll fluorescence decreased the main esters.
• Respiratory quotient 2.0 results in higher ethanol and ethyl acetate accumulation.

The effects of dynamic controlled atmosphere (DCA) storage based on chlorophyll fluorescence (DCA-CF) and respiratory quotient (DCA-RQ) on the quality and volatile profile of ‘Royal Gala’ apple were evaluated. DCA storage reduces ACC (1-aminocyclopropane-1-carboxylate) oxidase activity, ethylene production and respiration rate of apples stored for 9 months at 1.0 °C plus 7 days at 20 °C, resulting in higher flesh firmness, titratable acidity and lesser physiological disorders, and provided a higher proportion of healthy fruit. Storage in a regular controlled atmosphere gave higher levels of key volatiles (butyl acetate, 2-methylbutyl acetate and hexyl acetate), as compared to fruit stored under DCA-CF, but fruit stored under DCA-RQ 1.5 and RQ 2.0 also showed higher amounts of key volatile compounds, with increment in ethanol and ethyl acetate, but far below the odour threshold. Storage in DCA-CF reduces fruit ester production, especially 2-methylbutyl acetate, which is the most important component of ‘Royal Gala’ apple flavour.