Effect of storage under extremely low oxygen on the volatile composition of ‘Royal Gala’ apples

The aim of this work was to assess the profile of volatile compounds in ‘Royal Gala’ apples stored under controlled atmosphere (CA), with O2 levels ranging from 1.0 kPa to as low as 0.5 kPa during 8 months (0.5 °C), followed by 7 days of shelf-life at 20 °C. Volatile compounds were collected via solid-phase microextraction (HS-SPME) and analysed by gas chromatography. Straight and branched-chain esters exhibited a distinct pattern. The emission of straight-chain esters decreased under extremely low O2 (0.5 kPa), while branched-chain esters were not significantly affected in such condition. 2-Methyl-butyl acetate, a significant contributor to the ‘Royal Gala’ aroma, was higher in intermediate O2 concentration, suggesting that lowering the O2 levels down to 0.7 kPa does not negatively affect the volatile composition of ‘Royal Gala’ apples, as compared to the standard CA (1.0 kPa O2). The remaining volatile compounds were not strongly affected by storing fruits under extremely low O2.