Effect of long-term controlled atmosphere storage enriched with ethanol or hexanal vapour on primary and secondary aroma compounds of ‘Braeburn’ and ‘Granny Smith’ apples

Abstract

The aim of this research was to study the effects of ethanol or hexanal enriched atmosphere focusing on primary (PA) and secondary aroma (SA) volatiles of 'Braeburn' and 'Granny Smith' apples. Apples were stored for 7 months under three conditions: controlled atmosphere (CA, 2 kPa O₂,1 kPa CO₂), CA with hexanal or CA with ethanol vapour (55 µgL⁻¹ air). Volatile profiles were analyzed over 7 days of shelf-life at 20 °C. The results showed large differences between PA and SA profiles. The SA of both cultivars showed higher levels of aldehydes and alcohols, while PA was characterized by higher contents of hexyl and butyl esters. The most influential compounds were hexyl 2-methylbutanoate, hexanal, and 2-methylbutanal for 'Braeburn', and 2-methyl-1-butanol, butanal, and hexanal for 'Granny Smith' apples. The effect of the addition of hexanal and ethanol to CA on the PA and SA profile after storage was dependent on the cultivar and shelf-life period. The most pronounced effect was observed with hexanal treatment on the PA of ‘Braeburn’ apples, where hexanal treatment enhanced key aroma-active compounds, such as hexyl butanoate and hexyl hexanoate. Both vapor treatments induced the formation of 2-pentanone and 2-pentanol, indicating lipid peroxidation in both apple cultivars. Prolonged exposure to ethanol or hexanal vapors in CA can modulate the synthesis of key volatile compounds in PA and SA, potentially offering promising applications in the flavor and food industries.