Effect of dynamic controlled atmospheres on volatile compound production in 'Granny Smith' apples

This study investigated the effect of dynamic controlled atmospheres (DCA) on the production of volatile compounds in 'Granny Smith' apples. Fruit were stored in DCA (0.3-0.5 kPa O₂ + 1kPa CO₂) for 12, 16 and 20 wks at -0.5°C, air was used as the control. Gas chromatography-mass spectrometry (GC-MS) was used to analyze volatile compounds from the pulp of the fruit. Total amount of volatiles detected in the control fruit samples were significantly (p<0.05) higher than those exposed in DCA. Production of 1-butanol, 1-hexanol and 1-hexen-ol by fruit stored in DCA were 25, 45 and 27%, respectively, of the amounts detected in the control. DCA treatments also resulted in higher emission of ethanol compared with fruit stored in air. Production of 2-methylpropyl acetate by DCA stored fruit was 19% of that produced by the control fruit. Aldehydes emissions were lower in DCA compared to control fruit. Esters were the main volatiles detected (50%) with the highest emission obtained in the control treatment. The known characteristic flavour volatiles in apples, ethyl hexanoate and hexyl acetate were significantly lower in DCA stored fruit, however, ethyl-2-methylbutyrate was notably higher compared to the control treatment. Titratable acidity loss was significantly reduced by DCA treatments compared to normal regular air storage.