Exposure to hypoxia conditions alters volatile concentrations of apple cultivars

Abstract

Brief periods of hypoxia at ambient temperatures (20 °C) have potential for disinfestation treatments or as pre-treatments to maintain fruit quality during extended storage. Nine cultivars of apple (Cox's Orange Pippin, Fuji, Golden Delicious, Granny Smith, Pacific Rose, Red Delicious, Royal Gala, Splendour and Southern Snap) were exposed to hypoxia using an atmosphere of 100% carbon dioxide for 24 h at 20 °C. Quantitative and qualitative analyses of volatile compounds were undertaken after removal of fruits from a high-carbon-dioxide atmosphere and during 1 week at 20 °C. Concentrations of acetaldehdye, ethanol, ethyl acetate and ethyl esters were consistently enhanced by hypoxia, while concentrations of acetate esters and aldehydes were depressed. Cultivars varied considerably in response to high carbon dioxide, with Cox's Orange Pippin and Golden Delicious having the least and Fuji and Red Delicious the greatest enhancement in ethyl esters. Fruits exposed to hypoxia had larger odour unit scores than control fruits, suggesting that such changes in volatile concentration may affect aroma and/or flavour. Enhanced ethyl ester concentrations in fruits exposed to hypoxia may be due to increases in ethanol concentration that competitively inhibit formation of non-ethyl esters. There may also have been a change in ester-forming enzyme activity and/or substrate specificity of the volatile biosynthetic pathway. This study has shown that short-term exposure to hypoxia has the potential to change the aroma/flavour of apples. © 2000 Society of Chemical Industry