Effect of fermentation on free and bound volatile compounds of orange juice

Aroma is one of the most important attributes of orange wine quality. The volatile compounds in orange wine mainly derive from oranges, yeast fermentation and compounds released from odourless glycosidic precursors present in the orange. In this study, free volatile compounds in orange juice and wine made from Citrus sinensis (L). Osbeck cv. Washington Sanguine were analysed by SPME-GC-MS. Bound fractions were isolated and extracted with methanol and Amberlite XAD-2 resin and then hydrolysed by almond β-glucosidase. Totals of 31 and 19 free volatiles were identified in orange juice and wines, respectively. Terpenes were the most abundant compounds in orange juice, while esters were quantitatively the dominant group in orange wine and most of them were compounds newly formed during fermentation, such as isoamyl acetate, ethyl hexanoate, ethyl benzoate, diethyl succinate, ethyl decanoate and ethyl laurate. In total, 11 and three released bound volatiles were found in orange juice and wine, respectively, and most of them were not found in free form. Only ethyl 3-hydroxyhexanoate and cis-carveol were found present in both the free and bound forms of orange juice. Copyright © 2009 John Wiley '' Sons, Ltd.