Carbohydrate-flavour conjugates in wine

Although flavour glycosides have been reported in wine, the possibility that they might contribute to perceived flavour by being hydrolysed in the mouth during consumption has not been previously documented. The release of hexanol from hexyl beta-Dglucoside was studied in-mouth by measuring hexanol in expired air with atmospheric pressure ionisation¯mass spectrometry. About 10% (0.2 mg) of the glucoside was hydrolysed over a 2 min period due to the activity of glucosidase enzymes from the oral microflora. Since wine contains ethanol, the inhibitory effects on alpha and beta glucosidases from different sources were ascertained using p-nitrophenyl glucosides and spectrophotometric determination. Enzymes from yeast and almonds were inhibited to a greater extent (70¯80%) than the Aspergillus niger enzyme (35%). Overall, the results show that there is potential for flavour glycosides to be hydrolysed in-mouth and therefore contribute to perceived flavour but further work in real food systems is needed to confirm this hypothesis.