Estimation of the distribution of enantiomers of γ-decalactone and γ-dodecalactone in malt whisky

Abstract

Lactic acid bacteria generate precursors of γ-lactones, which contribute to sweet and fatty flavour, from unsaturated fatty acids. In this study the distribution of enantiomers of γ-decalactone and γ-dodecalactone in malt whiskies were studied using multi-dimensional GC in an effort to elucidate the mechanism of formation of these lactones. The enantiomeric excess of these lactones was within the range of -10 to 30%. Furthermore, racemic methyl-10-hydroxystearate was synthesized and optically resolved by chiral-phase HPLC. The chirality of γ-dodecalactone produced was dependent on the chirality of the hydroxy fatty acid or its methyl ester supplied as the substrate, based on the results of a series of experiments in which the acid or the ester was supplied to distiller's yeast.