Ethyl 2-hydroxy-3-methylbutanoate enantiomers: quantitation and sensory evaluation in wine

Aim: To investigate chemical and sensory characteristics of ethyl 2-hydroxy-3-methylbutanoate in wines. Methods and results: Ethyl 2-hydroxy-3-methylbutanoate has been recently identified as a potential marker of lactic acid bacteria esterase activity. Enantiomers of this fruity ester were quantitated in 99 wines from various vintages and French regions using chiral gas chromatography (gamma-cyclodextrin phase). Analyses revealed the predominant presence of the R enantiomer in red and white wines, with a maximum R/S enantiomeric ratio of 94/6 in a 1993 red wine. Results also highlighted greater levels of the ester in red than white wines, depending on grape origin. The detection thresholds of the Rand S-form were estimated at 4 mu g/L and 1.5 mu g/L in water and 51 mg/L and 21 mg/L in red wine, respectively. Moreover, ranking tests made with levels found in wines did not show significant sensory differences. Conclusion: The concentrations found in wines were considerably below the detection threshold, indicating no direct effect of these compounds on fruity aroma modulation. The absence of significant difference in sensory tests demonstrates that ethyl 2-hydroxy-3-methylbutanoate does not contribute significantly to the fruity aroma of red wine. Significance and impact of the study: To our knowledge, no previous research had determined the enantiomeric distribution and the sensory characteristics of this compound in wine.