Relating expert quality ratings of Australian chardonnay wines to volatile composition and production method

Abstract

Chardonnay is a neutral grape variety offering a diversity of wine styles that are popular among consumers. The links between wine production methods and Chardonnay wine volatile composition, as determinants of quality, require further elucidation. Over 80 commercial Australian Chardonnay wines were assessed by expert panelists who were asked to define four distinct levels of quality in a blind tasting. Wine aroma volatiles in each wine were analyzed by solid-phase microextraction-gas chromatography-mass spectrometry, and multivariate statistical techniques were used to examine the relationship between volatile composition and quality as defined by the experts. Of 39 aroma compounds quantified, nine volatiles (including cis- and trans-oak lactones, furfural, and diethyl succinate) correlated significantly and positively with Chardonnay wine quality, while 11 volatiles (including fruity esters and monoterpenoids) correlated negatively. Compounds associated with oak contact and malolactic fermentation were present at highest concentrations in higher-quality wines as perceived by wine experts. Lower scores were assigned to younger but less complex wines, which were richer in fruity esters and other grape-derived compounds. A model was developed using partial least squares regression based on these results, which permitted classification of the Chardonnay wines into high-, medium-, and low-quality brackets depending on their relative concentrations of cis- and trans-oak lactone, ethyl lactate, and 2-methyl-1-propanol (positive) and of 1-propanol and 1-hexanol (negative). There was a significant and positive correlation (r = 0.469, p <0.0001) between retail price and quality score, underlying the usefulness of price as an indicator of quality, although it failed to entirely explain quality (as judged by experts) and should therefore be used in conjunction with other quality cues.