Methods for predicting and assessing flavour evolution during white wine ageing

Estimating future flavour evolution in wine generally requires quantitative analysis of a known precursor compound or forcible production using elevated temperature and/or lower pH with analysis of the produced volatiles. While it is understood that these methods are not always accurate, they can provide an indicative assessment of the magnitude of evolving species. However, due to the complex pathways by which some key odorants are formed, these predictive measures may not provide a compositionally relevant outcome, and do not provide any indication of future flavour evolution. Here, extracts derived from the winemaking by-product, grape marc, rich in monoterpene glycosides have been analysed by ‘predictive’ methods and also added to wine to provide a correlation with real-world evolution profiles. While analysis of a precursor molecule, geraniol glucoside, and acid-catalysed hydrolytic assessment of the extracts both provided good correlations with total flavour production in wine, neither were good predictors for final monoterpene composition in wines. Additionally, a single extract was monitored over 36 months in two different base wines and at two different concentrations to gain a better understanding of hydrolysis kinetics, which was also explored computationally. The generation of first-order rate curves provided a mechanism to determine reaction half-lives for the hydrolysis of geraniol glucoside and related to the monoterpene composition in wines.