Loss of trans-resveratrol during storage and ageing of red wines

Background and Aims: The concentration of free trans-resveratrol in wine is expected to increase with storage because of hydrolysis of piceid (a bound form of resveratrol). This study measured resveratrol concentration in 16 Australasian red wines ranging from 1 to 6 years old, both initially and after a storage period of 16 months under ambient conditions. Methods and Results: During the study period, trans-resveratrol concentration decreased by an average of 76%. The decay in trans-resveratrol was first order over the tested range of wine source and vintage, with a mean trans-resveratrol bottle-storage half-life of 8 (±1 SD) months. Decay rate was remarkably independent of growing condition and year. Conclusion: The data suggest isomerisation of trans- to cis-resveratrol via residual enzymatic activity (rather than being catalysed by light or acid). Significance of the Study: In general, this may reduce the anticipated health benefits of the wine given that cis-resveratrol displays fewer health benefits than the trans isomer. © 2020 Australian Society of Viticulture and Oenology Inc.