Influence of storage conditions on the composition of red wines

Knowledge of the influence of temperature on the chemical composition of red wines should be useful, given that inappropriate storage is likely to shorten shelf life while decreasing wine quality. Putative markers of ageing for red wines stored for two years at two different storage temperatures (cellar vs. domestic) were investigated using MS-based untargeted metabolomics, and further confirmed by additional metabolite profiling. Of the 10k features extracted from the metabolomic dataset, those significant in terms of their ability to distinguish between the two storage conditions were mostly pigments and other phenolics, several of which were annotated with 1st level identification. Tentative identification of the remaining chromatographic peaks was made by using spectral features, literature information about chromatographic properties and mass spectra records from databases and an internal database for the wine metabolome based on the bibliography. The results of multivariate analysis clearly showed that wines stored in the cellar changed little even after two years of storage, while wines stored in typical domestic conditions developed approximately 3-4 times faster. Ageing in domestic conditions appeared to induce an accelerated decrease in native anthocyanins, while specifically promoting the formation of pinotin A-like pigments. Interestingly, we observed a temperature-dependent pathway involving the addition of bisulfite to the flavanols and leading to the formation of several catechin and proanthocyanidin sulfonates, along with hydrolysis reactions involving various phenolics, including flavonols. The temperature-dependent sulfonation process of flavanols was reproduced in a model wine system, making it possible to isolate the main reaction products. Two main metabolites were structurally elucidated using NMR measurements and confirmed to correspond to the products found in wines aged in domestic conditions. Epicatechin 4β-sulfonate and procyanidin B2 4β-sulfonate are suggested as promising markers present in wines stored at elevated temperature.