Fate of phenolic compounds in white wines obtained and stored in the presence of different antioxidants

This work aimed to evaluate the evolution of phenolic compounds during white winemaking process up to bottling and 12 months storage, together with the influence of different antioxidant strategies (e.g. fining on lees and addition of sulfur dioxide, ascorbic acid, glutathione, and chitosan) on the overall kinetics. To this purpose, a mass spectrometric approach has been adopted by using HPLC-MS/MS, in order to get new insights in the understanding of wine oxidation processes. Sulphonated compounds related to oxidation were identified (e.g. S-sulfonated glutathione, and tryptophol and indole-3-lactic sulfonates) and their production was revealed to occur after alcoholic fermentation or fining on lees and to increase after 10 months of storage. On the other hand, treatments with chitosan during winemaking seemed linked to the hydrolysis of hydroxycinnamates, releasing their corresponding hydroxycinnamic acids. Surprisingly, when present during storage in bottle a particular behaviour of chitosan was observed, where this biopolymer avoided the phenomenon of hydrolysis and showed higher inhibition against phenolic products of oxidation such as hydroxycaffeic acid dimers. Furthermore, the addition of ascorbic acid to chitosan-treated wines before bottling, reduced the generation of oxidations products and raised the production of GRP derived phenols, correlated to a better protection against oxygen. The absorption properties of chitosan with regard to phenolics also proposed to have some consequences on the evolution of wine browning. Based on these results, the knowledge about polyphenols fate may represent a useful approach to manage the antioxidant strategies during winemaking processes.