Abstract
The oxidation of polyphenols in red wines during their aging involves very complex reactions but constitutes a real research challenge because it will modify their organoleptic properties. Certain routes of formation of the polyphenols oxidation products have been described in the literature. However, many studies remain to be done, particularly on the formation and identification of new oxidation compounds in red wines. During this thesis, accelerated aging and oxidation protocols were developed on Syrah red wines (chemical, enzymatic and heating oxidation). A global and semi-targeted approach using high resolution mass spectrometry made it possible to compare the natural and accelerated evolutions of Syrah wines (3 different vintages 2018, 2014 and 2010). This axis was supplemented by an electrochemical approach using cyclic voltammetry and making it possible, for the first time, to predict the sensibility of a red wine towards certain oxidative degradations.The hemisynthesis of enzymatically obtained dimeric catechin oxidation markers was performed and the structures of six of them were elucidated by NMR for the first time. Some of these markers were then identified in more complex extracts of seeds (Merlot, Tannat, Syrah) and in Syrah wines previously used. An effect of the berries ripening and the vintage of the wines was observed.Finally, the tannin oxidation products and their formation kinetics were studied in these same Syrah wines (2018, 2014 and 2010) and compared to the chemically oxidized 2018 Syrah wine. This study was carried out using chemical depolymerization followed by liquid chromatographic separation coupled with a mass spectrometer (UHPLC-ESI-MS / MS) and made it possible to better understand the evolution of tannins in wines.