Many studies have looked on the changes induced by oxygen in red wines and claimed small amounts of oxygen to promote balanced tannicity, more fruit aroma, and enhanced color. Oxygen-triggered reactions in red wines include the oxidation of catechol-containing phenolics yielding highly reactive quinones and hydrogen peroxide, the oxidation of ethanol to acetaldehyde, and eventually the formation of anthocyanin derivatives such as ethylidene-bridged anthocyanin-proanthocyanidin-oligomers, vitisin B, and hydroxyethyl-anthocyanin-derivatives. The knowledge of components, their reactions, and their sensory impact in red wine increased over the last decades. Accordingly, it is feasible to implement monitoring processes that allow controlling the oxygen-induced reactions during red winemaking. Based on different grape varieties and winemaking operations several red wines were produced with and without the continuous addition of oxygen by means of micro-oxygenation. During alcoholic fermentation vitisin B and ethylidene-bridged anthocyanin-catechin dimers were formed rapidly due to the acetaldehyde produced by yeast. While vitisin B showed higher stability, the ethylidene-bridged dimers disappeared towards the end of fermentation resulting in hydroxyethyl-anthocyanin-derivatives or adducts of higher molecular weight. The application of micro-oxygenation also triggered the formation of vitisin B (up to 5 mg/L) and ethyl-bridged anthocyanin-proanthocyanidin-oligomers. External quantification using isolated compounds revealed up to 30 mg/L for the ethylidene-bridged malvidin-3-glucoside-catechin dimer, up to 10 mg/L for the double ethylidene-bridged malvidin-3-glucoside-catechin trimer, and up to 25 mg/L for a ethylidene-bridged malvidin-3-glucoside-(B-type)-proanthocyanidin dimer. Interestingly, an adjustment of the tannin to anthocyanin ratio during winemaking resulted in different ratios of vitsin B to ethylidene-bridged compounds after micro-oxygenation. An increase of the tannin to anthocyanin ratio by enhancing the maceration time of red wines favored the formation of ethylidene-bridged compounds. However, after six months bottle storage a decrease of 67 % in ethylidene-bridged compounds and a decrease of 40 % in vitisin B could be observed.

Understanding and controlling oxygen-induced changes in red winemaking

248th National Meeting (2014)

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