RED WINE BARREL AGEING ON LEES. ADVANTAGES OF OXIDATIONS UNDER REDUCTIVE CONDITIONS.

During wine ageing, oxido-reductive reactions are mainly determined by the frequency of oxygen additions. Oxidations are caused either by the exposure to oxygen during racking, headspaces, or other operations, or during micro-oxygenations by diffusing pure oxygen slowly into the wine at pre-determined rates. Today, the different effects of oxygen are better understood. For example, it is known that the resulting transformations are essential for colour stabilization and to smooth tannins in red wines. However, in spite of the enhancing effects of oxidations, some undesirable effects can not be neglected. At international level, markets are focussed on fruity wines with fresh, intense colours and round tannins, which allow these wines to be consumed early. Nevertheless, oxidations often cause decreases in fruity aromas. At the same time, depending on the frequency and intensity of oxygen additions, the phenolic structure and colour of the wine can evolve prematurely. This leads to thinner wines and dryness caused by the precipitation of the most polymerized tannins, and the colour evolves towards brick-red hues from colour degradation. In fact, the challenge of oxidative ageing lies in both the adjustment of oxygen additions to the wine phenol profile, as well as the utilization of reducing substances allowing to limit the unwanted effects of oxygen, such as colour destruction and loss of fruity aromas. If modern wine ageing had to be summarized in few words, we would choose “Oxidations under Reductive Conditions”. However, this concept is not innovative but rather the return to ancient practices, which recommended early ageing combined with extended yeast-lees contact. This procedure is still in use in Burgundy.