Oxygen Reduction in Winemaking

Oxidation gets a lot of attention in winemaking — and it should! WineMaker magazine has covered oxidation issues from several different angles over the past few years. While some presence of oxygen in wine contributes positive effects, most of the time the home winemaker is excluding oxygen to avoid the browning, aldehyde formation, and spoilage that may result from oxidation. In chemistry, though, oxidation is just half the story! In a yin-and-yang condition that is learned by every chemistry student, any oxidation reaction is more properly characterized as a “half reaction.” That is because the other half reaction, allowing the entire process to occur, is the reduction half reaction. When I used to work in environmental chemistry, it was commonly noted that to get something clean you have to get something else dirty. In similar fashion, to get something oxidized, something else must be reduced. To provide a basis for the further discussion of reduction in wine, we need to delve into basic chemistry a bit. The pair of half-reactions that make up an oxidation-reduction complete reaction (abbreviated redox) are