Technique

Understanding Oxygen and Oxidation in Winemaking

As budding winemakers, one important principle we heed is protecting juice (must) and wine from oxygen’s baneful effects. But then we learn that yeast needs a “little” oxygen for a good fermentation, that reds benefit from “some” aeration, and that some white varietals can be subjected to lots of oxygen with no ill-effects while others need complete protection. In this issue, we take a behind-the-scene look at oxidation phenomena in musts and wines to get a better appreciation of oxygen properties and chemistry in winemaking. Understanding O2 properties and chemistry and mastering O2 management will go a long way in helping you create superior wines. Note: in this article, “wine” will refer to either “must” or “wine” except where a distinction is necessary. Concentrations of compounds in wine will be denoted in square brackets; for example, [EtOH] denotes the concentration of ethanol (EtOH). Properties of oxygen There are two important oxygen properties to consider in winemaking: oxygen solubility and oxygen consumption. Oxygen solubility refers to the maximum amount of molecular oxygen (O2) that can be dissolved in wine to reach