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
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