Oxygen has many roles and impacts on wine, starting with the harvest and through to the ageing process. Oxygen is essential for the tannins to soften and for the colour to intensify and stabilize. However, too much can denature the wine.
Oxygen offers certain advantages and disadvantages depending on the quantity and period where it is added. It can react with various wine compounds, favour certain enzymatic reactions and the development of microorganisms. Its addition should be modulated according to the stage of production, and also in relation to the wine's quality and the type of product desired.
5.5.1.a Oxygen during ageing
What are the different types of oxygen input?
Two types of oxygen input occur during the ageing process. First, there is rapid exposure when operations such as pumping over or racking are carried out. This is when oxygen accumulates in the wine before being consumed.
Second, there is the controlled addition of oxygen, where the quantity of oxygen supplied is similar to the rate of consumption. This is the case with oxygen transfer through the barrel under pressure or when micro-oxygenation is practised.
Estimating the wine's requirements
On average, red wines need about 80 mg/L of oxygen and white wines about 30 mg/L. However, these values are highly dependent on the primary material. For example, a very tannic wine can withstand more oxygen.
It is necessary to reduce the sudden addition of oxygen with sensitive grapes, i.e. those with few reactive tannins that will therefore not benefit from much exposure to oxygen. This is the case with overripe grapes, for example.