🍷 Micro-oxygenation

Micro-oxygenation is a winemaking technique in which minute, measured amounts of oxygen are introduced into wine. According to the International Organisation of Vine and Wine (OIV), the rate at which oxygen is added must be lower than the rate at which the treated wine consumes it, so that oxygen does not accumulate in the wine during treatment. In the equipment described in a technical review, a ceramic diffuser in the tank turns the dosed oxygen into a stream of fine bubbles that disperse rapidly into the wine.

The OIV lists what oxygenation is used for: to help stabilise the colour and the maturation of red wines (oxygen promotes acetaldehyde, which reacts with flavanols and anthocyanins to form new pigments that are more stable and more intensely coloured), to reduce volatile sulphur compounds such as hydrogen sulphide, to reduce vegetal aromas and to make fining easier. The technical review adds improved palatability and tannin softness, and notes that the method was developed by Patrick Ducournau and Thierry Lemaire of the French company Oenodev.

The idea comes from comparing wine matured in tank and in barrel. In a barrel the wine is constantly exposed to small amounts of air, which enters through the bunghole, during topping and arguably through the staves; in a tank, racking exposes it to large volumes of air for short periods. Micro-oxygenation is designed to dose wine with oxygen at levels that do not encourage microbial activity.

The OIV Code distinguishes three variants. In micro-oxygenation, for colour stabilisation and for improving a red wine during ageing, the doses are of the order of 1 to 5 mg of oxygen per litre per month, depending mainly on the wine's anthocyanin and polyphenol content and its free SO2. Macro-oxygenation uses higher doses over a shorter period, at the end of fermentation and up to the first racking, and nano-oxygenation adds very small amounts, of the order of tens or hundreds of micrograms per litre, at regular intervals.

Why it matters to you. According to the OIV, micro-oxygenation is preferable for wines with a high content of free anthocyanins, it is not recommended above 22 °C (excessive oxidation) or below 8 °C (oxygen accumulation), it must not be used to remove excess sulphur dioxide, and the microbiological stability of the wine, especially with regard to Brettanomyces bruxellensis, must be monitored.