Published by Sally on December 1, 2009

A shorter version of this article first appeared in Wine and Spirit magazine in 2006, since merged into Harpers Wine and Spirit.

Micro-oxygenation, or mox to its mates, is a controlled, periodically continuous addition of tiny amounts of oxygen to wine, usually red. Among other things, it’s argued to have the same effect as the aeration of wine during racking (taking wine off its sediment and putting in a clean container), and barrel maturation.

Forget the new world being leaders in technical winemaking innovation. Mox was devised in 1991 by Patrick Ducournau, of Domaine Mouréou/Chapelle Lenclos in Madiran, as a way of softening the tannins of his home grape variety, tannat, which has legendary tannins.

Benefits include the stabilisation of colour, the building up and softening of structure and the lessening of stinky, reductive notes

It’s now widely used across the winemaking globe, on tannic grape varieties. Mox and pinot noir are unlikely ever to be best buddies. Justin Knock, at the time one of the Foster’s Group winemakers said: “you use mox on tannic grape varieties, for softer styles of red wine to drink at an earlier age, and you can use it on your best wines to make them more complete.” He outlined the technique’s benefits as including the stabilisation of colour, the building up and softening of structure, the lessening of stinky, reductive notes during tank maturation, and the amelioration of ‘green characters’. He said it was used at Rosemount, Lindemans and Wynn’s.

The fundamental risk is oxidation. Peter Taylor, global winemaking development director at Foster’s Group said: “you need your quality control spot on because you’re doing something different. We taste and analyse more regularly than we would normally. We don’t know how much oxygen a wine needs during its development, so need to monitor carefully.”

The argument goes thus: racking saturates a wine with oxygen, which is then gradually absorbed and used by elements in the wine. A controlled amount is thought to be more predictable than racking, for example, somewhere between 60 and 80ml/litre/month before MLF (malolactic fermentation) and a very low rate after MLF, 1-2ml/litre/month, for up to six months, might be common. But it isn’t known how much oxygen a wine needs, so it’s still work in progress.

It can kill the fruit, over-oxidise the tannins and increase volatile acidity

Oxidation isn’t the only risk. Jacques Lurton, of international winemaking company J&F Lurton warns “Mox is a risky technique, it can kill the fruit, over-oxidise the tannins, increase volatile acidity by over three times if it’s not well managed and anticipated; [you may only see] the consequences six months later.”

He still uses it though, to stabilise colour, which is done between fermentation and MLF and can increase colour by up to 30% with apparently little effect on tannins. The oxygen fixes the colour to a tannin molecule. Otherwise the ‘unfixed’ colour molecules drop out.

Lurton said: “we don’t use mox during wine maturation after MLF, because it makes the wine too tight. It’s risky, you get a ‘tannic sensation’ and it stays in the wine forever.” He said they prefer to build structure in the vineyard with such techniques as water stress.

Temperature is something else to watch. If temperature is cold then reactions are slower and oxygen absorbs more easily which is an additional oxidation risk. It can take several days, even with close monitoring, to pick up the effects due to cold temperature lag time, by which time of course it could be too late. Ideal temperature range is thought to be 13 to 18°C.

Micro-oxygenation is not necessary

Not everyone is in favour of using micro-oxygenation. Nicholas Buck, director of Te Mata Estate in Hawke’s Bay, New Zealand prefers the low-tech approach, saying “Mox is not necessary. We’re very traditional, elevage en barrique with topping and racking, so our wines get plenty of oxygen over time. We achieve the same that mox tries to rush. With cellar temperature fluctuation, and two winters in barrel, we achieve lovely resolution of tannins with development of further flavours and aromas, and the wine is stable. Nice tannins, extracted well, can handle quite a lot of oxygen exposure. If you get the tannin right in the vineyard, and it’s right in the winemaking, you achieve long, elegant, even tannins.”

So mox helps improve the drinkability of young reds. And it is an addition of oxygen in a controlled fashion but we’re still experimenting to discover what the exact correct amounts should be, but we know they vary by grape variety and vintage.

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