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Micro-Oxygenation: A Special Technique Used For Tannic Varieties

Micro-Oxygenation: A Special Technique Used For Tannic Varieties


Tannat is one of the most tannic grape varieties in the entire world. Approaching it at its young stage would be almost impossible unless winemakers didn’t learn how to deal with the tannic variety.

In fact, producers developed and implemented unique techniques through the years. The usual de-stemming and soft pressing wouldn’t be enough to ensure approachable Tannat wines since an early stage of their lives.

We are here today to discuss micro-oxygenation. Originally, the technique was developed as a response to the fierce tannins of Madiran’s Tannat grape. In fact, micro-oxygenation seems to be particularly successful for variety with high tannin levels.

It also works with wines high in tannin but relatively low in anthocyanins like Sangiovese for instance.

Are you ready to discover this unique techinque?

Micro-Oxygenation: What It Is And How It Works

What is micro-oxygenation and what is used for?

It’s a vinification technique, also known as microbullage (colloquially as “microx” or “mox”), invented by the winemaker Patrick Ducournau in 1990 in Madiran.

Generally speaking, the method was authorized by the European commission in 1996 and is used to control the aeration in tank mainly, but by no means exclusively, on red wines.

The main principle behind the micro-oxygenation is that all wines require oxygen and its aim is to allow winemakers to deliver controlled levels of oxygen throughout the winemaking processes.

It has been stated that the introduction of oxygen through micro-oxygenation appears to accelerate the aging process. However, this is contested by those who make the equipment and promote its use (for obvious reasons…).

Figure 1: Assessing some wine in the cellar (, 2020)

The effect of this technique depends on the period of time and on the amount of oxygen to which it’s added.

The micro-oxygenation apparatus consists of a system of two chambers and valves connected to a cylinder of oxygen. The gas is moved into a first chamber that is calibrated to the volume of wine. It then moves into a second chamber and is delivered into the wine.

Thanks to a timer, the periodic injection is controlled and delivered into a precise dose. This way everything is under winemakers’ control.

The gas passes through a small polyamid tube into the tank and diffuses through a porous ceramic stone hung, near the bottom of the vessel.

A typical dosage rate is between 0,75 and 3 cc of oxygen per liter of wine per month. The overall treatment may take 4 to 8 months.

This technique might be tricky as there are no general guidelines to follow. In other words, there are no precise rules for how much micro-oxygenation a wine can take. That means that winemakers have to guess and monitor the process carefully by regular tasting.

The Function Of Micro-Oxygenation

The technique has several functions:

  • At the early stage of the alcoholic fermentation, it builds a healthy yeast population and helps avoid a stuck fermentation;
  • It helps to maintain yeast viability, minimizing the production of sulfites which may later cause reduction issues;
  • It mirrors the effect of oxygen on wines treated to barrel maturation. As we know, there is a continuous interaction between wine and oxygen when it’s stored in oak barrels. Stored in tanks this doesn’t happen. In fact, the wine is exposed to oxygen violently only during racking; This technique, with the addition of oak chips or inner staves, can provide a cost-effective alternative to oak barrels;
  • It seems to favor the polymerization of tannins and the retention of pigmented tannins (resulting in a softer taste and more stable color);
  • Apparently, this is also an effective remedy for green or vegetal characters that are the result of underripe fruit (although there is no evidence of this);
Figure 2: A bottle of Tannat, very likely to be produced with micro-oxygenation technique (, 2015)


Even though the technique is quite recent, more and more producers are using it.

By the beginning of the 21st century, approximately 2,500 micro-oxygenation units were in use in France (particularly in Bordeaux) and in at least 11 countries on 5 continents.

The “biggest fan” of micro-oxygenation is Chile, where it’s particularly appreciated for its ability to moderate the greenness character found in some Chilean red wines.

The technique is particularly suitable for fashioning wines for short to medium-term consumption from tannic or potentially reductive grape varieties.

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