The Cellar Dweller
Micro-ox: Wave of the future?
Method of softening the impact of harsh tannins has now spread tomost wine producing regions.
By Gary Strachan L
ast year I wrote about the good and bad effects of oxygen during winemaking in the article ‘Sleeping with the Enemy.’ Oxygen plays a role in the stabilization of colour in red wines and in the flavour maturation of tannins. On the other hand, we know that excess exposure of wine to oxygen during various stages of production can create premature oxidation and excessive decline in fruit character.
Where do we draw the line between beneficial amounts of oxygen and excessive uptake?
I will target this discussion mainly on red wines, because of the influence of oxygen the on development of colour and astringency. Every
Control panel for a micro-oxygenation system.
winemaker is aware of the importance of skin extraction for red wine colour development. There must be at least a dozen ways to accomplish this, all of which add air to the must during cap manipulation. None of them controls aeration. It’s mostly a hit-or-miss situation of punching down, submerging, or pumping over. Even when the process is computer- controlled for timing and duration, the winemaker has little or no knowledge of how much oxygen is dissolved in his wine during each submergence. Micro-oxygenation (micro-ox) is the controlled and measured addition of
small amounts of oxygen to wine. The process was invented in France as a method to soften the sensory impact of harsh tannins, and has now spread to most of the wine producing regions of the world.
The oxygen additions are deliberate and generally involve the use of specialized equipment as opposed to uncontrolled additions of air which occur during operations such as pumpovers.
Micro-ox additions are usually of the order of 1-4 mg/L per month, as opposed to short term aerations (macro-ox?) which can be in the order of 2-4 mg/L per day. Dependent on wine temperature, the limiting factor for oxygen uptake in wine may well be the solubility of oxygen, which is about 6 mL/L of wine at 20 C, but will increase to about 7 mL/L if the temperature is dropped to 5 C .
Unfortunately, it can be difficult to measure the low concentrations of oxygen which are typically present in wine.
Oxygen should be added at a rate that will cause no bubbles to appear. All added oxygen should dissolve as it is added.
The stages of flavour development during micro-oxidation. Note the negative effects of over treatment. Figure adapted from D.A. Blaauw, Cape Wine Academy.
22 British Columbia FRUIT GROWER • Summer 2012
If oxygen is added by aeration, there will be bubbles, because air contains roughly 80 per cent nitrogen, which is sparingly soluble in wine.
Whenever possible, use pure oxygen in order to facilitate accurate
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