Winemaking
Micro-oxygenation
Dosing tiny, controlled quantities of oxygen into a tank — developed for Tannat, and not the same as barrel ageing.
The short answer
Micro-oxygenation introduces measured quantities of oxygen into a tank through a diffuser, at rates measured in millilitres per litre per month. The purpose is to drive the tannin and colour polymerisation that would otherwise happen slowly in barrel.
Overview
It was developed in Madiran in the early 1990s to deal with Tannat, the variety with the highest measured tannin of any widely planted grape.
It is regularly described as a way of imitating barrel ageing. That is not accurate, and the difference is instructive.
How it works
The mechanism, at the scope it has actually been established.
Oxygen is delivered continuously at a controlled rate, which promotes reactions between anthocyanins and tannins to form stable polymeric pigments — the same chemistry as in a barrel, at a rate the winemaker sets.
It can also help consume reductive sulfur compounds and modify vegetal character.
What it does not do is contribute oak-derived compounds, or reproduce the lees contact and gentle concentration a barrel provides. It is one component of barrel ageing, isolated.
Dosing is a precision operation and over-dosing oxidises the wine or encourages spoilage organisms, so it is monitored closely.
It is permitted in the EU and elsewhere within limits, and is widely used in mid-priced red wine production.
Frequently described as a cheap substitute for barrel ageing. It replicates one of several things a barrel does, and WineHQ says which one rather than repeating the comparison.
Sources
More in winemaking
Winemaking
Fermentation
Yeast converting sugar into alcohol and carbon dioxide — the step that makes wine wine.
Winemaking
How red wine is made
Fermenting grape juice in contact with the skins, which is where colour and tannin come from.
Winemaking
How white wine is made
Pressing the juice off the skins before fermentation, then fermenting the clear juice.