OXYGEN AND AGING

Aging, specifically red wines, has been characterized as "controlled oxidation". More correctly stated as "controlled oxygenation".

Some air (O2/Oxygenation) is very necessary so that red wines will develop, becoming more supple, less tannic, developed. Some is also necessary to enhance wanted ester/aromas.

Too much (Oxidation), at the wrong time, is harmful, resulting in browning, loss of fruitiness, build-up of volatility. Too much develops unwanted esters/aromas.

Oxygen helps phenols (tannins) polymerize, link-up, becoming softer, the wine more supple.

The question is when to incorporate air/oxygen and how much effect is observed.

Oxygen during skin maceration: There is noticed some polymerization of phenols during early maceration but this is retarded by the trapped CO₂ (carbon dioxide) evolved during ferment. This vigorous punching down of the skin cap also helps to slow down ferment and to lower fermentation temperatures.

There is greater polymerization with extended fermentation after the end of sugar fermentation.

So, with big, tannic grape musts, some, albeit small amounts of polymerization is observed after extended fermentation of 3-6 weeks. (See last month's article)

Oxygen during aging: After M/L (malo-lactic) fermentation, the wine is in a very "reduced" state. That is it is full of CO2. For polymerization to occur, you need to remove the CO2, exposing the wine to a controlled amount of O2.

This requires a "vigorous" racking and then return to barrel or carboy. It is a common French practice to rack the wine from the barrel into an open, shallow vessel, pumping the wine back into a cleaned barrel.

This allows the wine to "move forward with its life". Flavors remain bright with lean/subtle flavors/balance.

This expose is done more gently with more "delicate", less tannic, less intense fruit wines. Also rack more gently "with air" with time since oxygen hangs around longer, possibly damaging your wine.

( Caution: do not rack with air if any sugar is left.

O2 feeds biological spoilage )

A good case can be made for inoculating for M/L at crush or at least at pressing. This gets M/L over while the wine is young and sturdy, and more able to tolerate the "abuse" of vigorous racking.

So, there you have it. All that caution against air and wine may just not be the entire story. Air/O2 at the right time and in the right amount can be an helpful tool.