Oh, oh, oh, O2

For years my debates over wine have mostly taken place at the august levels of academia, or at least with wine pros. Now that I am the world's most over qualified wine guide most of my skills of rhetoric are aimed at consumers.

I like to think of myself as a scientist. I don't actually get to work in the winery's lab, but every time I walk pass it I look at all the bubbling concoctions in the glass apparatus and think to myself how cool it all looks. Chances are it would look less like fun if I actually had to do all of that hard work, but from outside looking in, it is fascinating.

So, not a chemist or even a lab rat, but a scientist none the less. I regularly test assumptions, and wield reason like a sword. My debunking has ruffled more than a few feathers on this blog, and in other journals as well. Now I take my aim at a most controversial subject.

That the roll of oxygen in the aging process of wine is even controversial surprises me. My great hero, the late Emile Peynaud spent decades experimenting with wine and he stated unequivocally that wine ages without the presence of oxygen, and that a hermetic seals is most desirable.

Since I extoll the virtues of experimentation over the pronouncement of experts I certainly do not fault those that wish to prove the veracity of the roll of oxygen. I think somewhat less of those who just take it for granted that oxygen is required for wine to age.

The debate often hinges around screw caps and corks. There are those who state that a small amount of oxygen travels through the cork and helps wine age. Screw caps being perfect hermetic seals do not allow this passage of O2 and therefore are not well suited to aging wine.

Those in the O2 camp will go so far as to suggest that gas permeable membranes should be used in screw caps to allow for better aging and to lessen the chance for the wine to develop reductive odors (more on that soon).

For those that know, or want to know, a whole lot more about the chemistry involved, start with one of the most important aspect, the redox potential.

Reductive odors in a practical sense are nasty rubber smelling off odors that hopefully you will never experience in wine. If you ever come across a wine that smells like that try putting a piece of copper (a penny will work) into the wine. If the smell goes away the odors were indeed the result of reduction. If not it was another similar off odor.

Since the copper trick works even before bottling, there is no excuse for a winery to release a wine with that has this fault. In all my years I have only come across it a few times.

One of the ways a winery can ensure that the wine doesn't smell like a shower cap is to give it plenty of oxygen during the wine making process. For wines aged in barrel the small amount of gas that passes through the wood, combined with careful racking (moving to new barrels) is usually enough. For wines that don't see wood, it is not uncommon to let the wine splash about before bottling.

If a winemaker is complaining about reductive odors in their wine, it may be more a matter of winemaking that is to blame than the hermetic seal of a screw top.

As is my want, I have taken a long winded approach to get to the point I wanted to make. I am about to apply a bit of logic to the argument about oxygen and wine aging.

Oxygen turns wine brown (just like the bite out of an apple turns brown).

To say that oxygen is required for aging wine is to say that an aged wine should be brown.

A brown wine is not considered good by any measure, therefore oxygen is not beneficial to the aging process.

I would expect someone to point out that it is a question of degrees, and that some oxygen may be beneficial while too much is not. To them I would reply, how much exactly, and how do you ensure that said amount and no more or less is introduced to the wine?

I usually toss around big words like esterification when talking about wine aging (the reaction of alcohol and acids) but I honestly don't know about the roll of oxygen in the process one way or another. No doubt it will come up in the debate.

I really want to hear from others more learned on the subject, although few have deigned or dared to debate me on this forum, but I always welcome it.

Screw caps are a good thing because they keep air, including oxygen out. I have yet to be convinced that any seal less than hermetic is as good or even better.