Article By: David Singer
Oxygen has always been a blessing and curse as it reacts to the world around it. From way back in grade school science we have been taught that oxygen is the core of the building blocks of life. Animals need it to breathe, fire to burn, without it life as we know it would not exist. On the flip side, oxygen is a main element in degradation and ageing - it is continuously combining with life's molecules and slowly destroying them, the result being oxidation. For wine, oxygen has a complex relationship starting in the vineyards all the way to post-bottling.
Old styles of winemaking are aerobic, meaning that the preventative methods of making sure oxidation was occurring were unknown or disregarded. Oxygen would be picked up during pressing, traveling from fermentation to barrel, during the clarifying process and during bottling. Because of this the fruit flavors would be diminished and the finished wine would be lacking in these notes. This is not to say that aerobic winemaking is always bad - for certain styles of sherry, vin jaune and tokaji it is part of the character of the wine. And it must be noted the oxidation is being monitored and kept under control.
Modern wine making is made via anaerobic methods, without oxygen, or at least under very controlled situations. To prevent oxygen from reaching wine today is not that difficult, it just needs good discipline in all aspects of the winemaking process. Interestingly, because of modern methods such as stainless steel tanks, some of the sulphur dioxide becomes reduced to hydrogen sulphide, giving the wine what is known as a reductive taint. For some this is a "dirty" smell. But oxygen is not the culprit in these cases. Starting after picking, the grapes are sprayed with antioxidant powder called potassium metabisulphite. This white powder is stable when dry, but removes sulphur dioxide when wet, which protects the juice during accidental breaking of the skins or after the pressing occurs.
Other modern techniques use oxygen in a beneficial method, some of which seem a little ironic, such as hyperoxidation. A common and correct belief is that wine needs to be protected from oxygen after fermentation - though some winemakers believe if the wine is protected too much, it is even more susceptible to oxidation. Ironically, if the must is allowed some contact of oxygen before fermentation, it destroys some of the more susceptible components of the juice and will result in a finished wine that is more stable. Hyperoxidation, with its use of oxygen at the correct time, still yields the fresh vibrant fruit that is typical of modern winemaking.
Another form of tempered oxygen use is micro-oxygenation. Unlike hyperoxidation, this technique is used with fully fermented wine. This is a fairly new technique that many modern winemakers have adopted. The principle is that of the slow oxidation that barrels use is applied when the wine is in tank. An extremely small amount of oxygen bubbles are added (so small that you can't see them) which results in a wine that is smoother and softer, with better integration of tannins. Michael Rolland is a big proponent of this technique.
Even after bottling, the process of oxidation continues (now that it has been proven corks are porous), allowing an extremely small amount of air in. Assuming a correct cork and seal, another factor in the rate of oxidation is the size of the bottle. The logic is cork will give the same amount of oxygen from (more or less) each bottle to bottle. As this is hopefully the only way oxygen gets in, it stands to reason a magnum will see less oxygen than a bottle, and a bottle less than a half bottle, in relationship to total wine volume.
One of the questions I am consistently asked in my classes is: "What's the best way to preserve the quality of an opened bottle until the next day or days?" Well, the best way is to finish the bottle; outside of that, in my experience, has been the use of inert gases, which for preservation units of a bottle here or there is nitrogen or argon. They can be very reasonable, about $15 a can retail. By spraying either of these gases into the bottle and then restopping with the cork, the gas rests on top of the wine preventing any further oxygen from entering the wine. Naturally there is oxygen still in the wine already because the wine has been poured, however, the process of oxidation is slowed considerably in comparison to just sticking the cork back in. The more expensive systems, some of which are installed in wine retail stores in the Boston area, do the same with even more control. This is a great way for retail clients to sample the wine before they buy at their convenience, not when the store has a wine tasting.
Oxygen is still a blessing and curse, but as time and technology proceed, its benefits are continually increased while its deficits, though damaging, are becoming less and less of an issue.