Wine fault: oxidation
Wine and air have a rather ambivalent relationship with one another. On the one hand, oxygen is vital for wine, for example during fermentation or maturation, and on the other, it can become wine's greatest enemy. The oxidation which then occurs is a widespread wine fault. In this article, you’ll learn how wine and oxygen react, what effects this has and how you can prevent oxidation.
The key points
- Too much oxygen leads to dull aromas and changes in colour.
- High temperatures accelerate the oxidation process.
- During the bottle ripening process, controlled oxidation is desirable.
- Wine storage fridges provide the optimum storage conditions.
Wine fault: oxidation – list of contents
Wine and oxygen: the right balance does the trick
Without an adequate supply of oxygen, the yeast cells necessary for the alcoholic fermentation of the grape must into wine cannot sufficiently grow. And without a certain amount of dissolved oxygen, the fine wine will not produce the complex aromas during its maturation for which such fine wines are so highly valued. A good winemaker therefore always strives to maintain a good balance in the ambivalent relationship between wine and oxygen – not too much and not too little.
Wine oxidises: what does this mean?
Too much oxygen in the wine leads to oxidation. This becomes evident in an increasingly musty aroma. Instead of fresh fruit, it is more reminiscent of the sliced and browned surface of an apple or of caramelised fruit. The colour usually also changes: white wines become darker, red wines tend towards a brick red colour. If the wine is still in the barrel, it's relatively easy for the winemaker to respond to the excess oxygen. A small dose of the gas sulphur dioxide (SO2) is introduced into the wine – a few milligrams are normally sufficient – and the change in taste and colour caused by oxidation disappears. The SO2 has a “reducing” effect, i.e. it removes excess oxygen from the wine and therefore effectively restores it to “zero”.
But even when the wine is finally bottled, oxygen continues to have an influence on it. This happens even when the wine has been bottled with the exclusion of oxygen and the bottles have been filled so full that there is hardly any room for air between the cork and the wine surface. This is because the oxygen already dissolved in the wine will sooner or later result in oxidation.
This slow oxidation during the bottle ripening process is certainly desirable. It is this oxidation that changes the wine very slowly, making it finer and more mature and allows new aroma components to develop. However, if this process is too fast, then oxidation is clearly a wine fault.
If a wine exhibits oxidation that is not appropriate for its age, then the deficiency may, on the one hand, be due to oxygen saturation which is too high or to insufficient protection by sulphur dioxide in the wine before bottling. On the other hand, external factors following bottling may also have an influence such as leaking closures or corks.
Protecting wine from oxidation
The storage temperature is also particularly important. High temperatures can considerably accelerate the progress of oxidation, which means oxidation can also be sign of the incorrect storage of the bottles. Wine fridges are developed specifically for optimum storage of wines. They provide a constant climate throughout the interior to ensure ideal maturing and long-term storage.
The author
Frank Kämmer
I have worked for many years in high-end restaurants and in this time became one of the top sommeliers in Europe. In 1996, I achieved the title of Master Sommelier, the highest international qualification in my profession. Today, I work primarily as a consultant in the international wine and gastronomy sector. I have also published numerous books on wines and spirits and was the first German to be accepted into the British Circle of Wine Writers.
