The popping sound of the cork and the small release of air from a bottle is a method of aeration, more colloquially said as allowing a wine to breathe.
Aerating wine is the exposure of wine to oxygen, which can be done through as little as opening a bottle and letting it sit, thorough decanting or a few swirls of a glass in the hand. For trained wine testers, letting a wine breathe in any of these contexts can make the difference between a closed or more open wine. Aeration serves as a catalyst for the oxidation process.
The Science of Oxidation
Oxidation is the chemical process in which the ethanol in wine is converted to acetaldehyde after exposure to oxygen. It is often said that oxidation starts at the vineyard and does not stop until it is sipped from the glass, as it is impossible to keep oxygen entirely separate from wine.
Controlled oxidation is done using various methods, which can alter resulting notes and flavors in a wine to the winemakers liking. Open-tank fermentation is exactly what it sounds like; fermentation of the wine takes place in an open-top container, which allows for oxygen to increase the population of yeast involved in the fermentation process. Oxidative aging—most commonly known for making Sherry — involves enough controlled exposure to oxygen to impart nutty or fruity flavors to wine.
The opposite of oxidation is known as reduction. Wines are made through this process as well. Rather than the wine being exposed to oxygen, it is exposed to carbon dioxide in the reductive process; any contact with oxygen is blocked. Reductive wines are much more sensitive to the oxidation process when opened and exposed to oxygen, resulting in more drastic changes to the taste of the wine.
While oxidation is recognized as a part of winemaking, it can have some pretty detrimental effects. Like browning banana skins and decaying apple slices, oxidation causes wine to spoil if uncontrolled. The results of oxidation will serve as cue to the wine drinker that the wine is past its prime. From losing all fruity aromas and nuanced notes, the wine will taste flat. Beyond that, a completely oxidized wine might develop a vinegar-like taste accompanied by a metallic odor.
Different Avenues to Aerate Wine
After a wine has been sitting on the shelf for weeks or months, it could benefit from a bit of stirring up. Opening a bottle is usually not enough to experience the full effects of aeration, which can alter different tastes that shine through. Wine lovers who dedicate counter space to a decanter and continuously swirl a glass are not only doing so for show.
Decanting wine often yields the best results in regard to the quickest avenue of aeration. A decanter is any vessel that holds wine in order for air to make contact. Although any large container can function as a wine decanter, most found in the kitchen of a wine enthusiast resemble a glass or crystal vase with a slim neck and wide bottom. Only decant wine if the expectation is that it will be gone the same night. After being processed through a decanter and fully aerated, the wine begins a shelf life. Decanted wine should be enjoyed within two to three days.
Swirling a glass can tell a lot about a wine for an experienced wine drinker. It shows the denseness of a wine by its level of attachment to the sides of the glass. It reveals a sparkling wine through the emergence of carbonation when disturbed. It extracts any aromas that sit on the surface of the wine for a proper tasting experience. The advantage that comes with merely swirling a glass is that the rest of the bottle is able to sit more or less undisturbed. Therefore, the wine will not suffer effects as severe if the plan is to store for future drinking.
Tasting A World Of A Difference
Why all the fuss over aeration? Wine enthusiasts will describe wine as closed if the acidity or tannin is overpowering other flavors, hindering the taste. Exposing the wine to oxygen will bring out the more subtle notes. The process could take up to an hour before the flavor undergoes noticeable changes.
Especially for a young wine with high tannin, a quick pop and pour from the bottle might not allow enough oxygen in for certain wines to reach peak flavor. Aerating can help to lessen any tannic flavors and soften harsh qualities to be less austere. A bit of oxygen can also allow aromas to be extracted to sit on the surface of the wine for proper tasting. However, aeration could take longer than usual when dealing with these flavors.
Not all wines need to breathe. Aged wines, like Burgundy, are commonly very fragile and should usually not be aerated. However, bottle-aged wine can come with a sediment that is unfavorable to have land in a glass that folks often choose to separate out through a decanter. It is important to do this slowly to expose the minimal surface of the wine to oxygen.
Look to the typical serving glasses for a hint on whether or not a wine needs to be aerated. Wines served in wide, globe-shaped glasses are encouraged to be swirled a bit. Champagne is often served filled nearly to the top in a skinny, tall glass called a flute. The average pour for champagne is roughly five ounces, the same as any other wine. Less room for movement in the glass tells you that champagne could do without a swirl from the wrist. Oddly, it has become increasingly popular to decant sparkling wine, which can cause the wine to lose its bubbles.
Rely on preference. Many believe that decanters are strictly for red wines, but that is not necessarily true. Try your favorite white wine before running a sample size through the decanter and let yourself be the judge. The important thing is that you find the wine that you drink to be accessible. Cheers!