Why Aerate Wine? Science Behind Letting Wine Breathe

Aerating wine simply means exposing the wine to air or giving it a chance to "breathe" before drinking it. The reaction between gases in the air and wine changes the flavor of the wine. However, while some wines benefit from aeration, it either doesn't help other wines or else makes them taste downright bad. Here's a look at what happens when you aerate the wine, which wines you should allow breathing space and different aeration methods.

Chemistry of Aerating Wine

When air and wine interact, two important processes occur evaporation and oxidation. Allowing these processes to occur can improve the quality of the wine by changing its chemistry.

Evaporation is the phase transition from the liquid state to the vapor state. Volatile compounds evaporate readily in air. When you open a bottle of wine, it often smells medicinal or like rubbing alcohol from the ethanol in the wine. Aerating the wine can help disperse some of the initial odor, making the wine smell better. Letting a bit of the alcohol evaporate allows you to smell the wine, not just the alcohol. Sulfites in wine also disperse when you let the wine breathe. Sulfites are added to wine to protect it from microbes and to prevent too much oxidation, but they smell a bit like rotten eggs or burning matches, so it's not a bad idea to waft their odor away before taking that first sip.

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Oxidation is the chemical reaction between certain molecules in wine and oxygen from the air. It's the same process that causes cut apples to turn brown and iron to rust. This reaction occurs naturally during winemaking, even after it has been bottled. Compounds in wine which are susceptible to oxidation include catechins, anthocyanins, epicatechins, and other phenolic compounds. Ethanol (alcohol) can also experience oxidation, into acetaldehyde and acetic acid (the primary compound in vinegar). Some wines benefit from the changes in flavor and aroma from oxidation, as it can contribute fruity and nutty aspects. Yet, too much oxidation ruins any wine. The combination of diminished flavor, aroma, and color is called flattening. As you might guess, it's not desirable.

Which Wines Should You Let Breathe?

In general, white wines don't benefit from aeration because they don't contain the high levels of pigment molecules found in red wines. It is these pigments that change flavor in response to oxidation. The exception might be white wines that were intended to age and develop earthy flavors, but even with these wines, it's best to taste them before considering aeration, to see if it seems like the wine might benefit.

Inexpensive red wines, especially fruity wines, either don't improve in flavor from aeration or else taste worse. These wines taste the best right after they are opened. In fact, oxidation may make them taste flat after half an hour and bad after an hour! If an inexpensive red smells strongly of alcohol immediately upon opening, one simple option is to pour the wine and allow a few minutes for the odor to dissipate.

Earthy-flavored red wines, especially those which have been aged in a cellar, are the ones most likely to benefit from aeration. These wines may be considered "closed" right after they are uncorked and "open up" to display a greater range and depth of flavors after they breathe.

How To Aerate Wine

If you uncork a bottle of wine, there is very little interaction through the narrow neck of the bottle and the liquid inside. You could allow 30 minutes to an hour for the wine to breathe on its own, but aeration greatly speeds the process so you don't have to wait to drink the wine. Taste a wine before aerating it and then decide whether or not to proceed.

• The easiest way to aerate wine is to attach an aerator to the wine bottle. This aerates the wine as you pour it into the glass. All aerators are not the same, so don't expect the same level of oxygen infusion from each type available on the market.
• You could pour the wine into a decanter. A decanter is a large container that can hold the entire bottle of wine. Most have a small neck, to allow easy pouring, a large surface area, to permit mixing with air, and a curved shape to prevent wine sediment from getting into the glass.
• If you don't have an aerator or a decanter, you can pour the wine back and forth between two containers or simply swirl the wine in your glass before drinking it. There's also a practice called hyper-decanting, which involves pulsing wine in a blender to aerate it.