Why Does Wine Need to Breathe?

You've been poured a glass of wine over dinner. Lifting the wine glass to your lips, you are admonished to let the wine breathe while you wonder why wine needs to inhale or exhale as if it were a living thing.

Wine needs to breathe more for the chemistry going on than the biology of its plant origins. Lest we lose you at the mention of chemistry, let me describe it in the vocabulary of the wine connoisseur.

Breathing allows a wine to warm up, to mellow out, to open up, to soften. It deepens the flavors, enriches the aromas, improves the characteristics, makes for more malleable tannins, and produces mild oxidation. Okay, we can't get away from the chemistry. In simple non-technical parlance, breathing makes a better wine experience for the imbiber.

But, it's because of the chemistry, the mild oxidation of tannins that is, that makes for that better wine imbibing experience. What are tannins and why are they in wine? Here's where chemistry and biology come together.

Tannins are polyphenols or large organic molecules. They occur in the skins, stems, and seeds of grapes-particularly the red ones--and get into the liquid when these parts of the grape plant are crushed to make wine. Secondary sources of tannins in wine are the wood barrels in which wine is aged as well as the cork in the bottle.

Tannins are astringents, imparting that dry, puckering, bitter taste to wines upon opening. During aging, however, tannins in the wine are what prevent oxidation as the wine matures. While wine ferments for months or years in the barrel, oxidation takes place through the pores of the wood but slowly, owing in part to the presence of tannins. That is a good thing, as oxidation at faster rates would ruin the wine while it was still grape juice.

So now, you've opened your wine, took a sip, and puckered your lips in a bitter grimace. You've consumed the tannins, those astringent molecules natural to grapes. Although tannins decompose with the slight oxidation that happened during aging in the barrel, there's nothing like letting oxidation proceed freely for awhile upon opening the bottle.

Tannins decompose rapidly from oxidation upon exposure to air. Letting the bottle sit, however, exposes too little surface area. Faster oxidation is accomplished by decanting the wine, pouring it into a glass, or aerating with a device called a Vinturi. All achieve just enough oxidation to reduce the tannin content for pleasurable drinking but not enough to ruin the wine right then and there.

An open bottle of wine goes bad in time, although that time period varies widely. Experimentation and experience are the only ways to determine whether a wine is ready for drinking with enough reduction in tannins yet oxidation incomplete enough to avoid ruin.

Let the chemistry begin. Like you, wine needs to breathe to reach its fullest potential. After that, it's bottoms up!