Do all wines benefit if you let them breathe?
No. That's true only of animals, carburetors and outhouses. In reference to wine, breathing is a colourful term for oxidation, or "degradation" in the presence of oxygen. Too much oxygen contact for too long will spoil any wine, but I placed the word degradation in quotation marks because many experts believe brief air exposure can benefit many wines by giving lift to pleasant aromatic compounds.
Just as important, breathing can help blow off unpleasant volatile substances that plague many wines, such as acetic acid (the vinegary smell), hydrogen sulphide (sewage-like odour) and sulphur dioxide (struck match).
All of this can be accomplished either by decanting into a separate vessel such as a jug or by agitating the wine in the glass through that pretentious swirling manoeuvre. Simply popping the cork and letting the wine sit for several hours in an unsealed bottle does little, I'm afraid. The surface-to-air ratio simply is negligible. Often when wine professionals want to serve an aerated wine in its original bottle, they "double decant," which is to say pour the wine into a decanter before funnelling it back into the fancy bottle, thereby achieving the requisite sloshing.
But I should stress that the benefits of breathing are a matter of debate. Some experts believe that the moment a bottle's unsealed the wine begins to decline, muting aromas from the get-go. (Pleasant smells are in the nose of the inhaler, alas, which is why the jury is out.) My impression? I believe breathing does provide one clear benefit aside from possibly enhancing aroma: It can soften the texture of an otherwise harsh young red. And this is the key reason I might sooner choose to decant young wines than old.
The main reason connoisseurs decant old wines is to separate liquid from the sediment that has precipitated out of solution over time. They leave the bottle upright for several hours to let the sediment settle at the bottom, then slowly pour into a decanter, being careful to leave the muddy, cruddy last ounce or two in the bottle.
Although it may seem counter-intuitive or contrary to popular practice, decanting old wines is in my opinion more likely to injure an old wine than a young wine. The more mature the vino, the more fragile its character. Agitate it too much or let it sit in contact with air for too long and it will end up tasting like a prune wrapped in crumbly old cigar-tobacco flakes.
The Flavour Principle by Lucy Waverman and Beppi Crosariol was recently named one of this season's Top 10 cookbooks in the United States by Publishers Weekly. Published by HarperCollins.