Wine decanters are a funny thing: They're cool to look at, but they take up major shelf space. They're a nice addition to a formal dining table, but afterwards they're hard to clean. A lot of couples put one on their wedding resgistry, but friends who've only seen them chug $6 bottles from Trader Joe's are perplexed as to why it's there. What are wine decanters for anyway?
When you've got a bottle of wine with 15+ years of age, it's common to find that tannins and other particles have seperated out over the years, forming something we'll call sediment but more common imbibers might call "gunk." The stuff is harmless, but it's not something you want in your mouth because it's gritty and it doesn't taste good. You'll want to slowly and carefully pour (or, shall we say, decant) such a wine from the bottle to a decanter to seperate wine from sediment. This video shows you exactly how a sommelier would decant a mature wine, step by step.
I don't typically drink older wines at home, but I do bust out my decanter often for a different purpose: aerating. About 20-30 minutes of airing out will help most wines open up, releasing more aroma and thus enhancing flavor, and many hearty reds flat out demand at least that much before they reveal their best side. Only sparkling, very aromatic, or delicate aged wines won't benefit from a little air. Contrary to what many a casual drinker might tell you, simply opening up a bottle of wine doesn't "let it breathe" very much. To get your wine really huffing and puffing oxygen, you need to expose as much surface area as possible, hence the wide, shallow base of a well-designed decanter. I never bother with the decanter for everyday whites or light reds, but for a big red or a high quality wine it's well worth it.
"On the Bottle" is a column about wine and spirits appearing every Friday on the Martha Stewart Living Radio blog. Email your boozy questions and wine quandries to firstname.lastname@example.org and they'll be answered in a future post.