What is "decanting" and why people do that?

DECANTING WINE

Fundamentally, decanting serves two purposes: to separate a wine from any sediment that may have formed and to aerate a wine in the hope that its aromas and flavors will be more vibrant upon serving.

Older red wines and Vintage Ports naturally produce sediment as they age (white wines rarely do); the color pigments and tannins bond together and fall out of solution. 

Stirring up the sediment when pouring will cloud a wine’s appearance and can impart bitter flavors and a gritty texture. It’s not harmful, but definitely less enjoyable.

Decanting is simply the process of separating this sediment from the clear wine. It’s fairly safe to assume that a red will have accumulated sediment after five to 10 years in the bottle, even if this can’t be verified visually, and should be decanted.

Sediment is a desirable by-product, especially in age-worthy red wines. However, sediment can have a rather bitter flavor, gritty texture and unattractive residue, so decanting (or separating) the wine from a sediment is a step worth taking. 

If the wine you are planning to serve has sediment, it should be left standing upright for 12 to 24 hours to allow the sediment to settle at the bottom of the bottle. At this point the bottle is carefully uncorked and wine gently poured into a decanter in a smooth, uninterrupted motion. Place a light under the neck of the bottle as you are pouring into a decanter so that you may see when the sediment of the wine is approaching the neck. The idea is to leave a sediment in the bottle and serve clear wine from a decanter.

WHAT WINES SHOULD BE DECANTED

Cheap wines

Decanting any cheap wines because it makes them taste better. Cheap wines can have really awkward rotten egg smell sometimes when you first open them due to sulfide dioxide. Our noses are very sensitive to this smell (some more than others) and it can ruin a wine tasting experience. Fortunately, often this smell can burn off very quickly after decanting wine and the resulting value wine can be very tasty!

Expensive vintage wines

Decanting expensive vintage wines, especially massive cabernet sauvignons, Italian wines such as Barolo, Chianti, Montepulciano d’Abuzzo, other grapes such as  Syrah, Malbec, Petite Sirah, Cabernet Sauvignon and Merlot.

ALLOWING WINE TO BREATHE

Allowing wine to “breathe” is simply a process of exposing it to air for a period of time before serving. Exposing wine to air for a short time can help soften flavors and release aromas in a way similar to swirling the wine in your glass. Young red wines, especially those that a high in tannins, such as Cabernet Sauvignon, most red Zinfandel, Bordeaux and many wines from Rhone Valley, actually taste better with aeration because their tannins soften and the wine becomes less harsh.

Uncorking a bottle and letting it sit undisturbed for period of time actually does very little to let the wine breathe as only a small percentage of wine is in contact with air. A much better suggestion is aerating the wine in young glass or in a decanter.