Decanting — the transfer of wine from the original bottle to a separate serving vessel before drinking — is an under-appreciated and often overlooked task for the wine lover. The process serves two important purposes — to expose the surface of the wine to oxygen and to filter out any sediment in the bottle.
First, since a wine bottle is virtually oxygen-free, the sudden expansion of the liquid into a decanter exposes it to the open air, inducing evaporation and oxidation which, in turn, trigger the release of chemical compounds relating to alcohol and aromatics. This can also "blow off" any burnt- matchstick or rubbing-alcohol smells that may have built up inside the bottle. The result is wines that exhibit more fruit character, complexity and roundness, and less tannic stringency.
Second, as wines age, or in unfiltered wines, sediment precipitates out and collects in the bottle over time. While this is safe to consume, the wine will be cloudy and can taste gritty and bitter. To remove sediment, let the bottle sit upright undisturbed for at least 30 minutes to allow the precipitate to sink to the bottom, Then, holding the bottle horizontally, slowly and carefully pour the contents into a tall decanter, stopping when a bit of sediment can be seen mixing into the liquid. The remaining sediment can then be discarded.
Decanting can be accomplished using any open-mouthed container, from a Mason jar or pitcher to an elegant cut-crystal specialty decanter. Some advocates endorse "double decanting," in which wine is first poured into a decanter, then transferred back into the cleaned bottle, thus oxygenating it twice. A bit more aggressive means involves using specialized aerating devices that force air into wine. The most aggressive of all is "hyper-decanting" — churnin wine in a blender or vigorously shaking the bottle.
Young and highly tannic reds like Cabernet and Syrah will benefit most from decanting, requiring up to two hours of exposure, while those older than 20 years can lose flavor and aroma compounds much more quickly. Lighter reds like Pinot Noir can be left for 30 minutes while bolder whites like Chardonnay can stand up to one hour. These are not hard and fast rules and wines need to be sampled during the process to ensure quality
Oenology 102: The Basics of All Things Wine
Oxygen is both the enemy and ally of wine. Too little exposure to oxygen (reduction) can result in unpleasant odors like burnt matches, muskiness, or rotten eggs, while too much exposure (oxidation) will turn wine a brownish color and rob it of its fruitiness and aromas, ultimately transforming it into vinegar. The ideal is a balanced level of the two.
When a wine’s flavors and aromas are muted or the wine is too tannic or acidic, wine tasters refer to it as "closed" or "tight." The wine needs exposure to air to give it time to "open up" or "breathe" in order to soften flavors and maximize aromas. This is accomplished by decanting or by swirling in the glass.
Sediments in wine (dregs) are composed of dead yeast cells, the remains of grape solids, and tartrates (tartaric acid crystals). While these substances are natural and safe to consume, they can be gritty and bitter in the mouth.
Natural wines are bottled unfiltered, but the majority of wines are sold filtered. Still, sediment will precipitate out as a wine ages.