decanting? (wine newbie)
What is purpose of decanting, versus just letting wine sit in the glass to expose to oxygen? Wikipedia says
"...oenologist Émile Peynaud claiming that the prolonged exposure to oxygen actually diffuses and dissipates more aroma compounds than it stimulates, in contrast to the effects of the smaller scale exposure and immediate release that swirling the wine in a drinker's glass has. In addition it has been reported that the process of decanting over a period of a few hours does not have the effect of softening tannins"
There are two main reasons for "decanting" a wine.
#1 - separating the wine from any sediment
#2 - introducing oxygen to the wine - often referred to as "caraffing" the wine, and most often applied to a big, young white wine.
The operations are very similar, but with different purposes.
Which wines are you inquiring about, specifically?
I find that many recs. to decant, are not always the best. If aeration is the required element, then one should monitor any change in the wine, fairly carefully. I see very broad instructions, such as "always decant for X hours... " and take those with many grains of salt. I monitor, and will declare, based on MY palate, when it's time to serve.
Decanting can serve a couple purposes. First is the ability to separate out physical sediment from the wine itself. If you are a fan of vintage ports, you know how much sediment can be encountered which would detract from enjoyment of that wine. In general bigger style reds have the ability to generate sediment as they age.
Second benefits involve the 'breathing' aspect where the aromatic qualities bloom with exposure to air. This benefit seems most apparent in larger style reds and whites simply by allowing aromatic compounds to be released into the air.....this can happen both by decanting and pouring/swirling into a glass.
A third benefit of decanting affects the flavors of a wine to 'open' and become more pronounced. This may prove the most difficult to discern since the flavors of a wine from the point of opening to drinking does not always change noticeably.
Some bottles, perhaps younger ones, seem to have a set of fresh flavors that are consistent for a couple hours before they begin to degrade.
Other wines, often with grape blends, benefit from aeration by enhancing a bloom of flavor components allowing different nuances (real and imagined) to be discerned.
Finally there are wines that when first opened are simply 'dumb' or 'closed' upon opening and which benefit from aeration (and often a bit of time) to 'open' and reveal its aromatics and flavors. Rarely would this transition be apparent in thin or simple wines but I've experienced it numerous times with big complex wines like a Chateauneuf or Barolo when the evolution flavor intensity at opening/decanting to what it is a few hours later is a night and day contrast. One memory was opening an 89 Chave Hermitage that started out so close to flavorless that it was scary (hoping to serve for a special dinner) but tasting it hourly revealed a wine that substantially benefited from a lot of air and time to reveal itself.
Not all wines benefit noticeably from decanting and aeration and some wines, particularly very aged ones, may suffer by allowing their reduced aromatics to dissipate in a matter of minutes and shorten your enjoyment of the wine. Decanting and aeration is not a 'one size fits all' process and its timing is also a variable that warrants consideration, particularly with cellared wines.
I can't give you the precise chemistry behind it, but in general where beneficial, de-canting tends to "open up" the full flavor profile of the wine AND dissipate some funky flavor notes the wine may have acquired.
Decanting (pouring from a draft spigot or hard-pours from bottle to glass) has the same effect on great beers btw.... you're not going to get anywhere near the same range of flavors if you don't aerate the product.