This is one question I’m often asked, and the answer is not that simple. To begin with, there are actually two different processes that may be confused; decanting and aeration.
Is the process of carefully pouring clear wine out of the bottle while leaving any sediment or deposits behind. It is usually required when you’re drinking older, or minimally fined and filtered wines. Without getting too technical, wine is much more than a mere liquid with a bunch of stuff dissolved in it. It is a matrix with all sorts of things floating around, some dissolved, some in suspension and in between. Colour, tannin, acid and alcohol are major parts, then there are many minor compounds which make up this complex mixture. Generally as wine gets older, some of these compound become less stable and fall out of suspension. These end up on the bottom of the bottle as either a fine sludge or gritty crystals. It’s not very pleasant to drink, especially if you end up with the last glass and it’s all in there! So by removing it before you serve the wine you save yourself or your guest a mouthful of gritty mud.
Here’s what to do. Stand the bottle upright for a few hours if it was lying down. Carefully handle the bottle when you are opening it so you don’t stir the sediment up. Find a suitable receptacle for the wine (either a $1000 Riedel decanter or $5 IKEA water jug will do fine). In one smooth slow motion, pour the wine into the decanter or jug. When you get near the end, slow down further and watch the wine as it comes out, watching for sediment. A little is fine. Leave the rest in the bottle. If you like, rinse the bottle out and pour the wine back in to serve. Job done.
Choosing whether or not to aerate a wine requires a little more understanding. Splashing the wine into a decanter or jug, or through an aeration device will add oxygen to the wine. This can do many things such as ‘blow off’ excessive Sulpher Dioxide or some Sulphide characters. Extended time after the initial aeration may begin to soften the tannins in the wine. The air also lifts the aromas in the wine and this is usually the reason to do it. Really young red wines (1-4 years old) may benefit most. The Sulpher is high, there may be some fermentation Sulphides present and there’s usually a lot of young grippy tannin. So splash away. After a few minutes you’ll often see a marked improvement in the generall drinkability of the wine.
If you’re going to open an older wine though, you need to start thinking a little differently. Especially if the bottle has been sealed with a cork. A very slow, natural aeration process happens over the life of the wine, through the cork. So a maturing red wine, say 12 years plus, may not require aeration at all. Here you would open the wine, maybe decant (if you do, then carefully without splashing), then pour some into a glass and let it gradually open up itself. This way you can look at the wine as it is opening up and see the changes as they occur. If you actively aerate very old wines (20+ years) you run the risk of missing the wine at its best.
To sum it up
As with anything to do with wine, storage conditions will have a large affect on how the wine matures. Putting this to one side though, generally I’d say less is best. Better to under aerate than over do it and oxidise your wine. Be gentle with old wine and let them slowly reveal themselves. But if you’re grabbing a young ‘big’ red to have with dinner then a good aeration should really help it.
Finally, I have one little tip to help you decide whether or not to buy more of a particular wine. If you opened your young red and didn’t finish it on the first night, try it again the next night. If it drinks better than when you first opened it, then it should improve with time in the cellar.
Winemaker, Rusty Mutt Wines.