When to decant
Why does wine need to be oxygenated?
The main purpose of decanting a bottle of wine is to open it and make it unfold so that the aromas and flavour become more complex and harmonious. Another purpose is to leave any sediment behind.
What types of wine should I decant?
(Some) Cheap wines
It can make a lot of sense to decant cheap wines because it often improves their flavour. Cheap wines sometimes have a rotten egg aroma due to sulphur dioxide. Most of us are very sensitive to this smell and it can ruin our wine experience. Luckily, a good decanting can get rid of that awful smell and make the wine taste significantly better. Watch out, though, as some cheap wines are already oxidised from light exposure, bad packaging, or simply bad produce. Decanting oxidised wines will naturally make them deteriorate even more.
Decant quality red wines, such as Italian wines like Barolo, Amarone, Chianti, Montepulciano d’Abuzzo, super-Tuscans etc. Other good candidates are Syrah, Malbec, Petite Sirah etc. The wines will open and any sediment will remain in the decanter. However, if the wines are very old or have been stored in a light/warm place for a long period the wines may already be quite oxidised. Taste a little of the wine and consider if you think the wine can handle the extra oxygen.
Personal preference whites
Some people prefer their big Rieslings or White Burgundies decanted, as they will open up faster than if you just swing them around the glass. Same goes for whites that have been aged in wooden barrels as decanting can make these wines more harmonious and remove any sediment or crystal that may have evolved during the ageing.
When you take the bottle from the cellar or shelf where it has been resting on its side, simply stand it upright for 5 - 10 minutes if the bottle is less than 40 years old. The sediment in Port is quite heavy and will settle down quickly. If the wine is 40+ years you should let it stand upright for about an hour.
The purpose of decanting old vintage port is to get rid of the sediment. Decanting is easiest with good light behind the bottle, which enable you to see the sediment clearly when it reaches the bottle neck. If you are concerned that you may not be able to see the sediment when it reaches the bottle neck, you may wish to use a funnel with a filter or thin cloth to catch the sediment as you reach the end of the bottle. Do not use paper coffee filters as they can enfuse off flavours into the wine.
With young wines up to 40 years of age the oxygen exposure works to open the powerful and concentrated character of the wine.
With older wines you should only decant 30 minutes to an hour before drinking. At this age, the wines have moved on from their youthful density and power, to more delicate and nuanced elegance, and hence the need to “open up” the wine with exposure to oxygen is no longer present.