Fermenting and maturing a well-made wine in oak barrels softens the wine, and makes it more complex.
Four things happen when a wine sits in an oak barrel:-
- Chemicals are leached out of the wood, which provides the distinctive vanilla taste, amongst others.
- Small amounts of air pass through the barrels, which influences the way the wine matures.
- Some wine is absorbed into the barrel, and some alcohol evaporates. So the wine in the barrel needs to be topped up.
- The wine is gently clarified.
Types of oak and their treatment
Several different types of oak are used, and each gives a different taste. The oak is split into strips, known as ‘staves’, and allowed to dry outside. This seasoning removes the harsher tannins in the wood. The barrels can be further treated by burning the inside, a process known as toasting, which also reduces the flavour and tannins which are imparted to the wine. This video by Jordan Winery tells you all you need to know.
New barrels vs old
Old barrels, which have been used before, will impart less taste than new barrels, as most of the chemicals have already been leached out.
Large barrels vs small
Large barrels impart less taste than small ones, because the flavour is diluted over a larger volume. Also, the air that penetrates the barrels is spread more thinly in large barrels, which leads to slower ageing.
Some winemakers put oak chips into their wine while it is maturing, to give it ‘oak character’. This is obviously cheaper than using oak barrels, and is used on cheaper wine, sometimes with unfortunate results.
Where it can go wrong
The use of oak in winemaking is a complicated business, and a great deal of skill is required in dealing with it. Several factors are listed above, but there are more besides. Most importantly, the wine needs to be tasted during its evolution. Not all wines improve with exposure to oak, and it is easily overdone.