Friends tell me they prefer red wine with oak. People say that wine must spend time in oak or it won't be good. But what does oak taste like? And is it essential that red wine be aged in oak?
Oak is good for barrel storage because the wood can be bent without breaking and, when wet, expands to make watertight joints. It imparts flavours and allows small amounts of oxygen transmission so the wine can develop over time.
This sounds simple, yet for the winemaker there are lots of variables to play with.
First, where does the oak come from? French oak has a tighter grain, more wood tannins but subtler aromas, while the wider grain white American oak has fewer tannins and more pronounced aromas. Then there is the toasting, charring the inside of the barrel. It destroys wood tannin molecules but creates all kinds of aromas, from coconut and clove to dark chocolate and smoke, depending on temperature and toasting time. Wine aged in untoasted barrels has no complex aromas and its tannin is so raw it is like biting into plywood. A lightly toasted barrel gives herbs and spices, while medium toasting brings vanilla, cinnamon and smooth wood tannin. Wine aged in heavily toasted barrels acquires roasted coffee and caramelised flavours and less wood tannin. New oak imparts the most aromas and wood tannins. Barrels filled for a second and third time impart only about 50 per cent and 30 per cent as much, and those over five years old virtually none at all. But even the oldest barrel lets in that vital oxygen, softening the wine over time.
How big is the barrel? Small ones have a higher wood area to wine volume ratio so impart more flavour. Small new barrels, such as the 225-litre barriques from Bordeaux, give the most intense aromas. The time the wine spends in the barrel ranges from a few months to a few years.
Not all wines benefit from maturing in oak. A concentrated and structured cabernet sauvignon may stand up to 100 per cent new oak for 18 months, or even "200 per cent" new oak by racking the wine from one new barrel to another. But this would overpower a more subtle wine such as a Burgundian pinot noir. Some winemakers would not use new oak at all.