The Oak Yoke – the Top 10 Facts about Oak in Wine

Do you like oaked wine?  Do you just slip it into your trolley at the supermarket, and hope that no-one sees it?  Or do you buy it from your local wine merchant and ask them to wrap it in a brown paper bag to hide your shame?

Oaked wines are still pretty unfashionable in the main, though perhaps judicious use of oak is becoming acceptable again as the race for clean, ever-cooler climate wines comes back from the edge.

Fashion aside, what are the different variables in play when it comes to oak in wine? There are lot of them as it turns out, so let’s have a look:

1. Format

Oak flavours in wine come from different levels of “naturalness”.  Oak was first used because of its suitability as a storage vessel – we’re talking barrels here.  Barrels come in lots of different sizes (see below) and are quite expensive.

The next level down, and significantly cheaper, is to use a few oak staves – just chuck them into the wine as it ferments or matures.  Apparently, this is what gives Diemersfontein’s “Coffee & Chocolate” Pinotage it’s funky flavours.

Diemersfontein Pinotage
Diemersfontein Pinotage

Cheaper still is the use of oak chips, sometimes in a permeable bag. This teabagging (steady at the back there!) can often result in bitter flavours leaching out of the wood into the wine.

The final, least natural and authentic method is to use oak powder.  This really is scrapping the barrel (erm sorry) in terms of quality, but if you’re buying the cheapest bottle on the shelf this is probably all that the producer could afford.

So now we know the importance of the format, we can assume that it’s barrels we’re talking about…

2. Age

In general as barrels get older they impart less flavour to the wine they hold.   Some winemakers like the impact of new oak, particularly if there is a lot of fruit and tannin (for whites) to match. Others prefer the micro-oxygenation that oak barrels can bring, but don’t want the flavour to dominate, so they use older barrels.  For example, Steve Webber of De Bortoli Yarra Valley uses new oak barrels on his standard wines so they are “seasoned” to be reused on his premium wines.

White wine producers in cool climates have another factor in play.  When the temperature of their wines drops during winter translucent tartrate crystals precipitate out of the wine.  Over several years of use these harmless crystals build up as a lining on the vessel and prevent any contact between the wine and the actual wood.

For the most expensive “Icon” wines, it is not unknown for 200% new oak to be used – that is, the wine spends a year in new oak and then it is racked off into an entirely new set of barrels for another year.  Doesn’t make for easy drinking on release, but does make for a long life.

3. Size

A rule of thumb is that smaller barrels have a more marked impact as the ratio of volume to surface area is lower.  The standard barrel of Bordeaux is the 225L (300 bottle) barrique, and this has become the default.  Burgundy’s tradition encourages the use of the slightly larger 228L pièce or 300L Hogsheads; these are more common where a producer is trying to create something akin to Burgundian Chardonnay.

Barriques in the barrel hall of Château Mouton Rothschild
Barriques in the barrel hall of Château Mouton Rothschild

Port was traditionally shipped in a pipe – a pipe of Port was a traditional gift bought for a (presumably well-to-do) child around the time of their birth so that it would be ready for drinking upon their majority.

In some parts of Europe, much larger formats are used, particularly for aromatic whites where oak flavours are considered undesirable.  In Alsace the term foudre is used (usually with an oval end) whereas the Italians are proud of their botti.

Alsace Foudre
Alsace Foudre

4. Timing

There are two distinct stages in the wine-making process where oak can be used, fermentation and maturation.  Makers can use oak during either, neither or both, all down to their preferences.

5. Time

This is a biggie – the longer wine stays in oak, the more of its flavour it will take on.   In Rioja, for example, the length of time in oak is enshrined in the quality classification, though of course the age of the wood is not specified.

6. Proportion

Another way that producers temper the use of oak is by only putting a certain proportion of their wine into oak for maturation – the remainder usually being in stainless steel or concrete vats.  All the vessels’ contents are blended at the end so that the resulting wine is moderately oaky.

7. Geographic Origin

Oak from different places gives different flavours and allows different levels of oxygen to get to the wine.  The main sources are below.

French oak is generally regarded as the gold standard, and is often the most expensive – mainly down to the fact that staves have to be split out manually with the grain rather than sawn into shape.  Within France there are several areas with oak forests used for wine barrels, with Limousin, Tronçais and Nevers the most renowned.  French oak often gives subtle, smoky flavours.

American oak can be sawn across the grain and still remain watertight, and hence is cheaper to use in barrels.  It is a different species from European oak (there are actually hundreds of different species, of which only a few are suitable for barrels.  American oak is traditionally used in Rioja and other regions of Spain as well as in the USA.  It gives smooth vanilla tones.

Slavonian oak is confusingly from Croatia rather than Slovenia which it sounds so much like.  It has long been the oak of choice in Italy, and tends to be hand sawn which allows lots of tannin to leech out into the wine; Sangiovese and Nebbiolo can handle the tannin but larger formats help.

Portuguese cork trees are a species of oak, but obviously have a different role to play.  The oak more suitable for barrel making is grown in the greener north and is cheaper than the more prestigious French sources.

8. Toast

Once the staves have been seasoned by drying in the open air or a kiln, they are ready to be assembled into a barrel.  Part of that process is the toasting, or charring of the inside over an open fire.  The amount of toasting has a significant impact on the wine which is then put into it – both on the aromas and flavours.

9. Cooper

Now this is the really geeky bit – some wine producers are so particular that they will even specify a particular cooper (barrel maker) as well as the source of the wood and the toasting it receives.

10. Other woods

So after all that, are there any other woods which get used instead of oak?  Yes: chestnut, cherrywood, pine, acacia and even redwood have been used.  The vintners of the Veneto sometimes use cherry to accentuate the cherry flavours in their wine.  Some of the other woods are used for cost reasons, and because they impart undesirable flavours they are coated inside before use.