What is: Oak Ageing?
Lock, Stock & Barrel...
Is there anything nicer in the World than the warm gentle feeling given by the nose of an oak-aged wine, almost like a hug? Somehow mystical, the notes of vanilla, spices and great Noble oak seem to talk straight to our soul, moving us to a place of harmony & relaxation. Why oak? Which type of oak? How long should we age the wine for? There are plenty of questions that come to mind once you realise the potential of this wonderful tree on flavours and textures. I am going to try to respond to a few of these questions and explain the magic behind oak.
Why Did we Pick that Tree?
Through History, a few different species of trees have been turned into barrels, some regions of the world still use the likes of black locust tree for its floral aromas, cedarwood in the ageing of some stouts or even chestnut wood and others. However, oak is the most widely used timber in the wine industry because of its flavour profile and its tight porousity to oxygen.
The Science Behind Oak
The following information might break the magic about oak ageing but yes, it can all be explained by science. Oak wood contains various levels of tannins (known as polyphenols), but also aromas carried by their lactones and other phenols and a variable porousity to oxygen. For instance, the aroma of vanilla often found in oak-aged wines comes from a compound called Vanilline, some phenols are also responsible for clove aromas (that’s eugenol) or the lovely 4-ethyl-gaiacol and its peppery and spicy notes.
French & American Oak
As you might have read already on the back labels of some wine bottles, we usually talk about French or American oak. Not just a difference of origin, these two are completely different species. French oak actually refers to two species itself, known as Quercus Petraea and Quercus Robur. The first, Quercus Petraea, or sessile oak, is widely used in the wine industry for its ability to turn harsh wine tannins into a smooth mouthfeel, and its long-lasting aromas of nutmeg, clove or even cinnamon. On the other hand, Quercus Robur, also known as Pedunculate oak, is very rich in tannins and is mostly used for ageing spirits.
American oak, known as Quercus Alba, has a lower tannin content than its European counterparts, but a much bigger aromatic profile. It is easy to spot for its notes of vanilla, mocha, chocolate, coconut or dill.
Another big difference is that aromas from French oak usually take more time to kick off on the palate, the first feeling given is usually the smooth texture of the wine, but then it builds up a very long-lasting finish full of dry spices such as cloves, nutmeg and cinnamon. Whereas American oak is more like a punch in the face, an explosion of rich aromas from the start, with strong notes of vanilla, chocolate or coconut, but with a shorter length on the palate.
So why would we use one oak or the other? In the past, geography was the reason and winemakers were using the oak from their regions. But today, we can import any type of oak anywhere, so the reason for choosing one over the other is a matter of taste and desired wine style. American oak can add the kick that is often missing from very ripe grapes in Hot climate areas, a big opening followed by the jammy fruitiness. French oak, on the other hand, will melt the harsh tannins of grapes that have lacked a bit of sunlight and heat, and will give a smoother mouthfeel to big reds from cooler climates. Also, the use of American oak will often result in lovely wines for drinking on their own, wines that give all of their aromas quickly and don’t last too long without food. French oak will probably produce more food friendly wines that leave all the space to the aromas in your plate first and then carry them and enhance them for a long while afterwards.
"American oak gives notes of vanilla, mocha, chocolate, coconut or dill. French oak gives a dry spiciness with nutmeg, cloves & cinnamon"
A Different Cut...
While it is true that American oak naturally imparts higher aromas to the wine, this is often increased by the way the staves are cut. In Europe, coopers would traditionally cut the staves along the grains of the wood, resulting in a long natural drying period of 2 to 3 years to obtain a water-tight barrel that is permeable to oxygen. However, it is more common in the New World to cut the staves across the grains of the wood, resulting in a bigger transmission of aromas into the wine and allowing a shorter mechanical drying period of about a month only.
Butt, Hogshead & Blood Tub…
If the word “barrel” is commonly used, it should only refer to one size of cask of approximately 164 litres if British or 180 to 200 litres if American. A lot of other sizes can be found, here are some of them:
English Tun: 982 litres| Gorda: 700 litres | Madeira Drum : 650 litres | Port Pipe : 650 litres
Machine Puncheon : 500 litres | Sherry Shape Puncheon : 500 litres | Sherry Butt: 478/500 litres
Cognac Barrique: 300 litres | Bordeaux Barrique: 225 litres | Hogshead: 250 litres |
Kilderkin: 82 litres | Quarter Cask: 50 litres | Blood Tub: 40 litres | Firkin: 41 litres | Pin: 20.5 litres Minipin: 10.25 litres | Barracoon/Barrack: 4 litres
What can be remembered about all these sizes is the different effect they can have on the wine stored in them. In general, the smaller a cask, the more powerful the aromas it imparts to the wine. That is to say that to a litre of wine, the surface that is actually in contact with the wood is way bigger, hence the difference. Very large oak casks, sometimes referred to as "foudre", can even be very close to neutral in terms of aromas.
Give Back to Caesar...
The invention of the barrel for transporting goods is attributed to the Celts, around 300 BC. After the Roman invasion, their invention traveled across the Continent, with the Romans trading around the Mediterranean Sea. These casks could allow to travel one way full of liquids and foods, and then to be broken down to make space for other stuff on the way back. Coopers were breaking down and rebuilding these great inventions, depending on the needs of each travel.
Enjoy Oak Responsibly...
However, if oak is great, the quality of good healthy grapes is vital in winemaking and oak will not fix the poor quality of a wine made of bad grapes. If a little touch of oak can add a dimension to the wine, too much oak can dissolve the elements of terroir and give wine a generic mass-produced taste, without all the beauty of its district of origin. For more info on terroir and tastes, check out the rest of our website. Cheers!
Certified Sommelier (CMS)