Most of us have not explored deep into the world of oak. Why would we? However, chances are you know that oak can impart tannins, or vanilla, or char (depending on what you are drinking). You have most likely had some buttery, flabby, aggressively over-oaked cheap Chardonnay at some point.
There is actually quite a bit to know about oak, from the basic scientific rationale behind oak aging (why not age in plastic? Or clay? Or any other container?) to the varieties of oak used for aging, and what they can impart in your favorite wine, beer, or whisky.
Oak was Not Always Used to Age Wine or Spirits
Ancient Romans were transporting their wine in massive, hulking clay amphorae. Only when the Romans encountered the Gauls using oak to transport beer did they realize a few things: oak was lighter than their giant, impressive-looking clay amphorae; oak had a tight grain so it could hold liquid but was more flexible than previously used woods like palm; and you could actually roll oak barrels, meaning a lot easier transport and a lot less backache.
With regards to ageing wine, only when the wine inside the Oak began displaying the beneficial effects of contact with oak that the concept of intentional aging came about.
How Oak Impacts Wine
The origins of wood barrels stem from clay amphora and other various ancient wine storage and transport containers that were used.
Barrels have evolved into more than simple storage vessels. When wine maintains contact with wood during the fermentation and aging process, it undergoes profound modifications thanks to extractable organic compounds
That’s technical biochemistry, but it translates to our most primitive experiences with wine: smell and taste.
Each barrel has a life of its own, chosen to develop and contribute certain qualities to the final wine’s profile.
New oak brings an aromatic and gustatory complexity, while old oak, depending on its age, tends to become more neutral year after year.
New barrels, fresh from the cooperage, have been “toasted,” or exposed to a flame for a certain time and temperature depending on the style of the toasting of the inside of the barrel causes compounds in the wood to degrade into a volatile form that can influence the wine as the level of toasting changes, so too does the volatile compounds and thus the influence.
The Nuances and Flavour Impact of Toasted and Aged Oak
The impact of the toasting process declines as barrels age with use, and they edge toward a neutral state.
Neutral barrels can still play a big part in a wine. Think of the barrel as a vessel that ‘breathes’ as it releases slow amounts of oxygen into the wine, which has the effect of softening tannins and improving weight or texture.
Some winemakers use a mix of new and old oak throughout the cellar, even in the making of a single cuvée. New oak influences in red wines are different than white wines. New oak will open the aromatics of the white wines, while it will sublimate the tannic structure on red wines.
However, most of the time it is still a mix of new oak and older oak, in order to not have the oak flavour cover too much of the delicate primary aromas of the variety of grape(s).
Size of Barrel
The larger the barrel, the less oak lactones and oxygen are imparted into a wine. Barriques are traditionally 225 liters, whereas Botti and Foudres are much larger – from about 1000 to 20,000 liters.
Basic Types of Oak
French oak— Quercus robur—is a white oak historically found in abundance in the forests of eastern and central France. There are a few major regions that produce the French oak used for aging: Troncais, Nevers, Allier, and Vosges. There is also the famous Limousin oak, from the heavily guarded forests of Limousin. (Quercus robur comes exclusively from Limousin oak, which is more tannic.) Though the oaks within France vary, French oak tends to have a slightly softer impact, with subtle spice. Generally tighter grained, except for Limousin, French oak will impart smooth but substantial tannin.
Also known as Quercus alba, American oak has a lot of hemicellulose, which, when charred, will break down into wood sugars, allowing for some caramelization. This is important when you think about the classic caramel/toffee/brown sugar notes of bourbon—which is, by law, made in charred new white American oak barrels. American oak is also fairly heavy in lactones, which can impart woody but also tropical (think: coconut, banana) flavors. Whatever is aged in American oak could tend to get a bit more of a pronounced creaminess and flavors associated with vanillin.
Russian/Eastern European/Caucasian Oak
The farther East you go, the more you will encounter Quercus robur. Eastern Europe has a vast supply of oak trees. Hungarian oak is richer in eugenols, which impart spice, and tends to create a slightly richer mouthfeel with substantial tannin. Not that you will find too many differentiations on the back of a wine bottle, but Caucasian oak (as in from the Caucuses) imparts less tannin and aromatics, which is useful if you want a fruitier, straight-up expression of the grape itself. Interesting to note, Russian oak is not exclusively used in Russia. It is used widely, for various reasons. Same goes for Slavonian oak, which will give less tannin and impart more sweetness, and it is used in a variety of Italian wines.
The Importance of Oak
We can safely determine that oak has become the most accepted way to affect the taste of a wine. When added to wine, oak flavours combine with the flavours to create a wide variety of potential incredible flavours.