For over 2000 years oak has been a fundamental component in the transport, maturation and production of wine. However, the adoration many wine lovers now hold for oak-aged wine emerged as somewhat of an accident opposed to an ingenious introduction. One could argue that the use of oak may well be one of the most influential tools in a winemakers arsenal, but how exactly does oak influence wine? In this post we will explore the history of oak, it’s uses, variations and much, much more …
As the Roman empire expanded aggressively across the globe they encountered numerous cultures, many of them possessing technologies which the Romans ’embraced’ When the Romans encountered the Gauls they found a people who were transporting beer in wooden barrels, bound together with metal hoops. Whilst the Romans themselves were indeed aware that earlier civilisations had used palm wood barrels to transport wine, until this encounter with the Gauls, amphorae were their transport medium of choice.
Whilst initially other woods were used, oak was popular for a number of reasons. First, the wood was much softer and easier to bend into the traditional barrel shape than palm wood, thus the oak only needed minimal toasting and a barrel could be created much faster. Second, oak was abundant in the forests of continental Europe. And finally, oak, with its tight grain, offered a waterproof storage medium.
After transporting wines in barrel for extended periods of time, the Romans began to realise that these oak barrels imparted new, pleasant qualities to the wine. They noticed that the oak contact made the wine softer and smoother, and with some wines, it also improved their taste. Due to minimal toasting of the wood, wines developed additional scents such as cloves, cinnamon, allspice or vanilla, and when drunk they had additional flavours such as caramel, vanilla or even butter, and a substantially different mouthfeel. Over time, merchants, wine producers, and armies alike, found that the longer the wine remained inside the barrels, the more qualities from the oak would be imparted into the wine, and thus began the practice of ageing wine in oak.
In the modern world there are three primary types of oak used in winemaking and all three differ greatly in the ways in which they impact wine. These three types are;
- French Oak – French oak is used frequently when ageing premium wines. It tends to impart flavour compounds in a more subtle and elegant manner compared to various other oaks, particularly American. Pinot Noir and Chardonnay appear to be an ideal match for French Oak, this could be due to the fact that they “soak up” flavour more easily than other grape varieties. French oak barrels can cost anywhere from £850 to £2700.
- American Oak – American oak tends to impart a great deal of flavour. Wine lovers often describe flavours lent by American Oak as dill, coconut, and intense vanilla. I find that it is able to add a sense of ruggedness to clean, fruit-forward new world wines. American White Oak grain sizes tend to have looser grains than both French and Eastern European Oak. American oak barrels cost around £200-350 per barrel.
- Eastern European Oak – Eastern European Oak barrels are derived from the same type of oak as French Oak barrels and are growing in popularity in many wineries. Eastern European Oak is most popular due to the fact that it is remarkably similar to French Oak, but costs much less. Barolo is a region in which Slavonian oak in particular is the barrel of choice, the Piedmontese lean toward a large capacity barrel that does not impart excessive flavour.Eastern European oak barrels cost around £400-550 per barrel.
Grain size is mentioned loosely above but it has a significant impact on the flavour the oak is able to impart upon the wine. The tighter grain in French oak lends itself to longer ageing potential (due to increased levels of ellagitannins) and contributes more spicy clove aromas and less of the toasted vanilla, brown sugar notes. The medium grain of American oak adds less tannin but more pronounced vanilla and caramel notes.
In the same way that it fundamentally composes the formation of compounds in grapes, terroir is crucial in the growth of oak and whilst this is not an area in which I have even a basic knowledge one can only assume that this provenance is vastly important in a cooper being able to choose the oak which best suits a vintners desired style.
In addition to provenance there are a number of other factors which vintners are able to stipulate to the cooper (barrel maker) and decide upon themselves which have the ability to influence the way in which the oak interacts with wine, these are toasting, barrel size and usage/recycling.
Exposing oak staves to a flame (toasting) helps break down sugars and tannins. As sugars change into simpler compounds, they more easily integrate into wine. Coopers will toast the staves more or less depending on the desired impact; medium+ toasting brings out more more vanillin and less tannin, while lighter toasting imparts more oak flavour and higher tannin levels in the wine.
In addition to toasting, vintners are able to stipulate the size of the barrel they require, this decision will often depend on the variety and intended aromatic/structural profile of the finished wine. When visiting Barolo it is commonplace to encounter barrels so large that one could comfortably walk around inside. The larger the barrel the more nuanced and less prominent the impact of the oak, this is due to less of the wine being in contact with the oak.
Oak barrels can be an extremely expensive tool for a winemaker, particularly the best quality French oak and it is rare that anything but the most expensive wines on the market will experience 100% new French oak simply due to the economic inviability of the practice. Winemakers have however found a way around this, recycling and additional use. It is commonplace for wines to experience a mix of first, second and third use oak barrels, as the usage increases the influence of the oak becomes less prominent, analogous to the diminishing influence of a tea bag upon second use. Additionally some winemakers, after multiple uses, will deconstruct their barrels and shave the staves to rejuvenate the influence of the barrels, essentially presenting a ‘fresh’ surface to the wine.
In true Word on the Grapevine fashion; let’s get geeky. We have touched upon types of oak, their characteristics and various vintner and cooperage choices, but precisely what are the primary ways in which oak barrels are able to alter wine and what EXACTLY does the oak contribute to the wine that has the ability to impact the finished product so profoundly …
In addition to providing a suitable environment for certain metabolic reactions such as malolactic fermentation to occur, oak barrels allow the slow ingress of oxygen, which in some sense is a form of uncontrolled micro-oxygenation. This ingress of oxygen helps to stabilise colour and improve astringency and aromatic components of the final wine. It is common knowledge among winemakers and those in the wine industry that the addition of oxygen affects chemical and sensory components of a wine.
Earlier we spoke about the gustatory impact of oak upon wine but why is this impact in some sense so predictable? Why are the same notes and descriptors so frequently used? Well it turns out that oak possesses particular chemical compounds (of which it shares with things such as clove) which can all be imparted upon wine. Each of these compounds are related to particular aromas, the most common of these are;
- Furfural – dried fruit, burned almond, burnt sugar
- Guaiacol – burn overtones
- Oak lactone – woody, dill and coconut notes
- Eugenol – spices, cloves and smoke character
- Vanillan – vanilla notes
- Syringaldehyde – further vanilla-like notes
As previously mentioned, the scale at which oak is able to influence the flavour of wine is subject to various decisions made by both the cooper and the vintner. Use of oak is a divisive topic, there are many who love it and many who do not. However, there is no debating that the use of oak is synonymous with many of the worlds most iconic wines and I believe will be for many years to come, I do however believe that the way we grow and use oak may change in future years dependent on climate and economy.
As always I hope you have enjoyed this post and that it has helped you understand the use of oak in winemaking.