The Role of Oak in Wine

It is a safe assumption to make that every person reading this article is aware that wood plays a role in the wine world.  Nobody is a stranger to images on every winery website of beautiful dim-lit cellars filled with oak barrels.  Oak is often one of the very fundamental basics a sommelier or wine enthusiast will bring into a conversation about wine, and there is good reason for this.


Oak is an absolutely integral part of the identity of a large number of wines.  Every factor from the type, size, age, grain, or treatment of the oak can directly affect the finished wine.  The details can get fascinatingly complex, at least for us wine nerds, and the science and biology behind why and how oak affects wine is incredibly well researched, starting from the very basics of studying the anatomy of an oak tree.


We’re going to make things a little more simple than that…


Firstly, a good place to start would be to mention that when we refer to oak we are generally talking about three specific types of oak:

  1. French Oak, Quercus Robur, and Quercus Petraea, which come from the oak forests in France.  The lions’ share of oak used in South Africa is French.
  2. American Oak and Quercus Alba, are grown throughout the Eastern USA.
  3. Hungarian/Eastern European Oak also known as Quercus Robur grown in…  You guessed it! Hungary or Eastern Europe.


These three types of oak all have fundamental variations that can play a significant role on the type of final wine produced.  These differences are mainly to do with the concentration of oak lactones, coarseness of grain, and amount of ellagitannins.  This seems like a mouthful of a sentence but the simplified version is this:

American oak typically displays higher concentrations of oak lactones than French and European oak.  This higher concentration is associated with stronger vanilla and coconut aromas.  French and European oak are known to exhibit more prominent soft spice aromas than their American counterparts as a result of the levels of a compound called eugenol.  American oak grain size is usually looser than the tight grained French and Eastern European oak which is why, along with their higher concentration of oak lactones, American oak imparts more flavour and increased aromatics on the wines compared to French and European Oak.


Furthermore, French Oak has a higher concentration of ellagitannins which leads to greater structure being imparted on the wine.  This is thought to contribute to the sense of astringency or oak related tannin levels making French oak an appealing option for premium wines as it gives structural support for wine to age.


Oak Compounds and their Aromas

VanillinVanilla and Coconut
Eugenol and IsoeugenolSpice and Clove
GuaiacolSmoke and Charred Notes


Oak is primarily used in the winemaking process for fermentation or ageing of wine.  New barrels (often referred to as ‘First Fill’) impart more flavour on the wine than older barrels (‘Second/Third/Fourth Fill’ etc.).  Old oak barrels are frequently used for fermentation and maturation, as they allow subtle micro oxygenation to occur.  Beyond stabilising the wines, this helps soften astringent tannins and enhance the overall integration of a wine.  Vignerons will work closely with Coopers to select their barrels in order to ensure the best quality and most suitable oak barrels are used in the production of wines.  Any decision that involves the use of oak in a winery is not taken lightly, especially considering the fact that barrels are incredibly expensive.  French oak is particularly expensive with most ranging between £700- £2,900 per 225L barrel.  Whereas American oak is the cheapest at an average of £300 per barrel.


The process of making a barrel can take upward of 3 years from when the tree is felled to be turned into the finished product.  The reality is that before the point of harvesting an oak tree, it needs to grow.  This is no small feat, given that American oak is only ready for harvest after 80-90 years of growth, whilst French/European oak takes an astounding 150-200 years before the tree can be harvested.  One oak tree can typically only produce two barrels.  225L of wine is only 50 (six bottle) cases.  Take a moment to imagine how many barrels a medium or large producer would need to purchase annually if the use of new oak is required in their wine making regime.  The numbers are mind boggling!


Naturally, oak barrels can be reused many times, but after 2-3 uses begin to lose their flavour and become ‘neutral’.  If a winemaker wants to highlight the flavours of oak in wine, the barrels will need to be regularly replaced.  These costs can become exorbitant.


Fortunately, there are alternatives to using barrels to add flavour which are more cost effective, such as oak chips or staves.  However, winemakers tend to prefer using barrels as far as possible for premium wines.  Coopers can also extend the shelf life of a barrel by shaving the inside and re-toasting it.  Unfortunately, this could compromise the structural integrity of the barrel making it weaker for stacking purposes and the toasting may not always be uniform.


With all of this information considered it begins to make perfect sense why your bold Bordeaux blend that has spent two years in new French oak costs you significantly more than a counterpart wine that has been aged in older oak or for shorter periods of time.  So, next time you’re standing in a winery’s beautifully dim-lit cellar surrounded by hundreds of their oak barrels holding quietly resting wine, take a moment to consider how many 150 year old oak trees are in the room.  For us, that is the epitome of seeing the ‘bigger picture’ and in that moment, the full appreciation for oaked wine will set in.


This blog was edited and posted by Digital Squeak.