Most of us know that the majority of red wines, almost all fine wines and even some white wines are all aged in oak barrels. The big question is why? What purpose does the oak serve? Are there any disadvantages? What are the advantages? How does French oak differ from American oak? Basically, what is oak all about?
Let's take a look at why oak barrels play such an important role in winemaking.
Photo Credit: A Room In The West End
The History of Oak Barrels
The earliest coopering (barrel making) practices date back to 2690 BC when straight sided, open buckets were used to transport liquids in ancient Egypt. It was only much later, during the Iron Age (800−900 BC), when the first fully sealed barrels were developed to hold wine, beer, milk, olive oil and water. It wasn't until the 1600s that European explorers really figured out the benefits of the oak barrel. The trade and transportation boom around the world was in full swing, and oak barrels had many advantages apart from being a storage vessel: they were strong and durable, their cylindrical shape made it easier to transport them from place to place by rolling them and, most importantly, it become evident that certain liquids, such as wine, benefited from being stored in oak for long periods of time. This is what created the cooperage industry, and why it is still thriving today.
If it weren't for the fact that oak barrels were initially used as storage vessels, and then the realisation that the oak actually benefitted the wine, it is highly unlikely that winemakers today would have ever thought of adding the dimension of oak flavour into their wine. So, we could say that it is a happy, historical coincidence that wine and oak form the perfect marriage to create a richer, more complex flavoured and textural wine.
How Does Oak Enhance the Wine?
There are two main things to focus on to understand how oak barrels enhance wine. While we could get very scientific and technical, not to worry, as I'll break it down in a very easy-to-understand manner!
Firstly, when red wines are ageing in the barrel, a process called controlled oxidation occurs, which is a slow, gradual process. This benefits the wine by reducing the astringency and increasing the colour and stability. With oxidation, a 300-litre barrel can lose up to 25 litres of liquid in a year, so winemakers need to continuously fill and rack (transfer the wines from one vessel to another) the barrels throughout the year. Racking helps to improve the clarity of the wine (a kind of natural form of filtering and fining), as well as allows the wine to receive enough oxygen that will help in enhancing the fruit flavours to become more complex flavours.
Secondly, there are five classes of chemical compounds found in oak. Each imparts its own flavour and texture to both red and white wines, the most common being vanilla, followed by sweet, toasty notes and lastly tea and tobacco. All of these compounds add to the overall complexity of the wine by augmenting the tannin that comes naturally from the grape (seeds, stems and skins).
Let's break down the five chemical compounds (this is the scientific part).
- Volatile phenols: Induce the vanilla flavours
- Carbohydrate degradation: Contains furfural, which imparts the sweet, toasty aromas
- Lactones: Add the "woody" notes
- Terpenes: Provide the addition of tea and tobacco flavours
- Hydrolysable tannins: Reduce the astringency to benefit the overall mouth feel
It gets even more technical, based on the different barrel-making techniques and the type of oak that is used. All of this has an impact on the overall flavour and texture characteristics of a wine. So, what exactly are these difference? There are many, and you will be amazed at how the smallest of these can play a big role in the outcome. Let's see what it's all about, shall we?
- American oak vs French oak
- Sawn wood staves vs hand split wood staves
- Boiling water, steam, natural gas or wood fire to bend the staves
- Natural air drying vs kiln drying
- Low, medium or high toasting
As you can see, barrels are extremley beneficial to the enhancement of wine in so many different ways. Both winemakers and coopers have different opinions when it comes to choosing the right oak for their wine, but that is what makes each and every wine so unique. We also must take our hats off to the coopers who make these barrels, as it is no easy task. Without them, we would not be able to enjoy the diversity of the drop we love so much.
Photo Credit: Barrel & Garden
French Oak vs American Oak
So, there are many pros and cons to using oak barrels, regardless of where they come from. Some of the pros we have already discussed, such as the great flavour extraction and well-intergrated tannins, which add quality and value to the wine, but what are the cons? One of the cons is price; oak barrels are very expensive. French oak is the most expensive and can range between US$850 and US$4,000 for a single barrel, compared to American oak, which can range between US$500 and US$1,500. Barrels also take up a lot of storage space and need to be stored in temperature- and humidity-controlled environments. Barrels are also very labour intensive; cellar workers need to constantly clean, top up and stir them. However, even though the cons may seem to outnumber the pros, oak barrels ultimately benefit the end product.
Next, let's look at the differences between the two major oaks that are used to better understand how they differ.
- Species: Quercus Petraea (European white oak)
- Has a finer grain and a richer contribution of aromatic components like vanilla
- Higher tannins, yet elegant, soft smooth wines are produced, due to the finer grain
- French oak typically comes from one or more primary forests: Allier, Limousin, Nevers and Vosges; the wood from each of these forests has slightly different characteristics
- Staves are hand spilt
- Wood fire is used to bend the staves and toast the barrel
- Natural air drying for 24−36 months
- Only 20−25% of the oak tree can be used
Flavours that French Oak induces based on the level of toast
|Light Toast||Medium Toast||Heavy Toast|
|Vanilla bean, caramel, baking spices||Cedar, cigar box, chocolate, baking spices||Crème Brûleé, cedar, cinnamon, ginger and clove|
- Species: Quercus Alba (North American white oak)
- Fast growing and wider grain, allows for more oxidation, making wines more intensely flavoured
- Lower tannins, but bolder, more powerful wines are produced, due to the wider grain
- Grown mostly in the north-central states of Minnesota, Missouri and Wisconsin; the wood from each of these forests has slightly different characteristics
- Staves are sawn
- Kilns are used to bend the staves and toast the barrel
- Kiln dried
- 40−50% of the oak tree can be used
Flavours that American Oak induces based on the level of toast
|Light Toast||Medium Toast||Heavy Toast|
|Vanilla, coconut||Honey/caramel, toasted coconut, coffee and cocoa||
Espresso, caramelised sugar, campfire
French oak can be more elegant, while American oak can be more assertive, although it primarily comes down to how the different oak types are used, just like salt and other seasonings. We know from experience that different foods have natural affinities with one another, whether it’s a spice rub for your barbequed steak or a dill sauce for grilled salmon. The same pairing concept applies to grape varieties and wood.
Cabernet Sauvignon, Pinot Noir and Chardonnay have a special affection for French oak, whereas Zinfandel molds better to American oak. Then you have Shiraz and Merlot, which love a bit of both. So, when it comes to blending differnet varieties, all sorts of elaborate oak aging might be used.
This is me filling French oak barrels with freshly fermented Chardonnay.
Hand Split vs Sawn Wood
Unlike wood sawing, which obviously uses a saw, hand split wood uses tools such as a hammer and wedge, splitting maul, cleaving axe, side knife and froe. How they differ is that hand spilt wood is split along the grain which results in a much stronger stave. The only disadvantage of hand splitting wood is that it is very time consuming, but it does result in a higher quality cut. This also adds to the overall value of French Oak by having a tighter grain that is stronger which also warrants an increased price tag per French Oak Barrel.
Natural Air Drying vs Kiln Drying
Kiln drying is a forced but controlled process where humidity and temperature are controlled using steam and fans. The drying process normally takes between 6−8 weeks due to the high temperatures. Air drying however, is a lengthy process which takes between 24−36 months.
Air dried oak is a known to be a coopers best friend, it is much easier to work with and is more stable than kiln dried oak because it is not forced dried through high temperatures, but rather by a slower, natural process. As the oak air dries naturally, the cells within the wood collapse slowly, causing them to compress and stay put, so when air dried oak absorbs moisture, it doesn’t swell as much hence it becomes more stable. Kiln dried oak will result in the cells collapsing quicker making the wood less stable and when moisture is absorbed, the cells expand rapidly.
The advantage of air dried oak is that it will be a lot stronger compared to kiln drying which can lead to oak becoming brittle and weak if not looked after properly.
Below is an example of how oak is air dried.
Photo Credit: Tonnellerie Allary
The Differences in Toasting Levels
- Suitable for wines which require minimal aroma enhancement and higher tannin content (Pinot Noir)
- Offers a significantly greater earthy aroma with mild wood notes.
- Results in the development of fresher flavours.
- Imparts significantly greater complex and toasty aromas.
- Longer toast periods result in a greater breakdown of Lignin, producing the stronger vanilla aroma.
- Overall taste imparted onto the wine is rounder.
- Offers greater notes of oak, vanilla, and caramel.
- Ideal for full-flavoured wines.
- Ensures nearly complete breakdown of the chemical components present in oak. (The volatile phenols, carbohydrate degradation, lactones etc.).
- Ideal for wines seeking a full impact of complex aromas and flavour notes with a lesser contribution of tannins to the wine structure.
- Imparts a deep smokey and roasted coffee taste and aromatic profile onto the wine.
Toasted Heads (Heads of the Barrel)
- You might be surprised to believe that the heads of a barrel make up 30% of the total oak surface area.
- Useful in reds with sufficient tannins, allowing for greater consistency in the wines characteristics.
- Works well with medium weight white wines (Chardonnay).
- Depending on the structure of the wine you are aiming to produce, it may or may not be beneficial to use toasted heads.
So whether it is French oak or American oak, different levels of toasting or different manufacturing processes, there are so many components to a barrel and how it is used in winemaking. In the end, it is all about the winemaker producing the best possible combination between the grapes and barrels to ultimately give us the consumer the satisfaction we long for.