Oak, if it were to be understood in an analogy from a gastronomic viewpoint, is to a winemaker what salt is to a chef. When looking at your wine's label, you'll most likely come across a description that includes the type of oak used and how it was used to produce the wine. It's been this way for centuries, as oak and winemaking have been allies since at least two millennia ago. Wines that are usually produced with the use of oak are big white wines and some red wines. But why is this? Why is oak used? What is the difference between American oak and French oak? And furthermore, what does it add to our wine?

Before these questions are answered, it might be best to start with the oak itself and its origins of use. The use of oak for wine began about two millennia ago during the Roman Empire. At first it was utilized because it made a better storage vessel for wine than the original amphora made of clay, ceramic and other materials. Other than its more convenient utility, oak was noted to impart softer flavors into the wine it stored, making the wine taste better. (Learn more in our feature, "Wine and the Ancient Roman Empire.")

Why Oak Instead of Other Woods?

Other woods can be used and are used. In Greek Mesopotamia, palm wood was used. Many other wood types have been utilized and are still in use today such as cherry, chestnut, acacia and ash. Although some winemakers might choose these out of their desired results, some use them as they are much more affordable alternatives. Oak, however, has many different qualities that make it worth its cost.

Oak, compared to other alternatives is much easier to shape into a barrel. It is also one of the most abundant woods available and one of the fastest growing. Oak is also coveted for its ability to retain liquids inside due to its tight grain, yet it possesses the ability to allow contents to "breathe." The oak barrel can remain water-tight, however, its pores allow for a controlled and necessary evaporation to take place.

The origins of the oak predominantly utilized in wineries worldwide originate from France and North America. However, in Italy, winemakers have been known for generations to use Slavonian oak which falls within one of the three major oaks used to make wine barrels: Eastern European Oak, which is the category for Slavonian oak; French Oak and American Oak are the other two. For French oak, there are five notable forests in France where oak is harvested to produce winemaking equipment: Limousin, Nevers, Trancáis, Vosges and Allier. Though the oak in each forest may be from the same species, Quercus Robur or Quercus Petraea, each have their own characteristics. You might be familiar with the characteristics of terroir and how it has different elements which contribute to wine depending on geographic location. Oak, when utilized in wine, depending on its origin, can also impart varying characteristics into wine. (Learn more in "Wine and Wood: Combining Tradition With new Techniques.")

The oak harvested from North America for the use of winemaking is derived from Pennsylvania and Oregon. However, there are cooperages (barrel-making houses) that use oak from 16 other eastern states. The species of oak utilized for wine barrels in North America is Quercus alba.

*Interesting fact: The tree utilized for cork, also very important in wine production, is a member the oak family, Quercus suber.

Now that you are familiar with the origins of oak, both in where it is harvested for wine barrels and its usage in winemaking, we can begin answering other questions.

Why is Oak Used in Big White Wines and Red Wines?

When winemakers decide to use oak for the elaboration of their wines, there are a few considerations of why they wish to use it.

  1. The balance of the wine’s profile from its aromatics to its palate could use a "correction."
  2. The wine could benefit from aging, including a controlled evaporation.
  3. The wine can be enhanced and thus fit the profile a winery might desire in its overall portfolio of wine. It might even be more marketable.

What is the Difference Between American Oak and French Oak?

When oak is utilized to age and enhance wine, there are certain characteristics which are imparted into the wine. It influences organoleptic aspects from its color, aromatic profile and body/texture profile. These will be addressed in a moment. However, American oak will offer different characteristics to a wine in comparison to French oak and vice versa.

The pores of American oak are much looser than its counterpart in France. This will introduce characteristics much quicker into wine. These characteristics are also very different and specific. American Oak is known for the bold notes it lends to wine such as dill, coconut, vanilla, pencil shavings and cedar.

When oak barrels are made, fire is needed in order to bend the wood. The barrels are often further kept over the fire to toast the inside, hence the term "toasted barrels." There are about 4 different toast levels for oak and this often varies on the cooperage. The extent of the barrels' toast level can also have an influence on the aromatics and flavor profiles imparted into wine.

French oak, in contrast to American, is known for having much tighter porosity. This means that characteristics from the oak are blended into the wine much slower. French oak is known for other elements it lends to wine, like notes of warm spice (cinnamon, clove, nutmeg, etc.), soft vanilla and caramel. Just as in toast levels of American oak, the toast levels of French oak can also vary, thus creating other wine characteristics.

Regardless of the oak barrel used. Once the barrel has been used four times, it no longer imparts any characteristics into wine. Sometimes these barrels are still used, but for lighter style wines in which no or very little oak characteristics are needed.

How Oak Influences Wine

Color

The influence of color oak has is more noticeable in white wines. A white wine which has been "oaked" takes on a more golden hue. This is not only from the oak itself but from the controlled oxidation of the wine as well. For red wines, it is less noticeable, but oak has a way of stabilizing the color of red wine. This enables the wine to retain its color even with age once it is in the bottle.

Aromatics

As you have read above in terms of American and French oak characteristics which are imparted into wine during its aging in oak, you can see there is much variation. The above listed from both French and American oak, i.e., pencil shavings, coconut, spices, vanilla, etc, are only just a few examples. A barrel can be lightly toasted, heavily toasted and many levels in-between. Sometimes the barrels are also toasted on the top and bottom. All of these aspects give the wine particular aromatics which affects the scents a wine taster experiences upon each visit to the rim of their glass.

Body/texture

Regardless of the oak utilized, it will impart many characteristics influencing the mouthfeel, texture and body of a wine. The most well-known element is tannin. To explain tannin in a way you can easily understand; it is the texture you note when drinking a cup of unsweetened tea (no cream or milk). The tea takes on a bitter taste and the texture dries one’s mouth. Tannins exist in many fruits and vegetables as well; unripe avocados, peaches, green tomatoes, apples, green beans, etc.

Tannins also come from the wine grapes as well, however, in wine, they are only really noticeable in reds. This is because red wine is made in contact with the skins of the grapes (which also introduce characteristics: color, aroma and texture/body). If a certain grape has a noticeable amount of natural tannin from its skins, the wine will be balanced out to impart tannin from oak. This balances out the palate of a wine. The more tannin and other characteristics elaborated in the wine, the more body/texture it will have. (Learn more in "What Balance Means in Wine.")

Why is Oak Used More for Reds Than White Wines?

White wines are not fermented with their skin, rather the grapes are pressed prior to fermentation and the juice alone is fermented. Thus, there will be lesser tannin to be imparted into the wine from the skins. Oak is also rarely used for white wines because of their delicate nature. Oak, if not used with discretion, can take over the delicate characteristics of a white wine, in its aromatic notes, flavor and texture.

However, it is widely known that Chardonnay is a popular varietal to "oak" as is the famous Fume Blanc, an oaked Sauvignon Blanc.

Now that you know how and why oak is used in wine, you can better choose the kinds of wines you're interested in drinking and trying.