Concha y Toro

Ania Smolec 03/05/2017

How oak barrels affect the character of wine?


Vintage films print an image of the wine always associated with a barrel. But today it is nothing more than a myth. Some wines have no contact with wood, but a passage through the barrel adds new layers to its personality. I invite you to the world of barrels.

Why is the wine made and stored in oak barrels? Before the glass bottles appeared, most of the wines were transported and sold in wooden barrels. Today, oak barrels are an integral part of modern winemaking.

Oak brings three dimensions to the wine: aromas; the slow inlet of oxygen, a process that makes the wine’s taste softer and less astringent; and provides a suitable environment for certain metabolic reactions (specifically malolactic fermentation, which transforms malic acid into lactic acid), which makes wines more creamy.

Unequal barrels


The barrels have different characteristics that influence and sometimes mark the style of the wine.

  • Different size and shape: the traditional barrel of Bordeaux has a capacity of 225 liters and the Burgundy barrel, 300 liters. These are two of the most used in the world. It is a standard and makes it easy to work in the cellar. Of course, there are smaller or larger ones. The smaller the barrel, the greater its influence on the wine.
  • Origin of barrels: The oak comes from different countries and adds flavors and textures to the wine. For this reason, the technical sheets specify if the wine is made in French or American barrels. However, there are many other origins. Hungary and Slovakia are the most demanded outside the United States and France.

French oak is subtle, while the American is very intense. To be more specific, French oak has a finer grain (the air spaces are smaller). This prevents the wine from penetrating very deeply into the oak, thus reducing the contact surface with the wine. The result is a delicate oak flavor.

American oak, on the other hand, has a bigger grain. The increase of the contact surface allows a greater extraction of flavors and tannins of the oak. In addition, other types of wood are used in several countries, such as chestnut, acacia, Iberian or English oak. In Chile, traditionally, winemakers used (and some still do) an indigenous tree called Raulí.

What the barrels deliver during winemaking

The barrel for wine may be new or used. A new one, of course, adds more aromatic components. With age and with each use, the barrel has less effect. The new wood breathes better than the old one, because its pores are not closed by the deposit wine, and oxygen penetrates the liquid easily. The new oak adds more tannins and softening substances from the cellulose of the wood.

BarricasOak affects not only the wine’s taste, but its chemistry. It is important to understand that not all oaks behave in a similar way. An average barrel allows a percentage of wine to evaporate over a year. This is why winemakers have to fill their barrels and why the aroma in the wine cellar is so good! As the wine evaporates, water and alcohol are lost, while the flavors and aromas are concentrated.

On the other hand, oxygen penetrates in very small quantities. This micro-oxygenation (an excess of oxygen turns the wine into vinegar) helps the wine to ripen and lime its edges.

Phenols are the compounds found in grapes and oak and make up the flavor, aroma and texture / weight of a wine. There are hundreds of different phenols in a wine. Most come from the grapes, but the oak can also impart some of their own. These phenols can be combined to form new flavor compounds.

The main aromas that the barrels give to the wine during the aging are: vanilla, cinnamon, cloves, curry, smoky notes, coconut, dill, caramel, toasted almond, dried fruit, coffee beans

The taste profile that the oak imparts in the wine depends on the different degrees of roasting of the barrel. Toasting is a necessary process that makes the staves flexible enough to bend them to the final shape of the barrel.

During this process the wood is slightly carbonized, as you can imagine. The barely roasted oak gives more green or immature flavors, while a deeper or heavy one produces flavors of vanilla, mocha and caramel. The four most common levels are: light, medium, medium plus and heavy.