Why Is Wine Aged In Oak Barrels?

When you think of vineyards, wineries and other aspects of the wine making process, one of the most identifiable images that comes to mind has to be the oak wine barrel.  And one of the first questions that pops into mind is, why is wine aged in oak barrels?

Let’s find it out!

Wine Aging - A Brief History

Perhaps no other piece of the production process has become as iconic as the oak wine barrel has become.  For what reasons did people begin to age wine in oak barrels in the first place?  After all, in the earliest of times, clay pottery was the standard storage of choice for both the transporting and storing of wine. 

The use of clay pottery continued to be used up to and including the time period of two thousand years ago, as the Roman Empire began to spread across the globe.  The Roman Army would take wine, weapons and food with them, since wine was safer to drink than water. 

As they pushed northward into Europe and away from the Mediterranean, the use of clay potteries to transport the wine became more and more difficult.  It was when the Romans came upon the Gauls, that they discovered a group of people that were using wooden barrels to transport beer, and these wooden barrels were often made of oak.

The Romans soon realized that they no longer needed to haul the heavy and easily breakable clay containers around with them.  Oak, unlike other types of wood, was soft and relatively easy to bend into a barrel shape.  This made barrel making a quick process.  Also, as the Romans proceeded into Europe, they found that oak was extremely abundant in the vast forests, giving them a rich supply of the wood.  They also discovered that this abundant oak had a tight grain and was easily bendable, and could easily be constructed into a lightweight yet sturdy storage container.  Thus, the transition from clay to oak occurred and the process of change happened rapidly.

After some time had passed, the Romans began to realize an unintended consequence of transporting and storing wine in oak barrels.  The oak barrels were found to have added new and pleasant qualities to the wine.  The Romans discovered that as the wine was aged in the oak barrels, it became better tasting, often presenting a smoother and softer taste.  These oak barrels also would give the wine a more aromatic quality along with added flavors of caramel or vanilla. 

After this discovery, it did not take long for the Romans and other societies that they encountered to realize that the longer the wine remained inside of the oak barrels, the greater the number of qualities of the oak would find their way into the wine.  This is what eventually led to the practice of aging wine in oak barrels.

It can be said that due to the long standing practice of using wooden barrels for wine storage and transportation during the Roman Empire, it is highly unlikely that the winemakers of today would have even thought of adding an oak flavor to their wines.  Many historians thus believe that it is a fortunate coincidence that wine came together with wood to form a richer, more complex flavor than ever would have occurred had the oak barrel never been discovered.

How Does Oak Barrels Enhance the Flavor of Wine?

So after all of these centuries since the “accidental” discovery of aging wine in oak barrels, why is it still such a popular process with today’s vintners? We have to ask ourselves, what exactly does an oak barrel impart to wine?  How does it enhance it?  There are at least two ways that wine can benefit from its contact with oak. 

First of all and this is mainly true with red wines, aging the wine in an oak barrel allows for controlled oxidation.  As the oxidation is controlled and gradual, it allows for decreased astringency of the wine, along with an improvement in color and stability of the wine.  At the same time, it allows the existing fruit aromas to evolve into more complex and pleasing aromas. 

Secondly, the oak used in the making of the barrels is often composed of several different chemical compounds, each of which, over time, will contribute its own flavor and notes to the wine.  The most notable of these include vanilla flavors, as well as sweet and toasty aromas.  The compounds in the oak barrels that create these improvements in the wine include phenols containing vanillin, carbohydrate degradation products that contain furfural, a component that yields the sweet and tasty aromas, oak lactones that give the wine a woody aroma and hydrolysable tannins which are important to the relative astringency of the wine.

Now that we have learned that the oak used in the wine aging barrels can be composed of several different chemical compounds, wine makers of today are understandably often very particular about the type of oak barrel that they use. 

There are subtle differences in the flavor and texture of wines that are purely dependent of the barrel manufacturing technique and the type of oak used.  The different types of oak include American oak,  French oak and Eastern European oak, and other variables include if the oak is sawn versus hand-split, air dried versus kiln drying, and whether the use of boiling water, steam, natural gas, or wood fire to bend the oak is utilized.  You can see how easy it would be for a wine maker to create their own type of oak barrel that best suits their particular style of wine.

Different Types of Oak and Their Effects on Wine

Do different types of oak really add different qualities to the same wine?  French oak contains the highest amounts of tannins of the oak types.  French oak is also more porous than the other oak varieties, allowing the qualities of this oak to more easily contribute to the flavor of the wine. 

French Oak traditionally is known for giving wines notes of spice.  American oak is a stronger wood than its French and Eastern European varieties.  The structural differences in American oak result in more intense vanilla flavors, wood sugars and toastiness. 

American oak is much cheaper than its French cousin, leading to lower cost barrels with several popular traits. 

Eastern European oak is more closely related to the French oak than it is the American oak; however it has different qualities, including less tannin.  Eastern European oak also breaks down more easily, which forms a different type of toasty aromas than that of the French and American oaks. 

Not only does the type of oak used in the barrel matter, but the size and age of the barrel also matters.  In addition, the time that the wine spends in the oak barrels matters considerably as well.  A newer and smaller barrel will have a stronger influence on the wine.  This is due to the fact that in a smaller barrel, a higher percentage of the wine in that barrel is in contact with the wood as compared to a larger barrel. 

Once a barrel has been used a few times, the effect on the wine begins to soften and become less discernable. 

Older barrels that have been used several times may no longer add any flavors to the wine, but still play a very important role.  This is because of the small amount of oxygen that oak allows to permeate the wood.  This tiny bit of oxygen still has a large impact on the natural chemical conversion that wine undergoes as it ferments and ages. 

This process can be seen in white wines, where it influences the development of certain aromatic compounds.  In red wines, the impact of oxygen is often more crucial, as the color and tannin of the grape skis need oxygen to form stable phenolic compounds, and the oak’s tannins themselves support the structure of the red wines.

For How Long Should You Age Wine?

So how long should wine be aged for in an oak barrel?  What determines the optimal amount of time to age a wine? 

Well, taste is obviously the most important determining factor of how long a wine should spend inside of a barrel, since aging wine in an oak barrel is done in an effort to impart the correct level of flavor and structure to any given wine. 

Something to consider also is the fact that once wine is bottled, the oak flavor that was so carefully added to the wine during the aging process, will mellow out a fair amount.  Due to this fact, wine makers will often wait until the wine has slightly more oak flavor than one would typically prefer to bottle it, as this oak flavor will diminish by the time it is enjoyed. 

One technique that wine makers often use when aging wine in an oak barrel is to hold back a portion of the wine prior to placing the rest within the oak barrel.  They then store the saved portion in stainless steel or glass so that absolutely no oak flavor is added to this portion of the wine.  Then, once their wine is finished aging in the oak barrel, if the taste is too strong, they simply add some of the held back wine to the finished wine until the perfect flavor balance is achieved.

We can now see how an “accidental discovery” of the benefits of aging wine in oak barrels has shaped the landscape of the wine making process of today.  Without the oak barrel, wine would not be what wine is today.