After you press the must what you have will certainly resemble wine but it probably won’t taste too much like it just yet. All of the flavor, the complexity, and the nuance come out only after it has been aged. There are a few different options when it comes to aging wine, sometimes it is aged in stainless steal tanks, more and more you hear about people using concrete vats, there is even something around called an egg, but what is most common in winemaking and what has been used since Roman times is the oak barrel. From very early on people realized that wine tasted better after it had been allowed to age and that aging it in an oak barrel not only allowed it soften it also imparted some of the oak flavors into in the wine.
Before we go into why those changes happen and how exactly the barrel affects the wine we should first talk about how barrels are made. It may not seem like an important step to learn about but the technique through which the barrel is made not only showcases where the flavors of the wood come from it is also one of the first steps a winemaker takes in dictating the final flavor of their wine. A barrel begins with a tree. Where this tree comes from is one important factor to consider because the climate in which the tree grows, much like with grapes, dictates how the tree grows. Tress that are grown in a cooler climate tend to grow slowly, forming small tight rings, while trees that are grown in a warm climate grow faster creating bigger, wider rings. These rings are what form the grain of the wood, so the closer together the rings, the tighter the grain of the wood. Winemakers tend to prefer close-grained wood because the dense flavor packed into that small space is extracted more gradually, meaning almost all barrels are made from trees grown in cool climates. And not only that, those trees are only harvested after they are 100 years old, or older. Barrels, kind of a rare resource, yes?
Add to that the fact that the best coopers still hand split the oak staves and then allow them to air dry and season out in the elements. This seasoning process takes about 2-3 years. The reason behind this process is to make sure the harshest tannins in the wood are leached out before it is ever formed into a barrel. The next step in the process is to actually form the barrel. For this the cooper wants the staves to fit as close together as possible and to do that they heat the staves over an open fire to make the wood pliable enough to bend. This process is yet again traditionally done by hand, the cooper uses winches and chains to bend the wood and then iron rings that are hammered down to hold the staves in shape and in place. The fire is not just used to make the wood pliable, it is also used to toast it, essentially caramelizing the natural sugars in the wood and giving it a toasty, spicy, vanilla flavor that will eventually be imparted into the wine. This is where the winemaker’s choice comes into the picture, they can order their barrel toasted to their preference and their needs, from lightly toasted to well toasted depending on what kind of flavor or what intensity of flavor they want to impart to the wine.
Because one of the factors in a good barrel is a cool climate to produce a tight grain the trees for barrel making only come from a few specific locations. The two main types of oak used for winemaking are American Oak, typically grown in the Midwest, and French Oak, grown in central and eastern France. The flavors that these two types of barrels impart, even if they are made with the same technique, are pretty different. American oak is much more pronounced in flavor with strong notes of vanilla which French oak is considerably subtler. Because of these differences certain, more delicate grapes, like Pinot Noir for example, are only ever aged in French oak barrels, as the prominent flavors of the American oak would overpower the wine.
Now we can get to the wine and how the barrel interacts and affects the wine. Like I said before people discovered very early on that aging in oak barrels soften the wines. And while the Romans may have noticed this change and made sure that they continued to age their wines in oak, they probably didn’t really know why it made a difference. But today we have a little better understanding of what is happening. There are actually two different processes occurring in a barrel: evaporation and oxidation. No matter how good of a cooper you have or how cool of a climate the tree was grown in there are always going to be spaces in the wood, and that is actually the beauty of the barrel. Water and alcohol are slowly evaporating through these minuet openings and at the same time oxygen is coming in. These two processes are what help to marry the flavors of the wine and allow it is slowly age and soften. Aside from these processes the oak barrel also imparts some of its own flavors into the wine, adding another dimension of flavor and complexity to the wine. The wood it self is composed of different chemical compounds that help to change the wines aroma, flavor, and texture. It is these chemical compounds that impart some of the classic barrel associated flavors like vanilla, tea, tobacco and baking spices.
The type of barrel wine is aged in a crucial choice in determining the flavor profile of the wine you are making and the aging process is a crucial step in turn that stuff that looks a lot like wine but tastes a lot like juice into something you actually want to serve with your dinner.