Barrel aging is an important and valued part of winemaking, especially when producing longer-aging wines. The aging process has many potential benefits, starting with greater stability, especially in terms of the wines’ interaction with oxygen.
However, obtaining the right results for each wine isn’t necessarily easy. As Nicolas Vivas, research director at Bordeaux-based Demptos cooperage points out, care has to be applied as you nurture the wines from fermentation to bottling. Barrel aging is an oxidation process, and if you go too far down that road, you can’t come back. “The general outlook you have to keep in mind is that this is a one-way process,” he says “There is no reverse on that particular machine. If you push things too far, quality will suffer, and that’s the foundation for any reflection on the subject.”
There are many different things at play in the art and science of barrel aging and the interactions of barrel-aged wines with oxygen. Nicolas Vivas has written several books about the topic, including one (in French) on the theory and practice of aging red wines. For starters, here are three key elements to keep in mind.
Look for Stability
“All the functions of barrel aging can be summed up in one word: stabilization,” says Vivas. The moderate, slow-paced interaction with oxygen changes the structure of the components within the wine, taking out certain things that need to go and adding in other things that will help the wine in the long run. “The chemistry is very complex, with this exchange between what goes out and what comes in. There are polysaccharides that are freed through autolysis and the small ones come and wrap around the tannins, which brings texture. Reduction gradually goes out. Tartaric acid goes out and so do solid deposits. And through oxygen, tannins get polymerized, which stabilizes them.” With the addition of oxygen in small doses, couplings between tannins and anthocyanins are also encouraged, largely because of the production of ethanal, an aldehyde component that helps bind those two phenolic components.
Careful management of lees (which help provide resistance against oxidation) and topping up (to moderate the oxygen ingress in the barrel) and careful monitoring are essential to providing that stability as well. If oxidative processes go too fast, the wine will obviously suffer, and remedial measures can only do so much. “If you build up too much acetaldehyde, a component that shows up through those apple skin, browned apple aromas, you can treat it with SO2, which will bind to the aromatic components, but you haven’t avoided excessive oxidation,” Vivas cautions. The resulting wine will have a lesser oxygen resistance, a shorter life—and its aromatics will be a lot less attractive.
Vivas also believes that one basic component is too easily forgotten: acidity. “It’s a fundamental factor that is easy to measure. When you move from a wine with a pH of 3.5 to a wine with a pH of 3.7, the wine is twice as oxidizable. Reactions are faster and the same reaction will have double the impact in a wine at pH 3.7. The oxidative environments are completely different, and the potential lifespan of a 3.7 wine will normally be shorter.” Wines with higher pHs feel rounder and richer, which makes them more attractive at a young age, but there is an aging tradeoff that has to be taken into consideration.
Although other factors like long and powerful tannin chains can come into play, to protect the wines, a wine with lower acidity should be considered as more sensitive to oxygen, and the barrel aging should be adjusted accordingly. “With a lower pH—say, 3.5 or 3.6—you can have longer and slightly more oxidative agings. With higher pH, you should look to gentler and shorter barrel aging.” Helpful precautions can include lowering the temperatures in the barrel room and limiting movement and other handling that could put more oxygen into the mix.
Pips, Skins, or Oak?
“The aging environment is linked to the wine’s composition, too,” adds Vivas, particularly pointing to the type of tannins that are at work. Tannins can come from three main sources: grape skins, grape pips, and the barrels themselves. Different types of oak may bring different tannin compositions to the mix, but the main variation is still between grape varieties and what proportion of their tannins come from pips or skins. “With Pinot Noir, Cabernet Franc, and other similarly-built varieties, the wines will have more tannins from the pips than from the skin. That means they are smaller tannins, which are more easily affected by oxygen,” says Vivas. But “With grapes whose typology is closer to Cabernet Sauvignon or Syrah, there are more skin tannins. Later-ripening varieties show less pip tannins, and their skin tannins are easier to extract. This leads to more polymerized tannins that are more resistant to oxygen and can take a bit more roughing up.”
Again, Vivas points out, oxygen ingress and the proper use of lees are crucial. “The wines of Burgundy show great complexity and aromatic length, and that comes from a well-mastered aging on lees. The polysaccharides, which come from the lees, bring length and aromatic retention.”
Whatever grapes or style, Vivas insists, the key is always to go slow and steady, with “small brushstrokes. Good barrel aging is like a pointillist painting, where you’re adding tiny dots of color to the canvas. It takes a long time, but the result is always remarkable.” In the world of wine, patience is usually the most rewarding virtue.
Photo courtesy of Napa Chauffeur.