Barrel cellar: here’s why to lower temperature
Temperature has a huge impact on the evolution of wine,” says Vivas, and climate change is also affecting the degree of chilling in the cellar. What happens between wood and wine at different temperatures, how it changes between large and small barrels and between white and red wines. How to manage aging to achieve modern organoleptic profiles that respond to changing climate, but also consumer tastes.
Lowering the temperature in the cooperage, although economically expensive, may prove to be the right move to better manage the aging of wines that are increasingly the offspring of hot vintages, guaranteeing and preserving their freshness and fruit. The trend comes from Bordeaux, where the use of wood is a kind of religion, and to understand how it works, in oenological and physical terms, we turned to the man who is, to all intents and purposes, a true priest of this religion: Nicolas Vivas, among Bordeaux’s most renowned oenologists, a researcher at Victor Segalen University and, indeed, among the greatest experts on the interaction between wine and wood. “Exactly as it happens with pH, temperature has a huge impact on the evolution of wine and the chemical reactions involved,” Vivas explains. We need a minimum amount of energy to support the wine’s chemical processes, but if we increase the temperature, the amount of energy available for these processes also increases proportionally, thus increasing the rate of wine evolution. Conversely, by lowering the temperature, the wine has less energy available and therefore fewer chemical reactions.”
And how does temperature in the barrel cellar, and a lowering of it, impact the aromas of the wine?
Aromas in my opinion are nothing more than the consequence of that great chapter of wine chemistry we call “oxidation.” Facilitating oxidative reactions is crucial, because by increasing them, the overall rate of wine evolution increases. If oxidation occurs too quickly, however, one of the consequences is to produce more ketones and other aldehydes (compounds that form naturally in wine during the alcoholic fermentation of must, but are more noticeably present in oxidized wines and communicate a particular bitterness,), with the risk that the alkyl radicals of the ketones bind to the molecules that give the fruity aromas to the wine (e.g., ethyl butyrate, a key molecule in the aroma of several berries, ed.). What happens at the aromatic level, however, is not a direct consequence of temperature, but of a too fast evolution of the oxidative process.
Why, then, is it decided to change the way we manage cooperage temperature?
The main reason is climate change: increasingly warm growing seasons deliver us generally overripe grapes, and this has consequences on two parameters. The first is pH, which will be higher, leading to an increased sensitivity of the wine to oxidation. There is therefore a need to rebalance this, and the best way is to add corrective (reductive) products in the wine or lower the temperature of the wine. The second parameter that results in over-ripening of the grapes is the increase in spicy hints. The real need is to protect the fruity part of the aromas and the solution, again, is lowered temperatures so that there is less oxidation and fewer compounds that can capture the fruity aromas.
What results will we get in the bottle?
The goal is to ensure wines that can retain freshness and balance. More generally, year after year, it is becoming wiser to age wines longer but at lower temperatures. We want to produce wines that respect the fruit and freshness, not only the fruity character, but also the notes of mint and licorice, which give lightness and elegance to the wine.
What are the differences in handling a large cask and a small cask?
There are, of course, differences, because it is on the size that the amount of oxygen with which the wine comes into contact depends. The larger the barrel, the less oxygen will be transferred to the wine. And then there is the woody, overall character that the wine will have: the larger the barrel, the less this character will be transferred to the wine. Temperature management also depends on the size: a 2-5 hectoliter cask needs lower temperatures than a 5 or more hectoliter cask, precisely because there is a greater amount of oxygen to manage and therefore a greater sensitivity of the wine.
What changes between aging a red wine and a white wine, even in terms of temperature management?
Whites and reds have very different ways of evolving. For red wines, we need oxidation to promote tannin polymerization and color stabilization, as well as a more stable form of polyphenols. For white wines, on the other hand, aging in wood allows a stabilization of the wine, which occurs in reduction, because by oxidizing a white wine would lose freshness, color and quality. In addition, to add complexity between the character of the wood and the wine, in whites there is a need for a minimum of oxygen, which gives the white wine the ability to resist oxidation. The reason temperature management is infinitely more important in reds is that the aging process is longer, so great care is needed in temperature management, especially when working with particularly delicate varieties, such as Sangiovese or Pinot Noir. In whites, aging times are shorter, and some times aging takes place on the lees, so there is a need to facilitate autolysis of the fine lees, a process that needs a certain temperature.
