Reproduced from Year 4, Issue #18 of Spirito di Vino Asia...
Oak usage in winemaking has had a bad rap lately. Perhaps it is justified in some cases, but one thing is sure, the technique is not recent. Hundreds of generations ago, oak was the main material utilized for fermentation, maturation, and transportation of wine. What has changed in recent times, for better or worse, is how oak is applied at various stages of winemaking.
It is undeniable that oak has a fundamental influence on both style and quality for it can affect aromatic complexity, alter texture, and improve stability. Key is whether it enhances quality and help produce a wine in harmony with its intended style.
The first choice, before deciding on the various options available for oak, is whether the wine will be made in an oxidative or a reductive style. An oxidative style is one in which minute amounts of oxygen are allowed to percolate through the wine over a period of time in a controlled environment. Oak usage is a key, but not the only, factor to achieve that effect. This technique adds empyreumatic notes to the nose, and generally tones down the aromatics while at the same time gives a supple mouthfeel. Contrastingly, a reductive style is obtained by protecting the wine as much as possible from the effect of oxygen. At the extreme, it will be made in a completely inert environment in stainless steel vessels and with the help of nitrogen and/or carbon dioxide. The result is a wine that emphasizes its aromatic freshness and vibrancy of texture.
Oak influences wine in several ways. The most important is the effect of the wood itself being exposed to the wine for it impacts its aromatics and help to stabilize it. As we will see, oak can have aromatic compounds that release into the wine and increase complexity. However, it can also draw out aromatics resulting in toned-down bouquet. The wood can also release its tannins and bind with those of the wine to help to harmonize texture and stabilize color. However, most of the effect of wood is to absorb wine tannins and decrease their harshness in the final wine.
The second most important effect principally comes from the opening used to fill an oak vessel as it exposes the wine to tiny amount oxygen during maturation and handling. Two important transformations occur, that of controlled oxidation creating an oxidative style and that of concentration through evaporation of water and alcohol, up to 5-6% per year, rendering the texture more sumptuous, and the aromas more intense and complex.
There is today, an amazing number of options available to the winemaker related to oak. First, different species behave differently because of their very nature. American oak is tighter in grain and more aromatic compared to French oak which generally looser in grain allowing slightly more oxygenation and gentler in aromas. The vessels themselves come in several sizes and the smaller they are, the faster and more important is the oak’s influence. New oak, also known as “first passage”, releases the most compounds and after 4 uses, the vessel basically becomes neutral and very little compounds is released into the wine. At this stage, the vessels are used mainly for their thermal properties, and their now very slow oxidative influence. Finally, oak barrels are usually toasted at various degrees during their cooperage which will greatly influence the nature of the compounds released in the wine. Lighter toast releases aromas of sweet spices while higher toast releases coffee and roasted nuts among others.
Today, alternatives to casks and barrels are used to great effect and with such skills that even the finest palates can be mistaken. They include chips and staves that are gently macerated into the wine for some time to obtain the desired aromatic and stabilizing effects. It is much cheaper and more efficient to use alternatives however, the degree of evaporation will not be in the same extent as that of an oak vessel and, in some cases, the resulting effect on concentration might be the main difference in style and in quality between oak vessels and alternatives.
The key to oak usage in winemaking is how harmonious its effect becomes in relation to the intended style of the wine. There are so many options available that it is not always possible to discern which were used. Fundamental to wine quality, is whether it enhances the final wine.
In the next issue, we will look at various techniques used to produce sparkling wines which by themselves result into very different styles and quality results.