The pleasure of drinking wine is fun and easy. Make some food. Light the candles. Turn on the music. And, open a bottle with friends for dinner or celebration and enjoy! When it comes to understanding the terms and making of that wine; however, it can be intimidating. Let’s break it all down.
You may have seen the words “sur lie” on a bottle of Chardonnay or heard the term “bâtonnage” during a wine experience at a vineyard and wondered what do these mean? Here’s an explanation of these terms and why they are important to the texture and taste of wines.
During the fermentation process, yeast transfers the sugar to alcohol and when its work is done, the yeast cells die and drop to the bottom of the tank or barrel forming a fine deposit. Over time, the yeast cells break down and release a number of different compounds back into the wine such as amino acids, mannoproteins and fatty acids.
The sediment of yeast cells that die and drop to the bottom are called lees. Winemakers sometimes like to keep some of these solids in contact with the wine as a way to extract flavor, aroma and texture. The solids can then be filtered out before bottling, or the wine can be racked, leaving the solids behind. Racking is the practice of moving wine from one container to another for aeration or clarification, leaving sediment behind.
The process of wines aging “on the lees” is known as sur lie. The amount of time that a wine stays in barrel or tank on its lees will depend upon several factors including the vintage year and winemakers taste. The effect of the lees during bottle fermentation for at least 18 months on Champagne, for example, is considerable. It adds to the bread-like and toasty notes associated with some of the greatest sparkling wines which is a result of 'sur lie' aging.
Another technique is to stir the lees in the barrel. A winemaker can use a specially designed tool which is a long stick that fits into the top hole of the barrel or there are barrels designed to be rolled or rotated to upend the settled lees. This is known as bâtonnage, a French term which simply means stirring the lees. The lees are stirred using a special tool that can reach even the most inaccessible parts of the barrel, and in doing so, it redistributes the sediment among the wine, maximizing contact with the dead yeast cells. These compounds give complexity to the wine and contribute to the ‘mouthfeel’ or weight of the wine and to its distinctive aromas and flavors. In the case of great Chardonnay, such as Montrachet, bâtonnage adds a toasty, nutty quality and additional depth and complexity.
Oftentimes, the process chemically alters the oak flavor molecules from the barrel increasing the integration of the wine, and making the oak seem less obtrusive to the palate. This is desirable because oak tannins are a polyphenolic acid and can be harsh to the taste.
The importance of using this technique is that if left alone, the yeast solids settle to the bottom of a barrel. If the lees are left undisturbed, they run the risk of stinky hydrogen sulfide forming. Bâtonnage helps prevent this, as well as extract some of the texture and complexity the lees can offer. On the other hand, if a winemaker keeps stirring the lees endlessly the stirring will eventually make the wines taste less fresh. So there’s a bit of a balancing act.
There is an elegance and finesse to the dance of bâtonnage that warrants a deft hand and intentional mindset. It is quite an extraordinary part of the winemaker’s technique.
And so, viniculture and oenology are both science and art and a great vintner is sensitive to the chemistry and details of the process as well as attune to the style of wine in which it is being cultivated and the temperament of the grapes, terroir and region. It is a noteworthy process to be explored.