Geez, what are Lees?
November, and December and January, while a bit more relaxed than the previous two months of harvest, are pretty busy in the wine cellar. In particular, we perform the first racking of our red barrels.
While rack or racking is a common winemaking technique, what is it? In simple terms it is pulling the ‘clean’ or less turbid wine off the top of the barrel while leaving the lees behind. This of course begs the question: Geez, what (in the heck) are lees?
This starts me off on a longish description of the advantages and disadvantages of those murky fluids that collect on the bottom of tanks, barrels and even bottles of wine that have undergone fermentations. In general lees are the inevitable compacted ‘sludge’ that we eventually need to get rid of if we are going to give you a clear wine. We can look at lees as our best friend or our worst enemy depending on the winemaker, the style of wine he or she is trying to make and the stage of the wine.
In fact, when I was at winemaking school in Davis, California, we were taught that lees were evil and that the sooner you could get the wine off the lees the better the wine would be. Lees were full of material that at best would take away from the fruit of the wine and at worst encourage off aromas and ultimately spoilage. While this overly cautious philosophy was not totally incorrect, most winemakers have rejected this notion. In fact, lees can be a highly effective tool in making a wine more complex both on the aroma and the palate in many types of wine.
First of all, what are these lees? They are largely spent yeast cells that have completed the alcoholic fermentation. When all the natural sugar is used up, the lees fall to the bottom of the vessel and start to break down. Most of them are dead, but not all. In addition to spent yeast there will be spent malolactic bacteria in the lees in those wines that undergo a malolactic fermentation. Similarly, to the yeast once the malic acid has all been converted to lactic acid, they will fall to the bottom of the vessel. It is unlikely that they contribute as much to the organoleptic (aroma, flavor and mouthfeel) properties of the wine but their impact should not be ignored. The third major component of the lees is finely divided particulate matter that came from the grapes themselves. The quality and quantity of this material varies considerably depending on many factors including the condition of the grapes when they came in.
For instance, if they were frozen, there will be a lot more grape material in the lees. In general winemakers want to limit the amount of grape material in white and rosé wines, and therefore will settle and rack of the juice before fermentation. However, many winemakers will talk about the benefits of taking some of the lighter lees when racking off the clear wine and leaving the heaviest material behind. A large amount of grape material in a wine that you are leaving for extended lees contact is generally considered undesirable, resulting in more off aromas and possibly harshness on the palate.
So, what are these lees good for? The practice of leaving the wine to age on lees can be broken down into several categories. Perhaps the most common is leaving white wines, especially Chardonnay, on the lees for extended aging. In France this is called aging “sur lie” (sir-lee) or literally “on the lees”. This practice is commonly combined with “Batonnage” (bat-on-naj) which literally means stirring with a baton; I have pictured our stainless-steel baton that we use to stir our barrels.
The combination of sur lie and Batonnage is often called Burgundian winemaking because the technique apparently originated there and is very common when making barrel fermented Chardonnay in that region.
Today it is used around the world and with other varieties as well such as barrel fermented Sauvignon Blanc and Semillon. At Brian Carter Cellars we use it in particular with the Array Chardonnay, stirring the lees on a monthly basis from the time it completes fermentation until just before it is bottled. Normally this is done for about 9 months between November and July but in the case of Nina’s Reserve we extend the process for another year giving us a full 20 months on the lees. I also like giving a portion of the Oriana and Abracadabra rosé some barrel fermentation in neutral barrels followed by sur lie and batonnage, although in this case it is only for about 5 months. We also get some benefit from leaving the stainless-steel fermented portion of Oriana and rosé on the lees for a similar period.
Another common way that lees are used is in extended aging of sparkling wine in the bottle. An important part of the complex process of producing wines using the méthode champenoise is the aging of the wine on the lees prior to riddling and disgorgement. In Champagne, this aging is required to be at least 12 months for a non-vintage and 36 months for a vintage champagne. Some houses will age their wines for over a decade giving them the greatest impact of lees aging. During the aging process the bottles are typically shaken every 6 months to help in the breakdown process and to minimize the compaction of the lees.
The third way that lees can be used is in the production of red wines where, instead of racking the wine off the lees after malolactic fermentation, the wine is simply topped up with the addition of some sulfur dioxide. It could be left this way for months to years and either stirred or left unstirred. This practice is a bit more controversial amongst winemakers. While I have tried this technique, and have seen some benefits especially in mouth feel, it has also led to some less attractive wines. In particular the production of hydrogen sulfide is a significant risk.
So why bother? What do lees contribute to the wine? Here is where I need to be careful not to get into too much complex chemistry! As the lees breakdown they contribute a variety of soluble compounds to the wine. The compounds are mostly derived from the cell walls of the yeast and can be broken down into the categories of polysaccharides (long chain sugars), amino acids (proteins) and mannoproteins which are a complex combination of both.
These compounds add weight to the palate of the wine as well as a complex array of aromas and flavors including yeasty (similar to bready), cheesy, toasty, nutty and floral. In addition to the direct organoleptic influence of lees they can have other benefits including protecting the wine from oxidation, softening the harsher effects of oak or red wine tannins and reducing the need for fining agents such as bentonite due to increased stability in the wine. One significant advantage often cited in the production of sparkling wine is the effect of the lees aging on the quality of the bubbles in the wine, making the mousse finer and more persistent.
Hopefully you learned something in the never-ending wine education. Something else to contemplate as you open that next bottle, smell, taste and enjoy!
Brian Carter, Winemaker, Brian Carter Cellars