Did you know there are actually two types of lees? Not only are there different kinds, but they are actually quite different from one another.
One kind of lees can spoil your wine in a very short time. The other kind has the potential to take a good wine and make it great by adding flavor compounds as well as smoothing out the mouthfeel.
The gross lees refers not to how disgusting the stuff may be but the size of the debris. When you make wine from fresh fruit it is inevitable that some of the grape skins, seeds, and perhaps a stray stem or two will wind up in the bottom of your fermentation container.
It’s this chunky style lees that causes the most concern when it comes to determining how long you can let your wine sit before racking. The gross lees that can leave really funky flavors in your wine in short periods of time.
As the pile of grape leftovers decomposes it can produce some rather offensive compounds. The gross lees may have spoilage organisms, sulfur, or excess sulfur dioxide left over from the vineyard.
On the other hand there is the fine lees. That’s the silky sediment that gently piles up on the bottom of your carboy. This is the stuff that gets stirred up so easily when racking your wine. Primarily the fine lees is comprised of dead yeast cells.
As these cells break down they contribute primarily polysaccharides (long carbohydrates) and mannoproteins. Additionally they can bring out flavors of nuts, honey, bread, etc. The proteins can bind with tannins and help smooth out the wine.
Sur Lie Aging
Aging wine on the lees for a controlled period of time is often done to pick up interesting flavors from the yeast. However, you should know that when wine makers age their wines “on the lees” they are referring to the fine lees. This is a seldom made but pertinent distinction.
For more information on this subject check out Sur Lie Aging Explained.
You can keep your wine on the gross lees for a period of a couple weeks and be okay. However, you can leave your wine on the fine lees for much much longer periods of time.
Further different strains of yeast will impart different flavors on your wine as they decompose as they did during fermentation (here’s a bit more about the affects of different yeast strains of the flavor of wine). So be sure to do your research on sur lie aging and your particular strain of yeast. Check back for more on sur lie aging soon!
Photograph of gross lees by: Vagabond Shutterbug