Lees

Lees are the sediment that settles at the bottom of fermentation vats and storage tanks or barrels while the wine is being made. In French and in technical language you will often come across the word lies. Lees consist mainly of spent yeast cells, which sink to the bottom once they have converted the sugar in the grape juice into alcohol, but also of small pieces of grape skin, seeds and other solid particles from the must. So they are a perfectly natural by-product of fermentation, not a sign of a fault.

For you as a drinker, lees matter because some winemakers deliberately let the wine rest on its own sediment for a period. As the yeast cells slowly break down, they release substances that can give the wine more body, a creamy texture and aromas reminiscent of bread or yeast dough. This is called ageing on the lees or sur lie, and you will find it in many mousserende vine and in certain white wines, among others. Other wines are instead drawn off the lees early to keep them fresh and clean in flavour.

A widespread misunderstanding is that sediment in the bottle is lees. The cloudy matter you sometimes see in a mature red wine is most often colour and tannin compounds that have clumped together. Lees belong primarily in the cellar, before the wine is finished, where they are either removed or used actively by the winemaker.