What the heck is "Lees"

Lees — Lees refer to the thick sediment that floats to the bottom during the wine's fermentation process. The lees consist of the dead yeast cells, grape skin and seed fragments and various grape solids that separate from the juice and go with gravity to the bottom of the barrel or fermentation tank. Winemakers will occasionally stir the lees during fermentation to conjure up additional contact with the grape juice and solids. This stirring of the lees gives more body and flavor to the final wine.Sur lie literally translates from the French as 'on lees'. 'Sur lie' wines are bottled directly from the lees without racking (a process for filtering the wine). In the case of great Chardonnay, such as Montrachet, this adds a toasty, nutty "hazelnut" quality and additional depth and complexity, especially on the finish. Chemically this can alter the oak flavor molecules increasing the integration, and making the oak seem less obtrusive to the palate. This is desirable because oak tannins are a poly-phenolic acid, and can be harsh. This process can also give an added freshness and creaminess to the wine, and improve color and clarity. Muscadet is made in this fashion. The effect of the lees during bottle fermentation for at least five years on champagne is considerable. The "bready" toasty notes associated with some of the greatest sparkling wines made are the result of 'sur lie' aging.

Beer — on lees is also sometimes made. Many of the beers offered by the Quebec, Canada based Unibroue are on lees.