Lees from Merlot
Lees refers to deposits of dead yeast or residual yeast and other particles that precipitate, or are carried by the action of "fining", to the bottom of a vat of wine after fermentation and aging. The yeast deposits in beer brewing are known as trub. However, yeast deposits from secondary fermentation of wine of both wine and beer are referred to as lees.
Normally the wine is transferred to another container (racking), leaving this sediment behind. Some wines (notably Chardonnay, Champagne and Muscadet) are sometimes aged for a time on the lees (a process known as sur lie), leading to a distinctive yeasty aroma and taste. The lees may be stirred (bâtonage in French) in order to promote uptake of the lees flavour.
The lees are an important component in the making of Ripasso where the left-over lees from Amarone are used to impart more flavour and colour to partially aged Valpolicella.
Sur lie literally translates from 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 flavour molecules increasing the integration, and making the oak seem less obtrusive to the palate. This is desirable because oak tannins are a polyphenolic acid, and can be harsh. This process can also give an added freshness and creaminess to the wine, and improve colour and clarity. <citation needed> 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' ageing.
Beer on lees (trub) is also sometimes made. Many of the beers offered by the Quebec, Canada based Unibroue are on lees.
Light lees protocol
A process in which yeast is added to wine that has completed primary fermentation. This secondary yeast addition typically remains in the wine from two to eight weeks, depending on the wine maker's goals. The yeast is stirred (bâtonage) frequently during the protocol, and racked off when the protocol is complete. Also known as secondary autolysis, a light lees protocol releases additional mannoproteins and polysaccharides that can influence the flavour and mouth feel of the wine.
- ^ see The Oxford Companion to Wine, 3rd Edition by Jancis Robinson