Wines aged sur lie (French for "on the lees") are kept in contact with the dead yeast cells and are not racked or otherwise filtered. This is mainly done for whites, to enrich them. (It is a normal part of fermenting red wine, and so is not noted.) The concept originated in Burgundy, with Chardonnay, but is now popular around the world with numerous white grape varieties. Sur lie aging can be overdone, leading to an off-putting leesy flavor.