Autolysis

Autolysis is the name for the process whereby spent yeast cells decompose. When a wine is left sur lie, or “on the lees,” it remains in contact with the yeasts (now dead) that performed the fermentation. As the yeasts’ cell walls collapse, enzymes start to break down the cells themselves, releasing polysaccharides, amino acids, and other compounds into the wine. These impart an extra dimension of yeasty, biscuity flavor, plus a creamy texture, the perception of a fuller body, and greater complexity. The effects of autolysis are very apparent in Champagnes and sparkling wines that have been left on their lees, sometimes for many years, after a second fermentation in the bottle and before the wine is disgorged, removing the spent yeasts.