What is autolysis in the context of winemaking?

Autolysis in winemaking refers to the process where yeast cells, after fermentation is complete, break down their own cellular structures through their enzymes. This process occurs particularly in sparkling wine production, where the wine undergoes secondary fermentation in the bottle. During autolysis, the yeast cells release compounds such as amino acids and polysaccharides into the wine, contributing to the flavor, texture, and complexity of the final product. The characteristics imparted by autolysis are often described as toasty, brioche, or nuttiness, enhancing the overall quality of the wine.

In contrast, fermentation of sugars is a distinct process where yeast converts sugars from the grape juice into alcohol and carbon dioxide but does not involve the post-fermentation breakdown of yeast cells. The addition of sugar to must refers to practices common in some regions and styles but does not pertain to the self-digestion of yeast cells. The conversion of malic acid to lactic acid, known as malolactic fermentation, is another fermentation process that softens the acidity of the wine but is separate from the autolysis mechanism. Thus, the focus of autolysis is specifically on the breakdown of yeast cells by their own enzymes after the initial fermentation has taken place.