Chapter 5

Yeast and Winemaking

Yeast Role in Wine Production

The primary role of yeast during alcoholic fermentation is to convert most of the glucose and fructose present into alcohol and carbon dioxide. While the production of alcohol is the most noteworthy by-product of yeast metabolism from a winemaking perspective, there are several other by-products that yeast produce that can be also influence the resulting wine. This includes glycerol which contributes increased body and a slightly sweet taste without increasing the alcohol level of the wine. Other by-products of yeast include: methanol, fusel alcohols, succinic acid, acetic acid, acetaldehyde, hydrogen sulfide, pyruvic acid, and various esters, ketones, lactones, phenols, acetals so name a few.

Life Cycle of Yeasts

The life cycle of the yeast Saccharomyces cerevisiae during fermentations generally shows a growth pattern consisting of four phases - lag, log, stationary, and death.

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