Why do we use yeast in wine or beer?

Without yeast there is no wine or beer. During winemaking or brewing fermentation, yeast converts sugars from grapes or the brew into alcohol. Yeast, through their metabolic activities, then render non-aromatic compounds into odorous and volatile ones that help define the style and signature. Oenologists, brewers and microbiologists carefully select specific yeasts from nature based on specific criteria to optimize wine and beer quality.