Yeast is the microorganism that ferments grape sugar into alcohol and carbon dioxide, making wine possible. Winemakers either rely on wild (native) yeasts present on grapes and in the cellar, or add a cultured commercial strain for a faster, more predictable fermentation. Yeast choice affects aroma, texture and reliability, and spent yeast cells (lees) add flavour and body through autolysis during aging.
WHY IT MATTERS FOR COLLECTORS
Yeast is a quiet but pivotal variable: native-yeast fermentations are prized for complexity and terroir, cultured strains for consistency. Lees contact from spent yeast builds the creamy texture and bready notes of fine whites and sparkling wines.
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