Glossary entries

The microscopic, single-celled fungi that are the driving force of fermentation. Once in contact with grape juice, an enzyme within yeast begins converting the natural sugar in grape juice into alcohol and CO2. Yeasts are airborne, particulary in and around vineyards and cellars. These natural yeasts are known as ambient, indigenous or wild yeasts. Alternatively, many winemakers prefer to inoculate the grape juice with cultured yeasts, which “perform” with greater predictability and dependability.