• Yeast is a single-cell fungi essential to alcoholic fermentation
• It converts the sugar in grape juice (fruit juice) into alcohol and carbon dioxide (CO2)
• There can be ambient yeast or cultured yeast
Ambient yeast
• Also known as native yeast or wild yeast, it’s found in the winery or vineyard
• Ambient yeast is peculiar to the environment where it lives (more on terroir soon)
• There can be several yeast populations in a vineyard/winery
Cultured yeast
Also known as commercial yeast or selected yeast
Lab-produced strains of yeast with specific characteristics and aromas
Can be made and sold at scale based on market needs
Yeast in Natural Wine and Winemaking
• Natural winemakers prefer not to inoculate cultured yeast
• That’s why we speak about spontaneous / wild fermentation with ambient / native yeast
• Saccharomyces cerevisiae is the most common yeast responsible for alcoholic fermentation
Sources:
https://www.vininaturali.it/fare-il-vino/vinificazione/fermentazione/
https://www.sciencedirect.com/science/article/pii/S221078431630064X
https://daily.sevenfifty.com/the-science-of-winemaking-yeasts/