What does Spontaneous fermentation mean?

Spontaneous fermentation means the wine was fermented by the wild yeasts found naturally on the grapes and in the cellar, not by added cultured yeast.

Also known as: Wild yeast, Native yeast, Indigenous yeast

Spontaneous fermentation means fermentation starts on its own with the wild yeasts found naturally on the grape skins, in the vineyard and in the winery. The producer does not add cultured yeast, which is otherwise standard in modern winemaking.

During a spontaneous fermentation several yeast species work in turn. At first, species with low tolerance to alcohol dominate, and gradually Saccharomyces cerevisiae, the true wine yeast, takes over and finishes the job. Fermentation often starts more slowly and can take longer than with cultured yeast.

Many producers believe spontaneous fermentation gives more complex wines with a stronger link to the place, since the yeast population differs between vineyards and cellars. The method is also harder to control. Fermentation can stop before all the sugar is used, and the risk of unwanted notes such as volatile acidity is higher, which calls for healthy grapes and close monitoring.

Spontaneous fermentation is standard in natural wine and common among many traditional producers, especially in Bourgogne and Germany. Cultured yeast gives predictability, but which method is used says more about style than about quality.