What is the term for natural fermentation initiated by wild yeast?

Spontaneous fermentation refers to the natural process where wild yeast present in the environment start the fermentation without the need for any added cultured yeast. This method relies on the indigenous microorganisms that exist on the grapes, in the winery, and even in the air.

When grapes are harvested, they carry a variety of wild yeast strains. During spontaneous fermentation, these yeasts convert the sugars in the grape juice into alcohol and carbon dioxide. This type of fermentation can lead to distinct flavor profiles in the wine, as the wild yeasts bring a complexity and variety that controlled methods may not achieve.

Controlled fermentation, on the other hand, typically employs specific yeast strains that are added to the must to ensure a predictable fermentation process. Malolactic fermentation is a secondary fermentation process primarily involving the transformation of malic acid into lactic acid, which occurs after primary fermentation and is mostly associated with certain red wines and some whites. Inoculated fermentation also involves the addition of cultured yeast to begin fermentation, which differs significantly from the natural processes highlighted in spontaneous fermentation.