What Does Spontaneous Fermentation Mean?

On natural wine labels, you'll often come across the phrase "spontaneous fermentation." It's one of the fundamental concepts in natural winemaking — and one of those that most directly shapes how a wine develops.

What fermentation actually is

Fermentation is the process by which yeasts convert the sugar in grape juice into alcohol and carbon dioxide. Without fermentation there's no wine — it's the basic biochemical process that turns grape juice into wine.

Added yeasts versus wild yeasts

Most modern winemaking triggers fermentation by adding selected, commercially produced yeast strains. These are predictable, start fermentation quickly, and give a more consistent result year after year.

Spontaneous fermentation takes a different path: the producer adds no yeast at all, and instead lets fermentation happen through the wild yeasts naturally present on the grape skins, in the vineyard and in the cellar. These yeast populations are often diverse — several different species and strains can take part in fermentation, not just a single one, as with added yeasts.

Why producers choose it

Spontaneous fermentation is less predictable. It can start more slowly, demands more attention and experience, and is more sensitive to cellar hygiene. But it's precisely this unpredictability that leads many producers who bet on minimal intervention to believe the result more authentically reflects the character of the grape, the vintage and the place the wine comes from.

Because a broader range of yeasts takes part in the process, spontaneous fermentation can also contribute to greater complexity and more layers in the wine — though the final result always depends on other factors too, such as grape ripeness, cellar temperature and the producer's experience.

Spontaneous fermentation at Vina Durcik

All of our wines — Naret, Vitovska and Teja — ferment exclusively spontaneously, without added yeasts. This isn't a marketing decision, but a continuation of the approach used on the Karst for generations before us: as little intervention as possible, so the wine can show what came about in the vineyard.

Curious how this approach connects to other elements of how we make our wines? Read What Does "Wine Without Sulfites" Mean? or discover our way of working.