What is “spontaneous fermentation”?

The Lugana that’s produced from grapes on the Sansonina estate is labeled fermentazione spontanea or spontaneous fermentation in English.

That means that the wine has not been “inoculated” with “cultured yeast” or “select yeast” as it is sometimes called.

Fermentation is the process by which sugar is converted to alcohol by yeast. The microorganisms consume the sugar and one of the byproducts of their feast is alcohol.

Across the world today, the overwhelming majority of the wines produced are made by adding a cultured or lab-grown yeast to the grape must to provoke fermentation. (Cultured yeast can also be called “inoculated yeast.”)

That’s not a bad thing. By no means.

Inoculation allows the winemaker to control the fermentation with precision.

Some winemakers use specific cultured yeast to give their wines particular flavors.

But most producers prefer neutral yeasts that don’t shape the aroma or flavor profile of the wine. A neutral yeast allows the naturally occurring yeast to do its job without the risk of unwanted yeast or or bacteria that could affect the resulting wine.

Spontaneous fermentation, also called “wild ferment” in certain circles, relies solely on the naturally occurring yeast — sometimes also called “ambient yeast” or “native yeast.”

When the Zenato family decided to make a spontaneously fermented Lugana from grapes grown on the 13 hectares of the Sansonina estate, they did so because they wanted the wine to be the purest expression of the place itself.

It’s tricky business to wild ferment your wines. But the results in this case have been spectacular.

To learn more about inoculation and yeast, see the Oxford Companion to Wine entry for “yeast” (subscribers only).

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