Alcoholic fermentation is the process during which sugars from the grapes are converted into alcohol by the yeasts. This process also produces flavor compounds, heat, and carbon dioxide.
The yeasts are microscopic fungi that convert sugar into alcohol during winemaking and affect the aromas of the wine. A winemaker can use cultured yeast strains selected in laboratory or ambient yeast that are present in the vineyard and the winery. Cultured yeasts are known to produce reliable fast fermentation and help to produce consistent product overt time. Ambient yeasts can add complexity because of the number of species producing different aroma compounds. It is also known that the dominant yeast population in a must is unique to a place or region, contributing to the idea of terroir of the wine.
In Geneva, they are several producers using ambient yeasts. To discover them, join the club!