🍷 Yeast

Yeasts are microscopic fungi that turn sugar into alcohol and carbon dioxide. Without them there would be no wine: it is yeast that makes wine from grape juice. The main species is Saccharomyces cerevisiae, the same one used for bread and beer.

The food for yeast is the glucose and fructose of grapes. Yeast eats sugar and releases alcohol, gas and heat. The work of yeast was described by Louis Pasteur in the 19th century. In winemaking there are wild yeasts, living on the skins of berries, and cultured yeasts, added by the winemaker. If yeast tires or gets too cold, fermentation stops and sugar stays in the wine.

Some yeasts are harmful: Brettanomyces, for example, gives wine an unpleasant smell. Flor, a film of yeast, is needed for sherry. Yeasts work not only in wine. In kumis and kefir they work together with bacteria, which is why these milk drinks are slightly alcoholic. The same goes for shubat made from camel milk.