🍷 Fermentation

Fermentation is the work of yeast or bacteria. They turn sugar into other substances: alcohol or acid.

This is how wine is made. Grape juice contains sugar. Yeast eats it and releases alcohol and carbon dioxide. This is alcoholic fermentation. It can happen on its own, with wild yeast from the grape skins, or be started with added yeast. After it, wine sometimes goes through malolactic fermentation, where bacteria turn sharp malic acid into softer lactic acid.

People have used fermentation for a long time. One of the earliest known fermented drinks was found at Jiahu in China and is about nine thousand years old. Fermentation also matters in dairy: a starter culture begins it in milk and gives fermented milk products. Without fermentation there would be no wine, beer, yoghurt or kefir.