In food science, fermentation is how microorganisms like yeasts or bacteria convert carbohydrates to simpler compounds (alcohol or organic acids) in the absence of oxygen. Fermentation occurs naturally but can be tightly controlled to produce specific foods and beverages.

Fermentation is a natural process that happens without human interference or intention (that’s how early civilizations ‘discovered’ wine from juice that sat out for too long). That being said, the process can be tightly controlled to produce specific foods and beverages such as kombucha, kimchi, and kefir.