 Humans have used fermentation to produce foodstuffs and beverages since the Neolithic age.For example, fermentation is used for preservation in a process that produces lactic acid found in such sour foods as pickled cucumbers, kombucha, kimchi, and yogurt, as well as for producing alcoholic beverages such as wine and beer.Fermentation also occurs within the gastrointestinal tracts of all animals, including humans.