**4.1 Fermented food**

Melatonin concentration can range from picograms to nanograms per mL of product in fermented beverages such as wine and beer. Although the content of melatonin can vary in different unfermented products, it has been proven that the alcoholic fermentation process is important for the melatonin formation process, since it is generated after the addition of yeasts, the role of *Saccharomyces cerevisiae* being fundamental [5, 72].
