Yeast Strains and Wort Color as Factors Affecting Effects of the Ethanol Fermentation Process

Dark malts used in the production of brewing wort affect the ethanol fermentation process, the phenolic content, antioxidant capacity and the physiology of yeast cells. An innovative element of this research is the combination of investigating the effect of beer wort color modulated by the use of dark specialty malts on the course and effects of fermentation and the characteristics of post-fermentation yeast biomass of brewer's strains with different characteristics. Dark and pale beer were obtained. The beers had different ethanol contents (4.51-5.79% v/v), resulting from real (62.29-80.36%) and apparent (75.37-98.26%) attenuation levels. Metabolic and morphological differences were demonstrated in the brewer's yeast strains used. S. cerevisiae var. diastaticus was distinguished by its ability to ferment dextrin, resulting in the highest ethanol content in beers. The total phenolic content in beer depends on the color of the wort and the yeast strain used (244.48-547.56 mg of gallic acid/L). Dark beers show higher ferric ion reduction ability (FRAP) and antioxidant capacity (ABTS^•+) than pale beers fermented with the same yeast strains. Through biomass analysis, differences in yeast cell physiology depending on yeast strain and beer wort color were also revealed.