Coculturing of non-Saccharomyces cerevisiae and Saccharomyces cerevisiae for improving the aroma quality and antioxidant characteristics of beer with Yuan'an yellow tea

The utilization of mixed cultures of Saccharomyces and non-Saccharomyces cerevisiae strains to improve the quality and aroma complexity of wines has garnered considerable attention as of late. In this study, three non-S. cerevisiae strains exhibiting a strong β-glucosidase production capacity were screened from the yeasts preserved in the laboratory. Subsequently, the physiological characteristics of the strains were evaluated through growth curve analysis as well as alcohol and osmotic pressure tolerance experiments. Finally, the non-S. cerevisiae strain S14 (Torulaspora delbrueckii) was selected and applied to ferment Yuan'an yellow tea beer combined with S. cerevisiae S189. The results showed that the optimal fermentation performance was achieved when S14 was inoculated first, followed by the addition of S189 after 12 h of fermentation, with an S14:S189 ratio of 10:1. Mixed fermentation resulted in a significant increase in the concentration of volatile flavor compounds in beer, particularly terpenes, alcohols, esters, and acids, which exhibited levels of 520.98 μg/L, 5534.28 μg/L, and 1631.80 μg/L, respectively; these values were 299.25%, 32.45%, and 56.57% higher compared to purebred fermentation. Furthermore, mixed fermentation demonstrated an improvement in the antioxidant activity of beer, as evidenced by the increase in the comprehensive evaluation score (CES) from 1.86 to 2.89. Overall, these findings indicated the notable advantage of non-S. cerevisiae strain S14 in fermenting Yuan'an yellow tea beer.