Aroma compounds profile is affected by the initial yeast ratio in wort co-fermentations

Abstract

In recent years, the boom of the craft beer industry refocused the biotech interest from ethanol production to diversification of beer aroma profiles. This study analyses the fermentative phenotype of a collection of non-conventional yeasts and examines their role in creating new flavours, particularly through co-fermentation with industrialSaccharomyces cerevisiae. High-throughput solid and liquid media fitness screening compared the ability of eightSaccharomycesand four non-Saccharomycesyeast strains to grow in wort. We determined the volatile profile of these yeast strains and found thatHanseniaspora vineaedisplayed a particularly high production of the desirable aroma compounds ethyl acetate and 2-phenethyl acetate. Given thatH. vineaeon its own was a poor fermenter, we carried out mixed wort co-fermentations with aS. cerevisiaebrewing strain at different ratios. The two yeast strains were able to co-exist throughout the experiment, regardless of their initial inoculum, and the increase in the production of the esters observed in theH. vineaemonoculture was maintained, alongside with a high ethanol production. Moreover, different inoculum ratios yielded different aroma profiles: the 50/50S. cerevisiae/H. vineaeratio produced a more balanced profile, while the 10/90 ratio generated stronger floral aromas. Our findings show the potential of using different yeasts and different inoculum combinations to tailor the final aroma, thus offering new possibilities for a broader range of beer flavours and styles.