Exploring the potential and control of mixed fermentations in brewing.

Yeast species beyond established brewing strains of the closely related species Saccharomyces cerevisiae and Saccharomyces pastorianus have increasingly been the subject of research evaluating their performance under brewery conditions. These yeasts have the potential to efficiently produce beer with innovative organoleptic and nutritional properties, and improved shelf stability. Co-fermentation with multiple species of yeast allows for the pairing of yeast strains with complimentary features, and interactions between strains can be harnessed to the benefit of the brewer. In this project, mixed cultures consisting of commercially available (S. cerevisiae) brewing strains paired with non-conventional strains of yeast are assessed for fermentation performance, nitrogen consumption, and production of aroma-active volatiles. By screening cultures at centilitre scale in model wort, suitable candidates are identified for study in wort of varying extract strength and composition and assessed for resistance against reactive oxygen species, linked to the oxidative stability (and therefore shelf life) of beer in package. Mixed fermentation strategies offer a range of potentially advantageous outcomes that improve on single culture performance.