The influence of Torulaspora delbrueckii on beer fermentation.

In this study, the effect of five different Torulaspora delbrueckii strains in combination with an ale type Saccharomyces cerevisiae on physical, chemical, microbiological, aroma composition, and sensory profiles of beer were examined. The ethyl alcohol content of produced beers ranged from 5.46% (v/v) to 5.93% (v/v), while the highest alcohol amount was obtained using a pure culture of S. cerevisiae. The major volatiles among beer aroma compounds was acetaldehyde, n-propanol, 3-methyl-butanol, 2-methyl-butanol, ethyl acetate, isoamyl acetate, 2,3-butanedione, and 2,3-pentanedione. It was ascertained that the total amount of higher alcohols was higher in the S. cerevisiae control beer compared to all mixed fermentations. Total ester levels were higher in all the mixed culture beers than the control beer. Sensory evaluation showed that all the mixed cultures of S. cerevisiae and T. delbrueckii positively influenced the sensory profile of the beers. Strain Y1031 was the most preferred and was characterized as rich in hop aroma and full bodied. It is therefore a suitable strategy to use T. delbrueckii in mixed fermentations with S. cerevisiae to produce beer with a distinctive flavor. The results demonstrate that, T. delbrueckii strains isolated or commercialized for winemaking can be equally employed as well in brewing.