The effects of mixed culture of Saccharomyces cerevisiae and Torulaspora delbrueckii on ethyl alcohol fermantation in beer production

In the present work, the effects of adding 5 different Torulaspora delbrueckii strains along with the lager type Saccharomyces cerevisiae in mixed culture for the production of beer were investigated on physical, chemical, microbiological and sensory properties of beer and thus quality. Fermentation was completed on the 12th day and the green beer was transferred and maturated at 4 °C for approximately 1.5 months. According to the data obtained; the highest total yeast count was measured in T.delbrueckii C134V4 and Y1013 trials (6.84 log cfu/mL). Moreover, the lowest non-Saccharomyces spp. yeast count was measured in T. delbrueckii Y1018 trial while the highest was in T. delbrueckii C134V4. The specific gravity in beers was obtained in the range of 1,006-1,007 gr/cm3. The amount of ethanol content varied from 5,46% to 5,93% (v/v). It was found that in all mixed culture samples, the total amount of higher alcohols and esters were significantly higher than that of control sample. The highest amount of acetaldehyde, 2-methylbutanol, ethyl acetate and isoamyl alcohol was observed in the beer produced with T.delbrueckii Y1018 strain. According to the results of sensory evaluation, beer sample produced with mixed culture of S. cerevisiae and T. delbrueckii Y1031 was found to be high in hop aroma and full-bodied and it was the most preferred trial by the panelists. In conclusion, it was determined that the use of T. delbrueckii, a non-conventional yeast, in mixed culture fermentations with S.cerevisiae was effective on beer quality.