Wort fermentation and beer conditioning with selected non-Saccharomyces yeasts in craft beers

Abstract

The use of non-Saccharomyces yeasts means a great source of biodiversity for the production of differentiated beer products. With this objective, five species of different genera have been selected in order to evaluate their influence on beer quality. Two different experiments were carried out with four non-Saccharomyces strains (Schizosaccharomyces pombe, Torulaspora delbrueckii, Saccharomycodes ludwigii and Lachancea thermotolerans) and Saccharomyces cerevisiae, as control. In the first experimental setup, the five strains were used to carry out the pure culture wort fermentation and to undertake bottle conditioning. In a second experimental setup, the wort was fermented with S. cerevisiae and the four non-Saccharomyces strains were used for bottle conditioning. Beers from the first experimental setup had low ethanol content due to the wort’s original gravity; T. delbrueckii produced a beer with the largest quantity of isoamyl acetate. In the second setup, the wort had higher original gravity; most of the fermentative volatiles were produced in larger amounts (1-propanol, isobutanol, 2-methyl-1-butanol, 3-methyl-1-butanol) with all tested strains. The differences observed in the volatiles production were more pronounced when the yeast strains were used for the fermentation and the bottle conditioning than whey they were used just for the bottle conditioning. The species S. pombe produced a significantly higher ethanol concentration (%v/v) in both experimental setups; these beers also obtained the highest scores for the sensory attributes foam consistency and foam persistence. Beers produced with T. delbrueckii and S. ludwigii had low ethanol content in both experimental designs, in pure culture fermentation and in bottle conditioning.