Abstract
Consumers require high-quality beers with specific enhanced flavor profiles and non-conventional yeasts could represent a large source of bioflavoring diversity to obtain new beer styles. In this work, we investigated the use of three different non-conventional yeasts belonging to Lachancea thermotolerans, Wickerhamomyces anomalus, and Zygotorulaspora florentina species in pure and mixed fermentation with the Saccharomyces cerevisiae commercial starter US-05. All three non-conventional yeasts were competitive in co-cultures with the S. cerevisiae, and they dominated fermentations with 1:20 ratio (S. cerevisiae/non-conventional yeasts ratios). Pure non-conventional yeasts and co-cultures affected significantly the beer aroma. A general reduction in acetaldehyde content in all mixed fermentations was found. L. thermotolerans and Z. florentina in mixed and W. anomalus in pure cultures increased higher alcohols. L. thermotolerans led to a large reduction in pH value, producing, in pure culture, a large amount of lactic acid (1.83 g/L) while showing an enhancement of ethyl butyrate and ethyl acetate in all pure and mixed fermentations. W. anomalus decreased the main aroma compounds in comparison with the S. cerevisiae but showed a significant increase in ethyl butyrate and ethyl acetate. Beers produced with Z. florentina were characterized by an increase in the isoamyl acetate and α-terpineol content.
Highlights
In the brewing industry, Saccharomyces cerevisiae and Saccharomyces pastorianus are the most used yeast species in starter cultures ensuring certain advantages in the fermentation process and in the standard product quality
We investigated the use of three different non-conventional yeasts belonging to Lachancea thermotolerans, Wickerhamomyces anomalus, and Zygotorulaspora florentina species in pure and mixed fermentation with the Saccharomyces cerevisiae commercial starter US-05
After a preliminary screening of yeasts from the Collection of the Department of Life and Environmental Sciences (DiSVA), we evaluated the use of selected strains of L. thermotolerans, W. anomalus, and Zygotorulaspora florentina in pure and in mixed fermentation at different inoculation ratios with S. cerevisiae in the brewing process
Summary
Saccharomyces cerevisiae and Saccharomyces pastorianus are the most used yeast species in starter cultures ensuring certain advantages in the fermentation process and in the standard product quality. In the past few years, brewers have payed attention to yeast selection for their fermentation efficiency and technological advantages and for the aromatic characters and the flavors they give to the final product To this end, recent genetic investigations have focused on methods to enhance the fermentation efficiency and aromatic profile of selected S. cerevisiae strains [1,2,3]. Beers produced with pure cultures of T. delbrueckii were characterized by a low alcohol content (2.66% v/v) but at the same time with distinctive analytical and aromatic profile [7,14] Lachancea termotholerans, another non-conventional yeast species, was proposed by Domizio et al [15] to produce sour beers without the use of lactic acid bacteria. Yeasts belonging to Cyberlindnera fabianii, Pichia kudriavzevii, and Pichia kluyverii were evaluated to tailor the aroma production and the ethanol content in beer [16,17]
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