Screening for the Brewing Ability of Different Non-Saccharomyces Yeasts

Yvonne Methner,Fritz Jacob,Mathias Hutzler,Maximilian Michel,Dagmar Matoulková

doi:10.3390/fermentation5040101

Yvonne Methner, Fritz Jacob + Show 3 more

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https://doi.org/10.3390/fermentation5040101

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Abstract

Non-Saccharomyces yeasts have aroused interest in brewing science as an innovative and seminal way of creating new beer flavors. A screening system for potential brewing strains of non-Saccharomyces yeasts was set up to investigate the yeast’s utilization of wort sugars and to examine the effect of hop acids as well as ethanol on the growth of different yeast strains. Additionally, phenolic off-flavor (POF) and sensory odor tests of fermented wort samples were performed. The promising strains were further investigated for their propagation ability and for following fermentation trials. The produced beers were analyzed for secondary metabolites, ethanol content and judged by trained panelists. Subsequently to the screening, it was discovered that among the 110 screened yeast strains, approx. 10 strains of the species Saccharomycopsis fibuligera, Schizosaccharomyces pombe and Zygosaccharomyces rouxii generate promising fruity flavors during fermentation and were able to metabolize maltose and maltotriose as a prerequisite for the production of alcoholic beers. Consequently, the screening method described in this study makes it possible to investigate a tremendous number of different non-Saccharomyces yeasts and to test their brewing ability in a relatively short period of time.

Highlights

Known to most brewers as spoilage yeasts or as co-fermenters in mixed fermentations, non-Saccharomyces yeasts have received very little attention since the introduction of what are referred to as high-performance Saccharomyces brewing yeasts [1,2]
phenolic off-flavor (POF) and odor tests were taken into consideration as the aim of this study was to identify yeast strains that are able to produce pleasant novel flavors during the wort fermentation, excluding POF positive yeast strains
Non-alcoholic beers are as promising as those with an average alcohol content, this study first focused on the yeasts strains which are able to metabolize maltose to produce a standard or at least an alcohol-reduced beer

Summary

Introduction

Known to most brewers as spoilage yeasts or as co-fermenters in mixed fermentations, non-Saccharomyces yeasts have received very little attention since the introduction of what are referred to as high-performance Saccharomyces brewing yeasts [1,2]. Michel et al [4] and Basso et al [5] emphasized the great potential of non-Saccharomyces yeasts to develop beers with different alcohol contents and a broad range of flavors. They highlighted the varying abilities of unconventional yeasts to metabolize desirable aroma-active substances such as fruity esters, monoterpenes, higher alcohols, phenols and acids. The fermentation ability of brewer’s wort carbohydrates was discussed with the resulting alcohol content. Both reviews were, amongst others, focusing on species such as Torulaspora delbrueckii, Dekkera/Brettanomyces and Pichia kluyveri

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