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Isbell, Todd (2023) Assessment of stress tolerance and fermentation performance in traditional Norwegian Landrace (Kveik) yeast. MRes thesis, University of Nottingham.

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Abstract

Kveik yeast are believed to constitute a subspecies of Saccharomyces cerevisiae used by rural Norwegian brewers to brew traditional ales for personal and ceremonial consumption. These yeasts have remained largely unexplored until recent times, where their potential for use in mainstream beer production has been realised. Due to the nature of their origins and use, kveik cultures often comprise multiple strains, although single-strain isolates have been identified. Irrespective of their composition, the advantage of kveik yeast is that they ferment rapidly at high temperatures and, under these conditions, produce a relatively neutral flavour contribution when compared to contemporary brewers yeasts. However, a full understanding of the properties and potential for kveik strains has yet to be achieved.

This thesis aimed to investigate several aspects of kveik yeast. Firstly, the nature and strain composition of kveik slurries was explored to determine the extent of variation within a defined culture. Subsequently, the capacity of individual kveik strains to tolerate stressors present during fermentation was investigated. Based on this analysis, the fermentation performance of kveik strains was compared to contemporary brewers yeast at a range of temperatures. This was achieved through assessment of fermentation progression, as well as the development of flavour compounds. As part of this study, the contribution of individual isolates to a fermentation was assessed using various blends of kveik yeast, derived from the same 'mother' culture.

The data obtained demonstrates that kveik yeast are able to ferment successfully at high temperatures, due to their capacity to endure a range of stress factors, including a high degree of innate thermal tolerance. Furthermore, although kveik yeasts were shown to exhibit a similar capacity to attenuate wort as their contemporary brewing yeast counterparts, volatile analysis indicated that kveik strains are unique and distinct when compared to other brewing yeast strains. Individual strain analysis also suggested the possibility that specific strains may be dominant within a collective whole, potentially imparting a greater impact on the resulting beer from the perspective of both alcohol yield and flavour production.

Item Type:	Thesis (University of Nottingham only) (MRes)
Supervisors:	Powell, Chris
Keywords:	Kveik yeast, Brewers yeast, Fermentation, Flavour compounds, Yeast cultures, Brewing
Subjects:	T Technology > TP Chemical technology
Faculties/Schools:	UK Campuses > Faculty of Science > School of Biosciences
Item ID:	72087
Depositing User:	Isbell, Todd
Date Deposited:	22 Jul 2023 04:40
Last Modified:	22 Jul 2023 04:40
URI:	https://eprints.nottingham.ac.uk/id/eprint/72087

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