Abstract
Flavor stability is important for beer quality and extensive efforts have been undertaken to improve this. In our previous work, we proved a concept whereby metabolic engineering lager yeast with increased cellular nicotinamide adenine dinucleotide hydride (NADH) availability could enhance the flavor stability of beer. However, the method for breeding non-genetically modified strains with higher NADH levels remains unsolved. In the current study, we reported a novel approach to develop such strains based on atmospheric and room temperature plasma (ARTP) mutagenesis coupled with 2,4-dinitrophenol (DNP) selection. As a result, we obtained a serial of strains with higher NADH levels as well as improved flavor stability. For screening an optimal strain with industrial application potential, we examined the other fermentation characteristics of the mutants and ultimately obtained the optimal strain, YDR-63. The overall fermentation performance of the strain YDR-63 in pilot-scale fermentation was similar to that of the parental strain YJ-002, but the acetaldehyde production was decreased by 53.7% and the resistance staling value of beer was improved by 99.8%. The forced beer aging assay further demonstrated that the favor stability was indeed improved as the contents of 5-hydroxymethylfurfural in YDR-63 was less than that in YJ-002 and the sensory notes of staling was weaker in YDR-63. We also employed this novel approach to another industrial strain, M14, and succeeded in improving its flavor stability. All the findings demonstrated the efficiency and versatility of this new approach in developing strains with improved flavor stability for the beer industry.
Highlights
Flavor is the main quality characteristic for beer and requires the flavor-active components presented as raw materials or developed by yeast metabolism to be controlled within a certain range in order to maintain flavor balance [1,2,3]
Three runs of ARTP mutagenesis were performed on strain YJ-002 and 172 colonies were obtained from the Yeast extract Peptone Dextrose (YPD) agar plate containing 0.10 mM DNP
After 10 days treatment, we found that levels of the aging indicator 5-HMF in YJ-002 samples was 1.57-fold than that of the 5-HMF levels in YDR-63 samples (Figure 5b), strongly indicating that the staling degree of beer caused by YJ-002 was much higher than that caused by YDR-63
Summary
Flavor is the main quality characteristic for beer and requires the flavor-active components presented as raw materials or developed by yeast metabolism to be controlled within a certain range in order to maintain flavor balance [1,2,3] For many breweries, this issue can be addressed through good manufacturing practices. Improving the flavor stability of beer during its shelf life is of great concern for brewers as it is important for a commercial beer to have a consistent sensory experience and satisfy the expectations of consumers at all times Aldehydes such as (E)-2-nonenal, 5-hydroxymethylfurfural, hexanal, and acetaldehyde are characterized as the aged flavor components in beer, and higher concentrations of these aldehydes greatly impair flavor stability [7,8,9]. We proposed that higher reducing activity could be directly replaced by the higher reducing nicotinamide adenine dinucleotide hydride (NADH) level in yeast, and confirmed that increasing cellular
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
