In a study appearing online in the journal Genome Research, scientists from Stanford University in California say they have been able to identify the origins of Saccharomyces pastorianus yeast, a ‘hybrid’ organism used in lager.
Such a breakthrough may help scientists and brewers to better understand how to manipulate the individual yeast strains that contribute to taste, colour and even aroma variation in lagers, the report states.
The research looked at the two components of S. pastorianus, S. bayanus and S. cerevisiae, particularly in their ability to ‘out-compete’ other yeasts during the cold fermentation process of lager.
To better understand the organisms’ affects on lager composition, the researchers compared the various genomic properties of yeast strains used at different breweries around the globe.
As part of this testing, Dr. Barbara Dunn and Dr. Gavin Sherlock said they had attempted to measure the contribution of the two parent yeasts in strains of S. pastorianus. The study is said to have found new insights into how the use of yeast had evolved in lager production.
Dunn said that the findings indicated that two distinct groups of S. pastorianus exist, although major genetic variations were found even within these two divisions. She added that the discovery indicated a flexibility in the uses of yeast for the production of beer.
"The fact that lager yeasts isolated from different breweries each seem to have a unique genomic make-up may indicate that the yeasts are adapting to the conditions specific to each brewery," Dunn stated.
"Our discovery that unique genomic structures may be characteristic to each brewery and/or beer type could lead to insights on how to directly control flavour and aroma in beer."
Despite its many traditions, lager making remains a relatively new development in drink manufacture, having only gained worldwide acceptance in the late 19th century, according to the researchers.
By comparison, ale-type beers have been brewed for thousands of years using the S. cerevisiae yeast also favoured by bakers.
The report states that the difference in yeasts used between the two beer varieties allows lager products to undergo fermentation at a much lower temperature.
Source: Genome ResearchPublished online, doi:10.1101/gr.076075.108." Reconstruction of the genome origins and evolution of the hybrid lager yeast"Authors: B. Dunn and G. Sherlock