Fermentation innovation – how evolution is shaping the taste of your pint
Posted on: 20 November 2019
Have you ever wondered how brewers take a handful of natural ingredients and turn them in to your favourite pint? Tastes differ and so everyone will have their own ideas about what makes a top tipple, but the ever-present micro magicians that do the hard work are yeasts.
According to a new piece of research, led by Chris Hittinger of The University of Wisconsin and including a team of scientists from Spain, Portugal, France, Argentina and also here at Trinity, the evolutionary history of yeasts that has given rise to our fermentation innovations is surprisingly complex – although a detailed genomic analysis of 122 hybrids showed their roots could be traced to between just two and four common yeast species.
Yeasts reproduce asexually (to produce clones) or sexually by mating between strains within a species. However, on rare occasions, mating can occur between different yeast species to create hybrids that contain genomic information from generally two species (although hybrids with genes from three or even four parental genomes have been found).
The hybrids most often display “hybrid vigour” as evidenced by improved characteristics not found in their parents, such as adaptations to new environmental conditions. These improvements result from the mixture of genes inherited from the different parental species.
Lager beers are produced using Saccharomyces pastorianus, a hybrid of Saccharomyces cerevisiae, the common or garden variety of baker’s yeasts and its more exotic cousin Saccharomyces eubayanus, a species originally found in Patagonia, South America and laterally found in China, Tibet and the USA.
This hybrid combines the excellent fermentation capacity of S. cerevisiae and the cold tolerance of S. eubayanus, making it possible to brew lagers at cold temperatures. This creates a crisp, fresh beer with hints of rose, citrus or other fruity flavours as well as bitterness from the hops that are adding during brewing.
The flavours in a beer depend on the mixture of genes in the hybrids. So, understanding how these strains evolved and what flavour genes they carry will be of benefit to the brewing industry and to craft brewers as they search for the perfect flavour palette.
- Of the 122 yeast hybrids analysed, 105 (86%) had their origins traced to industrial settings; these came from beer, wine, cider, distilleries or other beverages
- Many genes that contribute to distinct flavours are present in yeasts used to brew niche beers (e.g. clove-like, smoky, Trappist-style beers)
- Some genes that produce what are considered “off-flavours” have been lost in lager yeasts.
- There have been multiple, complex hybridisation events between different yeasts but brewing processes (influenced by consumer tastes) have exerted strong selective pressures on yeast evolution
Ursula Bond, Associate Professor in Microbiology at Trinity College Dublin, is one of the authors of the research article that has just been published in leading international journal, Nature Ecology & Evolution.
Professor Bond said:
Hundreds of years ago one strain of yeast met another and sparked the cold-brewing revolution that led to crisp, refreshing lagers taking over the global beer market.
Our analyses paint a detailed picture of the surprisingly complex world of yeast evolution – much of which has been driven by fermentation innovation and our curiosity for producing a pint for all seasons.
Professor Bond is currently leading a Horizon 2020-funded project entitled Aromagenesis,which aims to use our growing knowledge of yeast genetics to create new flavours (and healthier versions) of beer and wine.
Thomas Deane, Media Relations Officer | email@example.com | +353 1 896 4685