A group of Belgian researchers has discovered that the yeast used to brew beer today started its life more than 500 years ago, and it’s our love of the frothy beverage that shaped the microbe’s genetic history.
Yeast is one of the main ingredients of beer and is considered the “motor” of the drink — yeast cells eat the sugars from barley and other ingredients, and convert it to alcohol and carbon dioxide.
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Dr. Kevin Verstrepen, a professor of genetics at the University of Leuven and the Flanders Institute of Biotechnology in Belgium, spoke about his research to Quirks Quarks host Bob McDonald. You can listen to the full program when it airs this weekend on CBC Radio One.
He said many breweries have their own yeast strains, and they closely guard them — that’s what makes their beer distinctive. But the researchers said many brewers don’t know where their strains come from.
His team wanted to unravel this mysterious genetic history.
By comparing the DNA sequences of hundreds of yeast strains, they found that beer yeast is completely different from wild yeast. Verstrepen says that separation “from their feral brothers and sisters” happened in the 1500s and 1600s.
That’s around when beer brewing became more professional, he said. In order to keep their beers consistent, brewers would use the sediments left over from one batch of beer for the next. They also found that re-using this sediment sped up the fermentation process for the next batch.
This sediment was actually yeast.
“They started really taking a population of yeast and only having that population live in the brewery. So the population eventually started adapting to their new environment and that yeast became expert brewing yeast, if you will,” he said.
This process was essentially selective breeding for yeast, similar to what farmers did with cattle.
“There it’s maybe more obvious — if you have a cow that gives lots of milk, well maybe you want to breed it and hopefully some of the offspring will also produce lots of milk,” Verstrepen said. “So the brewers were doing something similar without really realizing it.”
Brewers were choosing yeast strains for the particular aromas they gave their brews.
Verstrepen said the oldest strains of beer yeast are from Belgium, Germany and the Czech Republic. He said there is a clear split from yeast found in U.K. beers.
“And then from that, in the 1620s or so, you see the U.S. yeast. So some of the early settlers from the U.K. must have taken some yeast with them and figured that they also wanted to make some beer in America.”
Verstrepen said the beers back then would likely have tasted more acidic, but less bitter, than today’s. And many brewers did not use hops, a common ingredient in modern beer.