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As frequent pub-goers will be well aware, there are two types of beer – lagers and ales. Lagers are brewed at cold temperatures and generally have a crisp flavour. Ales, which are considered spicy and malty, are brewed in the heat. Both get their distinctive flavour from fermentation – the conversion of sugars into alcohol and carbon dioxide – by unicellular fungi called yeast.
Adding different yeast strains to the same sweet yeast would produce different flavours of beer. Yet lager enthusiasts have been fooled – there are only 85 strains of lager yeast, compared with 358 strains for ale. If the team led by Jennifer Molinet and Francisco Cubillos at the University of Santiago in Chile has their way, new types of lager could soon be on the way, with aromas and flavours completely different from anything currently available.
Lager yeasts are hybrids, a combination of Saccharomyces cerevisiae and Saccharomyces eubayanus. S. cerevisiae is an old favourite of brewers and bakers – it’s a key ingredient in wine and bread as well as beer. S. eubayanus is more specialized, thriving in cooler environments.
Strains of S. eubayanus and S. cerevisiae were first crossed somewhere in Germany more than 400 years ago. Since then, lager yeasts have been carefully bred and selected to maximize their flavor, fermentation speed, and stability. All existing lager strains to date are derived from this original hybrid, and belong to one of just two genetically distinct groups, Saaz and Frohberg, named after a Czech town and a German brewery, respectively.
For centuries these have been considered the limits of the lager universe. But in a paper in PLOS Genetics, Dr. Molinet, Dr. Cubillos and their colleagues unveil new hybrids of S. cerevisiae and S. eubayanus. Creating such hybrids was impossible before 2011, says Dr. Cubillos. That was when a different team of researchers discovered new strains of S. eubayanus in the bark of southern beech trees in Patagonia. Dr. Molinet’s interest was first sparked by the yeast’s ability to survive the cold, harsh climate of Tierra del Fuego, the southernmost tip of the region. Only later did he set about creating new lager hybrids.
The first hybrid that Dr. Molinet and his colleagues created in 2021 failed. It was no better at converting sugars into alcohol than its parent strain. This was no surprise – today’s top lager yeasts have had the benefit of centuries of careful breeding. Undeterred, the researchers artificially sped up evolution. Over the next seven months, the team created hundreds of generations of lager yeast, each time selecting those with the most desirable properties to produce delicious brews. They soon noticed that yeasts that inherited mitochondria (the energy-producing part of cells) from S. eubayanus rather than S. cerevisiae performed particularly well. The researchers suspect that since these mitochondria come from the cold-loving S. eubayanus, they are better suited to the brewing conditions needed for lager.
After 250 generations, the researchers found that the improvements had stabilized. The final hybrid, called H3-E, was a more efficient fermenter than its ancestors. It was also more hardy and more flavorful. Compared to the citrus flavor of a commercial lager, the H3-E hybrid is spicy with a hint of clove. (Even wine drinkers might be tempted.) When the researchers presented their work at a microbiology conference in Chile last year, they did so with 500 liters of their brew. It was a hit. “People were unhappy when it was over,” says Dr. Cubillos. Breweries in Chile have since used their hybrid for local competitions and to sell to customers in limited-edition batches.
However, don’t try to order it from a nearby pub just yet. Commercial lager yeast typically ferments in seven days, half the time it takes for the new hybrid. That would slow down large-scale production. But Dr Cubillos and his team are refining their technique, and are optimistic about the future. All it takes is one drink.
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© 2024, The Economist Newspaper Limited. All rights reserved. From The Economist, published under licence. Original content can be found at www.economist.com.
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