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News — MOSCOW, Idaho — Nov. 7, 2024 — A potential solution to a common beer-spoiling menace could be bubbling up from an unexpected source, thanks to research led by Paul Rowley, an associate professor of microbiology at University of Idaho.

The culprit? Diastatic yeasts — pesky microorganisms that can wreak havoc in brewing by over-fermenting beer, boosting alcohol content, altering flavors and, worst of all, causing bottles to explode. But Rowley believes the answer might lie in another type of yeast — specifically “killer” yeasts, which could stop diastatic strains in their tracks.

“We have studied killer yeasts for years, but never considered using them to help brewers,” Rowley said.

Rowley and his team of undergraduate microbiologists at U of I, along with brewers at Rhinegeist Brewery in Cincinnati, recently published a study in the journal showing that these “killer” toxins — proteins produced by certain strains of yeast — could stop up to 95% of these diastatic spoilers. This discovery hints at a future in which brewers might avoid costly contamination issues with a little help from these microscopic defenders.

Experiments in large 1,000-liter fermenters found that adding yeasts that make killer toxins to a contaminated batch of beer prevented spoilage and the explosion of bottled beer.

Breweries do have procedures in place to prevent contamination, but diastatic yeasts are hard to identify as they look like any other yeast when put under a microscope. At large breweries, beer is often pasteurized, but the process is expensive. Given the rise in popularity of small craft brewers, there are numerous facilities out there lacking pasteurization systems. In a small-scale brewer’s eyes, fixing the problem without resorting to pasteurization is ideal because diastatic yeasts can change the taste of the delicately flavored beer, leading to off-putting flavors described as papery, wet, cardboard-like, leathery or even “catty.”

“It is rewarding that our fundamental studies of yeast toxins have the potential for future commercialization,” Rowley said. “This innovation is a potential game-changer for small craft breweries that regularly suffer significant losses from diastatic yeast contamination.”