MOSCOW – A promising solution to a persistent problem in brewing may emerge from an unexpected source, according to research spearheaded by Paul Rowley, an associate professor of microbiology at the University of Idaho.
The issue at hand is diastatic yeasts—microorganisms that can disrupt the brewing process by over-fermenting beer, resulting in increased alcohol content, altered flavors, and potentially catastrophic bottle explosions. However, Rowley suggests that the answer could lie in “killer” yeasts, which have the potential to inhibit these troublesome strains.
“We have studied killer yeasts for years, but never considered using them to assist brewers,” Rowley explained.
Rowley and a team of undergraduate microbiologists at U of I, in collaboration with Rhinegeist Brewery in Cincinnati, recently published findings in the journal Applied and Environmental Microbiology. Their research indicates that these killer yeasts, which produce specific proteins known as toxins, can neutralize up to 95% of diastatic yeast spoilage. This discovery opens the door for brewers to mitigate costly contamination issues with the help of these beneficial microorganisms.
In experiments conducted in large 1,000-liter fermenters, the introduction of killer toxin-producing yeasts to contaminated batches successfully prevented spoilage and the associated risks of bottle explosions.
While breweries typically implement measures to avoid contamination, diastatic yeasts are notoriously difficult to detect, often resembling harmless yeast strains under a microscope. Larger breweries often resort to pasteurization to combat this problem, a process that can be costly. With the surge in popularity of small craft breweries—many of which lack pasteurization capabilities—finding a solution that does not compromise the delicate flavors of their beers is crucial. Diastatic yeast contamination can result in off-flavors, described by brewers 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 could be a game-changer for small craft breweries that face significant losses due to diastatic yeast contamination.”
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