Summary: Researchers have discovered that “killer toxins” produced by certain yeast strains can inhibit up to 95% of diastatic yeasts, offering a potential solution to a common craft beer spoilage problem.
Estimated reading time: 7 minutes
Craft beer enthusiasts may soon have reason to raise a glass in celebration. A team of microbiologists and brewers has uncovered a promising solution to a persistent problem plaguing small-scale breweries: diastatic yeast contamination. Their findings, published in the journal Applied and Environmental Microbiology, suggest that naturally occurring yeast proteins called “killer toxins” could be the key to preserving the quality and safety of craft beers.
Diastatic yeasts, variant strains of the common brewer’s yeast Saccharomyces cerevisiae, have long been the bane of craft brewers. These sneaky microorganisms produce an enzyme called glucoamylase, which continues to break down residual sugars in bottled beer. This unwanted fermentation can lead to off-flavors, increased alcohol content, and in extreme cases, exploding bottles.
The Killer Solution
Dr. Paul Rowley, a microbiologist at the University of Idaho and senior author of the study, explains the potential of their discovery: “If you’ve got a diastatic contamination, most of the time you just throw away the beer, and that’s expensive. What we show in the paper is that we can add the killer yeast at the point of contamination. It’s a remediation procedure to prevent the diastatic strains from taking off.”
The research team tested 34 diastatic yeast strains against eight known killer toxins produced by other Saccharomyces strains. Their results were striking: the most effective toxin, known as K1, inhibited the growth of over 91% of the diastatic strains tested. Even more impressively, some variant K2 toxins showed the ability to inhibit up to 95% of the problematic yeasts.
Why It Matters
This discovery could be a game-changer for the craft brewing industry. Unlike large commercial breweries that can afford pasteurization equipment, many small-scale operations lack the means to effectively combat diastatic yeast contamination. The current best practices mainly revolve around strict hygiene protocols and constant monitoring.
Nicholas Ketchum, a microbiologist at Rhinegeist brewery in Cincinnati and co-author of the study, highlights the potential impact: “There are more unknowns than there are knowns about the process, but this could offer an inexpensive way to remedy diastatic contamination.”
The Science Behind the Suds
To understand the significance of this research, it’s important to grasp the role of yeast in brewing. Saccharomyces cerevisiae, commonly known as brewer’s yeast, is the workhorse of fermentation. It consumes sugars from malted grains and produces alcohol and carbon dioxide as byproducts.
Diastatic yeasts are a variant of S. cerevisiae that possess an extra genetic trick up their sleeve. Dr. Rowley explains: “If you were to look at these strains on an agar plate, you couldn’t morphologically tell the difference. The only difference is that diastatic yeasts have a genetic change that gives them an extra ability to degrade residual starches.”
This extra ability becomes problematic when diastatic yeasts contaminate beers not intended for extended fermentation. The continued breakdown of complex sugars leads to hyperattenuation – a process that increases alcohol content, alters flavor profiles, and can cause dangerous over-carbonation.
From Lab to Brewery: Challenges and Opportunities
While the results are promising, the researchers caution that more work is needed before this solution can be widely implemented in breweries. The effectiveness of killer toxins appears to depend on the total yeast population, not just the presence of diastatic strains.
Dr. Rowley and his team are now investigating the prevalence of diastatic yeast contamination among small brewers and working to understand the mechanisms behind the killer toxins’ effectiveness. “Yeasts are a lot more complicated than we might think,” Rowley notes, hinting at the complexity of the microbial world that shapes our favorite brews.
The road from laboratory to brewery may be long, but for craft beer producers and enthusiasts alike, this research offers a hopeful glimpse into a future where innovative biological solutions could help preserve the quality and integrity of small-batch brews.
As the craft beer industry continues to grow and evolve, the battle against spoilage yeasts remains a critical challenge. This research not only offers a potential solution to a persistent problem but also underscores the importance of continued scientific inquiry in an industry that blends artisanal traditions with cutting-edge biotechnology.
Quiz:
- What percentage of diastatic yeast strains were inhibited by the most effective killer toxin in the study?
- What enzyme do diastatic yeasts produce that causes problems in beer?
- Why is this research particularly important for craft breweries compared to large commercial operations?
Answer Key:
- Over 91% (with some variant toxins inhibiting up to 95%)
- Glucoamylase
- Craft breweries often lack pasteurization equipment, making them more vulnerable to diastatic yeast contamination
