Beer + Science

Funk in the Glass: The Ups and Downs of Wild Microbes in Beer

From Kaitlyn Keller - PLOS Blogs

The American coolship ale is a type of beer that also utilizes the power of wild yeast and spontaneous fermentation, and is modeled after the above-mentioned Lambic style. In a 2010 PLOS ONE study, researchers investigated the microbial profiles of multiple batches of American coolship ale from a single brewer in the Northeastern United States, to see if they could establish a “microbial baseline” for this type of beer. The authors collected samples from 8 different batches throughout the 3.5- year fermentation process, and found that while the yeast and bacterial content of the beer started off with a diverse number of species, it ultimately shifted to being composed primarily of B. bruxellensis. B. bruxellensis, more commonly known as Brettanomyces bruxellensis, is the type of yeast responsible for giving beer a distinctly ‘funky,’ lightly tart flavor—it’s so distinct, in fact, that its characteristics are commonly described as ‘Bretty.’

The authors describe this particular microbial succession as likely being caused by the constantly changing environment of the beer. The strains of bacteria and yeast that initially colonized the beer produced carboxylic acid, which can limit the growth of other microbes. Once these early microbial inhabitants died off, Saccharomyces, a type of yeast commonly used in food production, and Lactobacillales were then afforded limited competition and could jump in for the main fermentation process. In the image above, the authors show how the yeast and bacterial profiles changed over time for each of the batches. They explain that since the microbial profiles and their progression are similar across all of the batches, this could be evidence that there are resident brewhouse microbiota that take over during fermentation.

It’s worth noting that studies conducted prior to this one have shown that the microbial profiles of Lambics also ultimately end up being primarily composed of B. bruxellensis, though the smaller communities of microbes differ from those found in American coolship ales.

Read the full article here.