Humboldt Journal of Microbiology


Bacteria-spoilage strains are the root cause of unwanted flavors and unaesthetic appearances of beer. This accidental introduction of bacteria is causing economic loss to businesses and is affecting the health and loyalty of the breweries' consumers. The two most studied strains are from the genera Pediococcus and Lactobacillus are a result of either primary or secondary contamination from the production process. Craft beers, such as Hazy Beers, produced by small-scale breweries are more prone to spoilage than commercial beers produced by large-scale breweries. The goal of this study is to test for the presence of bacteria-spoilage strains in small-scale breweries and large-scale breweries to determine if production size has a direct effect on bacterial growth in their final product. Using the spread plate technique, we inoculated two different media with six beer samples in an anaerobic environment and observed growth using the gram staining method to identify the strain by looking at the bacteria’s morphology under the microscope. Hazy Lady IPA, produced by Six Rivers Brewery, a small-scale brewery, was the only beer in our sample size that showed significant growth on both WLDs media showing significant Lactobacillus and Pediococcus bacterial contamination. Future studies should continue to explore the relationship between production size and bacterial contamination in larger sample sizes to determine if this correlation is unique to Humboldt County’s small-scale brewery, Six Rivers, or all small-scale breweries.

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