Date of Award


Document Type


Degree Name

Master of Science (MS)


Food, Nutrition, and Culinary Science

Committee Chair/Advisor

Dr. Paul Dawson

Committee Member

Dr. Julie Northcutt

Committee Member

Dr. John McGregor


There are 8,884 craft breweries producing over 23 million barrels of beer in the United States as of 2020. These 23 million barrels of craft beer account for 12.3% of the United States beer consumption in 2020. The American craft beer industry is substantial and needs to protect its product from bacterial contamination.

Overall, beer is a microbially stable product. Beers pH, ethanol levels, CO2 concentrations, the presence of hop-derived antimicrobial compounds, and low levels of O2 make beer a highly unfavorable environment for most bacterial species. Furthermore, the brewing process, which involves heat treatments and chemical sanitizers further protect beer from bacterial contamination. However, beer sometimes does become contaminated by unwanted bacteria. Primarily these bacteria are members of the Genera Lactobacillus, Pediococcus, Pectinatus, and Megasphaera. These bacteria contaminate beer due to a variety of factors that allow them to evade beer’s antibacterial properties or the process hurdles of the brewing process. Protecting beer from these spoilage organisms is crucial to maintain quality and shelf stability. Microbreweries and brewpub are especially vulnerable to bacterial contamination due to the unique challenges they face. These challenges include the use of modular chlorobutyl hose systems and mobile pumps, the overall “open” nature of smaller brewhouses and cellars exposed to the outside environment (such as opening tanks to pitch yeast, dry hop, or introduction of additions), and the proximity of the production and packaging areas to the public.

Research was conducted to determine steps in the brewing process that bacterial species were most likely to contaminate the microbrewery/brewpub environment. Samples were collected from three breweries of similar size and scale in Upstate South Carolina, from eleven common locations throughout the brewing process and analyzed via HybriScan D Beer rapid molecular testing kits for the cell counts at each location. The racking arm valve had the highest levels of bacterial contamination.



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