Date of Graduation

8-2017

Document Type

Thesis

Degree Name

Master of Science in Food Science (MS)

Degree Level

Graduate

Department

Food Science

Advisor

Franck Carbonero

Committee Member

Kristen Gibson

Second Committee Member

Robert Bacon

Keywords

Brewing Process, Brewing Science, Craft Beer, DNA Sequencing, Food Science, Molecular Biology

Abstract

The craft beer industry is increasing in popularity in the United States. The craft brewing process typically does not use a pasteurization step, therefore the boiling process is the primary critical control step. Any microorganisms introduced after boiling, or those that are not killed during boiling, are likely to participate in fermentation and persist in the final product. Previous culture-based studies have isolated bacteria and yeast from craft beers at specific time points, but little research has been done on the process as a whole. The objectives of this research are to (1) track bacteria development throughout the brewing process and (2) compare these results to environmental samples. Two craft breweries in Arkansas were used. Five beer styles were sampled, each for two batches. Swab samples were taken of the mash tun, boil kettle, and the fermentation tank. Samples of the raw material include the grain, hops, and any additional ingredient added during the process. Beer samples were taken at each stage of the brewing process, starting at the mash tun and ending with the final product. High throughput sequencing using the Illumina MiSeq was used to identify bacterial DNA. Results show that there were few differences between the breweries. Equipment swab microbiota was similar in bacterial composition to the beer microbiota associated with that process. Most of the bacteria found in the malt is typically isolated from soil and the environment. The boiling step reduced some bacteria abundance, but some bacteria were introduced after this step. Filtering had no impact on reducing microbial abundance. This research provides the first extensive microbiota research of craft beers in Northwest Arkansas, allows craft brewers to have a better understanding of the microbiology of their product, and will initiate further research about the role that microorganisms play on the quality of the beer.

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