Rodhouse, L. D.1 and Carbonero, F.1, (1)University of Arkansas, Fayetteville, AR, USA
Poster
The craft brewing industry is increasing in popularity in the United States and includes regional breweries, microbreweries, and home brewing. A majority of craft beers contain innovative ingredients, such as fruits, herbs, and spices that provide novel organoleptic properties to the beer. The craft brewing process typically does not use a pasteurization or filtration step; therefore, the boiling process is the primary method of inhibiting bacterial growth. Any microorganisms introduced after boiling, or those that are not killed during boiling, are likely to participate in fermentation and end up 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, starting from raw materials and finishing with the final product. The objectives of this research are to (1) track microorganism development throughout the brewing process and (2) compare these results to environmental sampling of the brewhouse to infer the origin of the microorganisms and identify those that are persistent in the environment. Two craft breweries in northwest Arkansas were utilized as the sampling source. Five beer styles were sampled, each for two distinct batches. Swab samples were taken of the mash tun, the boil kettle, and the fermentation tank. Samples of the raw material include the malted grain, hops, and any other additional ingredient added during the process. During the brewing process, a sample during the mash, before boil, post-boil, after cooling, and during fermentation, were taken. The final samples were collected after fermentation, before filtering, after filtering, and final package (cans, kegs, or bottles). High-throughput sequencing using the Illumina MiSeq will be used to identify DNA found in the samples, using both bacteria and fungi universal primers. Initial results show that the average DNA concentration of environmental swabs is 8.26 ng/µL, 15.65 ng/µL at the pre-boil stage, and 13.28 ng/µL in post-boil samples. The highest average concentration of DNA was found at the fermentation stage around day 3 at 32.92 ng/µL. In a preliminary study on an “experimental” peach sour beer, a striking bacterial diversity (at least 17 different species in significant abundance) was observed. In another preliminary study, an ESB and a red ale canned for local distribution were found to harbor slightly different potential spoilers: Lactobacilli (98%) only for the red ale, Pediococcus (47%) and diverse Lactobacilli for the ESB. The expected results of the current study will allow brewers to have more knowledge about the possibility of microorganisms found in beer and could lead to further research on the role that microorganisms play in the quality of beer and the organoleptic properties of craft beer.
Lindsey Rodhouse is a graduate student at the University of Arkansas in Fayetteville, AR, earning her master’s degree in food science, and expects to graduate in July 2017. She obtained her B.S. degree at the University of Arkansas in May 2015. Lindsey grew up in Kansas City, MO. Her passion for beer began in 2012 when she and her dad started home brewing. Since then, they have been brewing about twice annually. When Lindsey found out her master’s thesis was on the topic of beer, she could not have been more thrilled. Throughout her undergraduate and graduate career, Lindsey has been involved in the Food Science Club, Alpha Delta Pi, and the National Society for Leadership and Success. During the summer of 2014, Lindsey worked at DuPont Nutrition and Health as a food protection intern. In June 2015, she studied abroad in Italy, where she learned about food commodities in Italy. After graduating with her master’s degree, Lindsey will seek a career in the food industry.
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