Assessment of airborne microorganisms in a craft brewery

Microbiology Session
Amanda (Mandy) L Miller, Colorado State University, Fort Collins, CO USA
Co-author(s): Marisa Bunning, Martha Stone, Doreene Hyatt, and James ZumBrunnen, Colorado State University, Fort Collins, CO, USA

ABSTRACT: Pathogenic bacteria have little chance of surviving in beer due to intrinsic antimicrobial hurdles; however, there are other microorganisms capable of persisting in the environment and causing undesirable changes that spoil beer. The quality of all food products including beer is affected not only by the integrity of raw materials and cleanliness of the equipment and packaging materials, but also by the purity of the environmental air surrounding the processing area. Bottling and canning lines in breweries often are considered non-closed production equipment and have the ability to become contaminated from outside sources, including the environment. The purpose of this project was to examine the environmental microbial air quality within various areas of a craft brewery with emphasis on potential beer spoiling bacteria. Air samples were collected inside and outside the brewery to establish a baseline of data, identify areas of concern, and examine the effects of seasonality. Areas of concern then were sampled more often based on the risk of product contamination. The air was sampled 307 times over 22 months using an automated impaction sieve sampler pulling 80 L of air, and samples were plated both aerobically and anaerobically. Aerobic results were used to evaluate general cleanliness, while anaerobic testing was included to assess the prevalence of beer spoiling organisms. The canning line within the brewery was identified as a specific area of concern and was predicted to be contaminated with beer spoiling bacteria an average 75% of the time. Seasonality impacted aerobic microorganism levels, with fivefold increases observed in the spring. The results of this study revealed that testing for airborne microorganisms is highly recommended in the craft brewing industry. Critical areas in the brewery, such as the bottling and canning lines, should be routinely tested for airborne microorganisms to prevent final product contamination.

Amanda (Mandy) Miller received an M.S. degree in food science, with an emphasis on food safety, from Colorado State University in Fort Collins, CO, in 2011. In 1999, she began working at New Belgium Brewing Company in the Quality Assurance Department. After 10 years working as a quality assurance analyst, she now holds the position of beverage safety and sanitation specialist within the Risk Management and Environmental Affairs Department. She has been a member of ASBC for more than 10 years and a member of MBAA for more than 5 years.