ASBC 2001 meeting abstract - Hop acids: Their antimicrobial properties, their uses in brewing and their potential use as bacteriocides in other applications.

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Hop acids: Their antimicrobial properties, their uses in brewing and their potential use as bacteriocides in other applications.
MICHAEL BARNEY, John Seabrooks, and David Ryder, Miller Brewing Company.

Hop acids and their derivatives are well known to have antimicrobial properties in beer but are not equally effective against spoilage bacteria. Beers that are less bitter are also typically more susceptible to spoilage by lactic acid bacteria (LAB). Hydrogenated, reduced, isomerized alpha acids are shown be more effective than isomerized alpha acids at killing LAB. Some beta acid derivatives are surprisingly potent antimicrobials. Hop acids also work synergistically with inorganic or organic acids for disinfecting brewer's yeast. Acid treatment is rather ineffective at disinfecting yeast that has not been exposed to hops. Adding hop acids to yeast before acid treatment greatly increases the effectiveness of disinfection. Tetrahydroisohumulone was the most effective compound tested for use with acid disinfection and was even effective against acid resistant LAB. Tetrahydroisohumulone also increases the effectiveness of acidified ammonium persulfate disinfection. Hop acids effectively kill many bacteria other than beer spoilers. They are effective against all Gram positive bacteria tested including important human pathogens and have potential as natural preservatives in a number of applications. Examples include 1) use in oral care products to kill tooth decay causing bacteria (Streptococcus mutans). 2) Use to kill food-borne pathogens (Listeria, Staphylococcus, Bacillus, Clostridium). 3) Use to kill acne and skin infection-causing bacteria (Propionobacter, Staphylococcus). 4) Use in products to kill toxic shock syndrome causing bacteria (Staphylococcus aureus).

Michael Barney attended the University of Illinois and the University of Wisconsin-Oshkosh and received his bachelor's and master's degrees in Microbiology from UW-O. He did post graduate studies towards a Ph.D. in microbiology at the Medical College of Wisconsin. He is a member of the American Society for Microbiology, the Institute of Food Technologist, the Master Brewers Association of the Americas and that American Society of Brewing Chemists. Michael joined the Research Department of the Miller Brewing Company in 1973. His current title is Principal Research Scientist. His research has dealt with many aspects of brewing microbiology including food product safety, microbiological stabilization of beers, rapid methods for detecting and identifying beer spoilage microorganisms, yeast handling and genetic improvement of brewer's yeast. In addition to his research projects, Michael instructs Brewing Microbiology in-house at Miller as well as at the Siebel Institute. He has multiple publications and patents in the field and has presented lectures on Brewing Microbiology and Rapid Microbiological Methods at several universities, workshops and professional society meetings.