VIEW ARTICLE DOI: 10.1094/ASBCJ-49-0004
Butyric Acid Off-Flavors in Beer: Origins and Control. D. B. Hawthorne, R. D. Shaw, D. F. Davine, and T. E. Kavanagh, Carlton & United Breweries Limited/Foster's Brewing Group, Melbourne, Australia, and B. J. Clarke, Foster's Brewing Group, Melbourne, Australia. J. Am. Soc. Brew. Chem. 49:0004, 1991.
Butyric acid is an important flavor compound in a number of foods including beer. However, at concentrations above its beer flavor threshold, it causes "cheesy" or "sickly" off-flavors. Abnormal concentrations in beer can arise due to infections by anaerobic spore-forming bacteria of the genus Clostridium. Investigations into the sources of butyric acid and the bacteria showed that glucose and cane sugar syrups used as adjuncts were involved. The vulnerable areas during syrup manufacture were found to be the handling of the starch slurry during glucose syrup manufacture and the sweet water system in cane sugar syrup manufacture. Wort production was also identified as a potential source of butyric acid both before and after kettle boiling. Clostridium tertium was identified in glucose syrup adjunct tanks during one of the investigations. Good plant hygiene is essential to prevent outbreaks of the bacteria in syrup and brewing plants, particularly during periods of high ambient temperatures and after plant shutdowns. Quality control based on the analysis of butyric acid in adjuncts, wort, and beer and the microbiological detection of anaerobic spore-forming bacteria can prevent butyric acid off-flavors in beer.
Keywords: Adjunct syrups, Brewhouse, Butyric acid, Off-flavor, Clostridium spp.