46. The IBU, pH, dry-hopping, ABV, and perceived bitterness—A half century of evolution in the brewing industry has affected the relevance of the IBU

Kurt Driesner (1); (1) Urban Chestnut Brewing Company, Saint Louis, MO, U.S.A.

Technical Session 13: Sensory II
Tuesday, August 16  •  8:15–9:30 a.m.
Plaza Building, Concourse Level, Governor’s Square 15

The protocol for the IBU was agreed to in 1967. In that era, almost all beers were lager- or pilsner-style, pellets and extracts were rarely used and the baled hops used were stored with little temperature control for 6-18 months before use and were excessively oxidized by today’s standards. The IBU also assumes the pH of beer is close to 4.3 and that it was not dry-hopped. Beers of the day also seldom exceeded 6.0% ABV or 50 IBUs. The world of brewing has changed drastically in the last half-century, with beers pushing close to the solubility limit for hop resins, dry-hopping that not only adds high amounts of hop compounds normally not found in beer, but increases the pH, which is known to increase perceived bitterness in beer. Un-isomerized alpha-acids and hop polyphenols solubilized in dry-hopped beers also likely alter perceived bitterness. Sour beers may have a pH as low as 3.5. This was unheard of 50 years ago and influences perceived bitterness. The relatively high and low ABV of many of the popular beer-styles today are likely to also modify perceived bitterness. These factors are explored by a trained taste panel and their influence on perceived bitterness are modeled to help brewers better understand the IBU and its relevance to their products.

Kurt Driesner completed his master’s work in environmental toxicology at Southern Illinois University in Edwardsville, IL. His previous education and experience focused on neuroscience, pharmacology, psychopharmacology, and psychology, at the University of Illinois at Urbana-Champaign. After managing a hospital program for 11 years he began working in the lab at the St. Louis Brewery during graduate school as an alternative to pharmaceutical work. He has been working at Urban Chestnut Brewing Company since 2012, where he functions as the quality assurance manager. In his time working under Brewmaster Florian Kuplent, he has gained experience as a lab manager and brewer and in brewery installation. He is a member of the MBAA, BA, and ASBC.