J. P. MAYE (1), R. J. Smith (2), R. J. Wilson (3);
(1) Hopsteiner, New York, NY, U.S.A.; (2) Hopsteiner, Yakima, WA, U.S.A.; (3) Hopsteiner, London, U.K.
Humulinones are formed by the oxidation of α-acids. Their detection in hops, hop pellets, and dry-hopped beers is relatively new. Humulinone formation in leaf hops and continued formation days following hop pelleting can occur in the absence of air. High HSI (hop storage index) hops have higher concentrations of humulinones than low HSI hops and concentrations as high as 0.2%–0.5% w/w are typically found in hops and hop pellets. Humulinones have been measured in dry-hopped beers at concentrations as high as 24 ppm and their bitterness has been reported to be 70% that of iso-α-acids. Air oxidation is too slow to account for the formation of humulinone in hop pellets. A mechanism of how α-acids are converted into humulinones is proposed along with detailed analysis of the concentration of humulinones found in hops, hop pellets, and dry-hopped beers will be presented.
John Paul Maye is the technical director at Hopsteiner. John Paul received his Ph.D. degree in organic chemistry from Purdue University in 1994. He started his work as a hop chemist in 1993 at Pfizer’s Brewing Ingredients Division located in Milwaukee, WI. He has published several papers and patents on hops and their applications inside and outside of brewing. In 2000 he was the recipient of the Eric Kneen Memorial Award for his publication in the Journal of the American Society of Brewing Chemists on the preparation of HPLC standards for isomerized and reduced α-acids. He is also a founding member and secretary of the International Hop Standards Committee.