M. PELTZ (1), V. Algazzali (2), T. Shellhammer (1);
(1) Oregon State University, Corvallis, OR, U.S.A.; (2) John I. Haas, Yakima, WA, U.S.A.
Extracts of known oxidized hop acids, humulinone and hulupone, were prepared from α-acid and β-acid extracts using methods developed by Cook et al. (1955) and Wright (1963). High purity humulinone (93.7%) and hulupone (92.5%) extracts were achieved through reverse-phase preparative liquid chromatography and measured using high pressure liquid chromatography (HPLC-MS). Using results from prior sensory evaluation, the purified extracts along with commercially available iso-α-acids were dosed into unhopped lager beer at approximately equi-bitter concentrations (28 mg/L humulinone, 21 mg/L hulupone, 18 mg/L iso-α-acids). The dosed beers were evaluated by a panel of 10 trained tasters using descriptive analysis. The panel rated the quality of the bitterness using five descriptive terms: peak bitterness, duration, metallic, medicinal/harsh, and vegetative. The panel was capable of discriminating the beer treatments on four of the five sensory attributes, and the results suggest that the hulupone and iso-α-acid treatments were indistinguishable in bitterness quality, while the humulinone treatment was perceived to be lower in peak bitterness, less medicinal, and shorter in duration. Previous work in our lab has demonstrated that the bitterness intensity of humulinones and hulupones is greater than previously suspected. The presence of oxidized hop acids and differences in sensory bitterness quality should be taken into account when formulating beer with aged/oxidized hops.
Meghan Peltz is a second year master’s degree student studying under Thomas Shellhammer at Oregon State University, specializing in the areas of sensory and hop chemistry. Additionally, she is an active member of the ASBC Sensory Subcommittee. Prior to pursuing a graduate degree Meghan worked at Kalsec Inc. as a sensory scientist from 2009 to 2013. There she became interested in the study of hop chemistry and sensory after her specialization in Kalsec’s hop extracts product line as a sensory panel leader, analyst, and technical sales representative. Meghan holds a graduate certificate in applied statistics from Penn State University World Campus and graduated with a B.S. degree in food science from Michigan State University.