Antioxidant Activities of Hops (Humulus lupulus) and Their Products. Yumei Liu (1,2), Xiao-hong Gu, and Jian Tang, Key Laboratory of Food Science and Safety, Ministry of Education, Southern Yangtze University, Wuxi, Jiangsu, China; and Kuifang Liu, College of Chemistry and Chemical Engineering, Xinjiang University, Urumqi, Xinjiang, China. (1) Corresponding author. E-mail: <xjdxlym@sina.com> (2) Current address: College of Chemistry and Chemical Engineering, Xinjiang University, Urumqi, 830046, Xinjiang, China. J. Am. Soc. Brew. Chem. 65(2):116-121, 2007.

This study aims to evaluate the total antioxidant activity and hydroxyl free radical scavenging activities of hops and their products. Dried hop cones of five varieties (SA-1, Chinook, Nugget, Marco Polo, and Tsingdao) were used in the study. The hop extracts were prepared with hot water, ethanol, and CO(2) as a solvent. The antioxidant activities of hop bitter acids, isomerized hop bitter acids, hop oil, and hexahydro-beta-acids also were evaluated, and di-tert-butylated hydroxytoluene and rutin were used for comparison. Antioxidant activities of samples were evaluated using two complementary in vitro assays: inhibition of hydroxyl radicals and protection of a beta-carotene–linoleic acid model system. All hop samples showed varying degrees of antioxidant capacity and hydroxyl radical scavenging at the tested level; hop alpha-acids exhibited significant hydroxyl radical scavenging, as well as antioxidant activity, in vitro. In ethanol and CO(2) extracts, Marco Polo showed the highest antioxidant capacity and hydroxyl radical scavenging activity. Keywords: Antioxidant activity, Hops