BITTERNESS OF CONGENERS AND STEREOISOMERS OF HOP-DERIVED BITTER ACIDSFOUND IN BEER

The sensory bitterness intensity of the major hop bitter acids has bee n shown to vary. The cis- and trans-isomers of isocohumulone and isohu mulone were isolated and purified by preparative high-performance liqu id chromatography. These compounds were tested by seven tasters over a concentration range of 16.6-166 mu M in a model phosphate-buffered sy stem and compared with quinine sulfate (13.1-131 mu M). More than 1,20 0 two-glass taste tests were carried out. Over these concentration ran ges, the sensory attributes of these substances obeyed the Stevens' ps ychophysical power law. cis-Isohumulone was the most bitter hop acid s tudied while trans-isocohumulone was the least bitter. Further testing in an unhopped beer by six tasters demonstrated similar differences i n the bitterness intensities of hop bitter acids. These differences we re partially masked by the background flavor of the beer.