DETERMINATION OF ISO-ALPHA-ACIDS, ALPHA-ACIDS AND BETA-ACIDS IN HOP AND ISOMERIZED HOP EXTRACTS - A COLLABORATIVE TRIAL

A method, for the determination of iso-alpha-, alpha- and beta-acids i n hop and isomerized hop extracts, has been collaboratively tested by members of the European Brewery Convention Analysis Committee and the Arbeitsgruppe Hopfenanalyse. The method, which relies on high performa nce liquid chromatography with a solvent programme, is recommended for use. It was judged that repeatability (r95) values for alpha- and bet a-acids were independent of concentration, whereas the value for iso-a lpha-acids and reproducibility (R95) values for alpha-, beta- and iso- alpha-acids were dependent on concentration. Values of r95 and R95 res pectively were for: alpha-acids, 0.91 and -0.41 + 0.057 m, over the ra nge 29.4 to 62.7% m/m; beta-acids, 0.67 and -0.20 + 0.119 m, over the range 8.5 to 20.9% m/m and iso-alpha-acids, 0.15 + 0.024 m and 0.39 0.073 m. over the range 3.3 to 81% m/m.