Journal of the American Society of Brewing Chemists vol:67 issue:1 pages:23-32
In this study, the influence of the mashing-off temperature (78 versus 95 degrees C) on alpha-acids behavior and isomerization during wort boiling at the 10-L scale was investigated. In addition, various kettle-hopping regimes were applied to determine their possible impact on the isomerization of alpha-acids into iso-alpha-acids. As determined by quantitative HPLC as it function of wort-boiling tune, mashing-off at 95 degrees C always resulted in significantly higher hop alpha-acids utilization at the end of wore boiling (approx. 58%) compared with conventional mashing-off at 78 degrees C (approx. 42%). Moreover, with mashing-off at 95 degrees C, iso-alpha-acid profiles obtained at the end of wort boiling were potentially favorable in view of a finer, less lingering beer bitterness (relatively less isocohumulone) and prolonged bitterness stability upon aging (proportionally less trans-isomers). In regard to alternative hopping regimes, dosed addition of hop material as a function of wort boiling time resulted in similar alpha-acids utilizations compared with full hopping at the onset of the boil. Our results point to the potential of alternative ways of kettle hopping, in particular when mashing-off a. 95 degrees C, for more economic hopping combined with enhanced bitterness quality and stability.