Bitterness-modifying properties of hop polyphenols extracted from spent hop material

A polyphenolic extract was produced from spent Galena hop material and added to a low-bitterness, commercial lager beer at three levels (+0, +100, and +200 mg/L) along with iso-alpha-acids from a preisomerized Galena hop extract at two levels (+0 and +10 mg/L) to examine the impact on bitterness character by time-intensity (TI) and free-choice profiling (FCP) methods, using 11 trained panelists. Principal components analysis of the TI results separated the samples with higher levels of polyphenols and iso-alpha-acids front those with lower levels of both based on bitterness duration, maximum intensity, and area under the curve. Samples 10-100 (iso-alpha-acid/hop polyphenols) and 10-200 were significantly more bitter and had longer duration than the others. A significant effect was found for both iso-alpha-acids and polyphenols, as well as an interaction for maximum bitterness intensity and area under the curve (P < 0.001). Similarly, the results from the FCP easily separated the treatments by bitterness, lingering bitterness. and astringency. Panelists divided each of the treatments into six distinct groups based on bitterness intensity, five groups based on duration, and two to three groups based on the remaining consensus descriptors (mouthfeel, astrinency, and bitterness come-up time). Samples high in polyphenols frequently were given higher intensities for "harsh," "medicinal," and "metallic" descriptors.