hop β-acid transformation products

Refers to a group of transformation products that result from heating of hop β-acids (lupulones), which are bitter components of hops, during wort boiling. When hop β-acid coluprone undergoes heat treatment under conditions equivalent to wort boiling, cohulupone, hulupinic acid, nortricyclocolupone, and multiple epimeric pairs of tricyclocolupone are obtained as major products.

Recognition thresholds of these compounds ranged from 7.9 to 90.3 µmol/L depending on structure. The lowest was cohulupone at 7.9 µmol/L, described as having a short-lasting, iso-alpha acid-like bitterness. The second lowest, hydroxytricyclocolupone at 14.7 µmol/L, is described as imparting a rough bitterness that lingers from the back of the tongue through the throat. However, this is confirmation within the scope of the abstract only; panel size and threshold measurement method have not been reported.

In a study analyzing commercially available craft and lager beers by tandem mass spectrometry, 12 compounds including cohulupone and hulupinic acid were detected as 「ホップ苦味酸誘導体」 (in translation: "hop bitter acid derivatives") in beers made with abundant hops in comparison with wheat beers lacking hop aroma, based on structural level 2 identification by comparison with known fragmentation patterns. This identification indicates the presence of compounds, but confirmation by authentic reference standards or individual concentration measurements has not been performed.

In ChemTastesDB, a database compiling chemical structures of taste molecules, 13 lupone-related compounds including tricyclocolupone are classified into one cluster of 「苦味物質(Bitterant)」 (in translation: "bitter compounds (bitterants)") based on clustering by chemical structure similarity. This classification integrates structural information from existing literature; the classification itself has not newly conducted sensory evaluation and bitterness concentration or strength has not been measured.