Abstract Although long renowned worldwide for its unique dry-hopped (DH) Trappist beer, Belgium did not develop this process for other brands until the last decade. Twenty-one commercial Belgian DH beers were investigated and compared with a few other typical Belgian beers whose production involves either late hopping or aged hop addition (Gueuze). Bitterness was determined by spectrophotometric measurements (isooctane extraction) and by reversed phase high performance liquid chromatographic with UV detector (RP-HPLC-UV) (simultaneous quantitation of humulones, cis-/trans-isohumulones, reduced isohumulones, humulinones, and hulupones). In dry-hopped Belgian beers, humulinones (found at concentrations up to 13.3 mg/L) were estimated to be responsible for up to 28% of their bitterness. As humulinones revealed to be gradually lost through boiling (22%), clarification (5%), and fermentation (14%), non-dry-hopped (NDH) beers often displayed levels below 1.7 mg/L. Even in Gueuze beers for which old, humulinone-containing hops are used, no humulinone was found. Contrary to humulones, which were detected up to 7.2 mg/L in DH beers, hulupones were found at less than 3 mg/L in all Belgian beer styles. Humulinones were not produced in the boiling wort from humulones (in contrast to hulupones, readily synthesized from lupulones) but were significantly solubilized from hop thanks to their hydrophilicity. Yet, while the co-form accounted for about 50% of the humulones, the n-form prevailed for humulinones. Some humulinone degradation products were evidenced by RP-HPLC-MS/MS, and as suggested by their retention time (RT), should be more polar than their precursors. Bottle refermentation emerged as an additional critical step of humulinone loss, explaining the low levels found even in some strongly DH beers.

中文翻译：

---

为什么 Humulinones 只有在干啤酒花后才是关键的苦味成分：与其他比利时风格的比较

摘要 尽管长期以来以其独特的干啤酒花 (DH) 特拉普斯特啤酒享誉全球，但比利时直到最近十年才为其他品牌开发了这种工艺。对 21 种商业比利时 DH 啤酒进行了调查，并与其他一些典型的比利时啤酒进行了比较，这些啤酒的生产涉及后期啤酒花或添加陈年啤酒花 (Gueuze)。苦味通过分光光度法测量（异辛烷提取）和反相高效液相色谱与紫外检测器 (RP-HPLC-UV)（同时定量葎草酮、顺式/反式异葎草酮、还原异葎草酮、葎草酮和葎草酮）来确定。在干啤酒花比利时啤酒中，葎草酮（浓度高达 13.3 mg/L）据估计占其苦味的 28%。由于腐殖质酮通过煮沸 (22%)、澄清 (5%) 和发酵 (14%) 逐渐流失，因此非干啤酒花 (NDH) 啤酒通常显示低于 1.7 mg/L 的水平。即使在使用含有腐殖质酮的旧啤酒花的 Gueuze 啤酒中，也没有发现腐殖质酮。与在 DH 啤酒中检测到高达 7.2 毫克/升的葎草酮相反，在所有比利时啤酒风格中发现的葎草酮低于 3 毫克/升。葎草酮在煮沸的麦芽汁中不会产生葎草酮（与葎草酮不同，葎草酮很容易从羽扇豆酮合成），但由于其亲水性，从啤酒花中显着溶解。然而，虽然共形式约占葎草酮的 50%，但 n 型占葎草酮的优势。RP-HPLC-MS/MS 证实了一些葎草酮降解产物，并且如它们的保留时间 (RT) 所示，应该比它们的前身更具极性。瓶装参考作为 humulinone 损失的另一个关键步骤出现，解释了即使在一些强 DH 啤酒中也发现的低水平。