提升啤酒风味稳定性是当前啤酒界公认的技术难点与研究热点。贮存过程中啤酒苦味强度的下降、苦感由舒服的苦感向粗糙和后苦的苦感转化，是啤酒风味老化的一个重要表现。随着分离纯化以及鉴定检测水平的提升，国外同行对可能引起啤酒苦味粗糙与后苦的物质和反应机理进行了系统的研究，取得了突破性的进展。本文对啤酒酿造中源自酒花a酸的苦味物质，尤其是引起啤酒后苦与粗糙的三环和四环异α-酸降解产物的特性及产生机理进行了系统的介绍，旨在提升国内同行对啤酒苦味质量的认知。

It is common limiting technological problem and research focus of whole world brewing industry to improve the flavor stability with an aim to keep refreshing character of beer as long as possible to attract consumers in the shelf life of beer. A decrease of the bitterness intensity accompanied by a shift of the taste profile toward harsh and long lingering bitter after is well known phenomena observed during aging of beer. With the help of modern purification technologies, nuclear magnetic resonance spectroscopy and high resolution HPLC MS, the overseas researchers have took some breakthroughs in identifying the compounds responsible for harsh and lingering bitterness and other newly found bitter substances during brewing and storage process of beer as well as their possible transformation routs. In this paper, the highlights of the newly identified bitter compounds originated from hop a- acid were reviewed in detail, especially the formation mechanism, thresholds and elution of newly found tri- and tetra-cyclic molecules, namely main iso-α acids degraded compounds, during brewing and storage were introduced, in order to enlarge the knowledge of beer bitterness of beer brewing peers in China.