A Review of Cyclic and Oxidative Bitter Derivatives of Alpha, Iso-Alpha and Beta-Hop Acids

Abstract

In the last decade, with the combined application of high efficiency preparation techniques, high resolution HPLC MS/MS and sophisticated NMR technologies, novel bitter derivatives of α-, iso-α-, β-acids have been identified in beer and model solutions, which has updated our knowledge of hop chemistry. In this review, newly identified cyclic and oxidative products of α-, iso-α-, β-acids in hops and beer, have been comprehensively described to give brewers a more in depth understanding of hop and beer bitterness chemistry. A total of 39 unique substances: 15 derived from α-acids, 15 from iso-α-acids, and 9 derived from β-acids are elucidated, including their structures, suggested formation mechanism, distribution profiles in model solutions or beer, reactions during fermentation, thresholds of some of these compounds, and their evolution during storage.

Keywords:

• α-acids
• β-acids
• cyclic derivative
• iso-α-acids
• oxidative derivative

Additional information

Funding

This work was supported by the Science foundation of Beibu Gulf University under grant no.17kjjh04 and no.18KYQD05, National Natural Science Foundation of China under grant no. 31801517, and Shandong Provincial Natural Science Foundation under grant no. ZR2019BC010.