| Abstract: | The iso‐α‐acids and their chemically‐modified variants play a disproportionately large role in the final quality of beer. Here, fundamental aspects of two of these quality issues — foam and bitterness — are discussed. A common feature of both issues is the dependence on the hydrophobic character of the hop compounds on both bitterness potency and ability to stabilise foams. Thus the isocohumulones appear significantly less bitter than the other, more hydrophobic hop compounds. Also apparent were the differences in bitterness between the cis‐ and the trans‐isomers, with the former being the more potent. Also described are the differences in the partitioning of the cis‐ and trans‐iso‐α‐acids into beer foam. The trans‐isomers are enriched in foam relative to their cis‐counterparts and may account for the observed enrichment of cis‐isomers in the final beer relative to the common ratios observed upstream. |
