{
  "abstract": "[Conclusion] Iso-co-humulone does not necessarily contribute to the roughness of beer bitterness. The long-repeated rule that a high cohumulone proportion produces rough, harsh, or lingering bitterness should not be accepted as a general law of brewing and should not be used by itself to judge hop quality or to predict the sensory quality of beer. [Background] The cohumulone–roughness hypothesis has been reproduced for decades in brewing literature, referenceworks, trainingmaterials, andhop-selectionpractice, despite limiteddirect evidence and timeintensity findings inconsistentwith a simple universal rule. This persistence is consequential: brewers, particularly those entering the field, may reject otherwise suitable hops or misdiagnose rough bitterness solely from a cohumulone specification. [Methods] Fractions containing iso-co-humulone, iso-normal-humulone, or iso-ad-humulone (each combining its cis and trans forms) were added separately to unhopped beer at 25 BU. Lingering bitter aftertaste was evaluated blind by six trained panelists on a nine-point anchored scale and by a lipid-membrane taste-sensing system. In a separate 3,000-L brewing comparison, the iso-co-humulone proportion was increased from 28.2% to 39.8%; eight trained panelists performed blind paired comparisons of lingering aftertaste and bitterness crispness (kire). [Results]Mean lingering-bitterness scores were 4.9, 6.2, and 6.9 for iso-co-humulone, iso-normal-humulone, and iso-ad-humulone, respectively. Corresponding taste-sensor aftertaste responses were 0.24, 2.89, and 2.73. In the brewing comparison, aftertaste choices were divided 4:4, whereas seven of eight panelists selected the higheriso-co-humulone beer as having greater crispness (one-sided exact p = 0.035; two-sided p = 0.070). [Interpretation] Roughness was not measured as a separate multidimensional attribute, and the brewing comparison was not independently replicated. Nevertheless, the convergent model-beer, sensor, and brewing observations contradict the necessary-persistence premise of the traditional roughness rule and do not justify treating a high iso-co-humulone proportion as automatic evidence of rough beer bitterness. A cohumulone percentage on a hop specification is not a sensory verdict.",
  "abstract_shown": true,
  "affiliations": [
    "Brewing Research and Development Laboratory",
    "Asahi Breweries, Ltd."
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 1,
  "authors": [
    {
      "affs": [
        0,
        1
      ],
      "name": "Toru KISHIMOTO",
      "orcid": "0000-0003-4556-0709"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/dvewb5c889gah.bib",
  "cited_by": 0,
  "doi": "10.26434/chemrxiv.15008934/v1",
  "fulltext_url": null,
  "id": "dvewb5c889gah",
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  "landing_url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008934/v1",
  "language": null,
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "journal",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "3004|Hops Chemistry and Applications"
    ]
  ],
  "openalex": "W7213444174",
  "pdf_url": null,
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-16",
  "publisher": "American Chemical Society (ACS)",
  "ris": "https://research.draconitic.com/paper/dvewb5c889gah.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:19Z",
      "native_id": "10.26434/chemrxiv.15008934",
      "source": "chemrxiv",
      "url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008934/v2"
    }
  ],
  "subjects": [
    {
      "field": "medicine",
      "origin": "openalex:3004|Hops Chemistry and Applications",
      "subfield": "pharmacology-toxicology"
    }
  ],
  "title": "Iso-co-humulone Does Not Necessarily Contribute to the Roughness of Beer Bitterness",
  "title_text": "Iso-co-humulone Does Not Necessarily Contribute to the Roughness of Beer Bitterness",
  "type": "preprint",
  "updated_at": "2026-10-30T12:17:22Z",
  "url": "https://research.draconitic.com/paper/dvewb5c889gah",
  "venue": "ChemRxiv",
  "versions": []
}