日本語版

hop bitter acids

compound class / compound-hop-bitter-acids

ホップ苦味酸

Hop-derived alpha-acids and related bitter acids, and their conversion products.

On this page (9 sections)
  1. Overview
  2. Sources for this overview (4)
  3. Topic hubs
  4. Follow the connections
  5. Related entries (10)
  6. Composition and content (3)
  7. Sensory (1)
  8. Mechanism and receptors (1)
  9. How processing and cooking change it (1)
↑

Reading the bitterness

Hop bitter acids are a class that collectively refers to alpha-acids derived from hops and the related bitter acids and conversion products that arise from them. In a 2016 study involving chemical analysis of 34 commercial lager brands, these acids showed diverse concentration profiles that varied by brand.

In sensory evaluation of 10 brands from the same study, the hop acid profile was related to the quality of perceived bitterness, its temporal changes, and intensity. As a central component class in building the bitterness of beer as a beverage, hop-derived bitter acids have become a subject of bitterness research.

At the receptor level, structural bioinformatics research has analyzed binding modes to 3 bitter taste receptors—TAS2R1, TAS2R14, and TAS2R40—for 10 hop-derived compounds including stereoisomers of iso-alpha-acids, alpha-acids, and 8-prenylnaringenin, using docking calculations. However, the assignment to these 3 receptors itself was not newly measured in this paper but was cited as existing knowledge, and there are no reports of cell-based receptor assays. The primary-assay literature that forms the basis has also not been reached in this instance.

In the hop plant, there is research indicating that alpha-acid accumulation is most intensive during the 3-4 week period after flowering, and variation in annual content levels (6.7-11.6% dry weight) is explained by cumulative temperature and precipitation through the subsequent technical maturation period. In beer, strongly dry-hopped styles have been reported to reach up to 159 mg/L in hop-derived phenolic compounds, matching or exceeding the concentration of humulinone or iso-alpha-acids in the same beer, allowing us to trace the relationship between resin components and polyphenolic components that carry bitterness.

Sources for this overview

  1. The impact of hop bitter acid and polyphenol profiles on the perceived bitterness of beer

    Oladokun O; Tarrega A; James S; Smart K; Hort J; Cook D / 2016 / journal article / full text checked

    Checked for this overview: Confirmed the diversity of hop bitter acid concentrations in commercial beer. / Confirmed the relationship between hop acid profile and perceived bitterness.

  2. In Silico Investigation of Bitter Hop-Derived Compounds and Their Cognate Bitter Taste Receptors

    Dunkel A; Hofmann T; Di Pizio A / 2020 / journal article / abstract checked

    Checked for this overview: Confirmed binding-mode docking analysis to 3 TAS2R receptors and its limitations.

  3. Empiric mathematical model for predicting the content of alpha-acids in hop (Humulus lupulus L.) cv. Aurora

    Srečec S; Kvaternjak I; Kaučić D; Špoljarić I; Mršić G / 2013 / journal article / full text checked

    Checked for this overview: Confirmed alpha-acid accumulation 3-4 weeks after flowering and weather factors.

  4. Beyond International Bitterness Units: Chemical Profiling of Hop Phenolics in Dry-Hopped Beers Associated with Bitterness and Astringency

    Calvert D; Hopfer H; Kwasniewski M / 2026 / journal article / abstract checked

    Checked for this overview: Confirmed that phenolic concentration during dry hopping matches resin concentration.

Follow the connections

hop bitter acids →contributes to→ bitterness →can be measured separately …→ astringency

beer →contains→ hop bitter acids

hop bitter acids →is reported to activate→ human TAS2R receptor family

hop bitter acids →transforms in solution into→ iso-α-acids (isohumulones) →contributes to→ bitterness

Structured claims — open a section to read each claim's confidence, evidence and limits

Composition and content (3)

beer contains hop bitter acidssupported

Scope: Commercial lager beers chemically analyzed in the cited study

Note: Concentration and product profile vary. / 2026-08-31: calibration-downgraded from established to supported because the supporting evidence has no full-text-checked source. May be re-upgraded once full text is checked.

Hop bitter acids in commercial beers were analyzed, and concentrations varied.
Limitations: Composition specific to each product.
Source: The impact of hop bitter acid and polyphenol profiles on the perceived bitterness of beer (Oladokun O; Tarrega A; James S; Smart K; Hort J; Cook D, 2016) · abstract checked
Show dataingredient-beer —contains→ compound-hop-bitter-acids
claim: clm-beer-contains-hop-acids / type: composition / updated: 2026-08-31
polyphenols reaches concentrations comparable to hop bitter acidspreliminary

Scope: LC-MS/MS profiling of 81 structurally annotated hop-derived phenolic and resin compounds across a wide range of commercial beers

Note: Concentration parity is not by itself sensory contribution: the authors state that the sensory role of hop phenols remains poorly understood, and present the implications for bitterness and mouthfeel as a suggestion.

81 hop-derived compounds were structurally annotated; the most abundant phenols were flavonol and phloroglucinol glycosides, chlorogenic acids, prenylflavonoids, and procyanidins. Intensely dry-hopped styles contained up to 159 mg/L of hop phenols, matching or exceeding humulinones and iso-α-acids. In PCA, the resin profile distinguished beer styles mainly through the ratio of iso-α-acids to oxidized resins, while the phenol profile appeared to reflect the dry-hop dosage and hop product used. The authors conclude that hop phenols, especially flavonol glycosides, transfer during dry hopping at a much higher rate than resins.
Limitations: Abstract-level extraction; the number of beers is not stated. This is composition only, with no sensory panel reported, and concentration parity does not establish parity of bitterness contribution — all the more so because the taste thresholds of these phenol classes differ greatly.
Source: Beyond International Bitterness Units: Chemical Profiling of Hop Phenolics in Dry-Hopped Beers Associated with Bitterness and Astringency (Calvert D; Hopfer H; Kwasniewski M, 2026) · abstract checked
Show datacompound-polyphenols —reaches_concentrations_comparable_to→ compound-hop-bitter-acids
claim: clm-hop-phenolics-dry-hopped-levels / type: composition / updated: 2026-08-30
hop bitter acids increases in hops with Weeks after flowering, with accumulation most intensive in weeks 3 and 4 in particular. A model has been proposed under which alpha-acid content is governed by the sum of effective accumulated temperature and precipitation from the secondary sprouting after spring pruning through to the cone's technological maturity (optimal harvest stage).supported

Scope: Verified against measured data for cv. Aurora, using 6 growing seasons in Croatia (Gregurovec, 2001-2006) plus 1 growing season in Slovenia (Žalec, 2012)

Note: Even though sampling was done at the same technological maturity (optimal harvest stage), alpha-acid content varied from year to year, from 6.7% to 11.6% (dry weight), and the authors attribute this mainly to weather conditions (a positive effect from precipitation, a negative effect from temperature). Data quantifying the decline in content once the optimal harvest stage has passed could not be confirmed from this paper.

Verbatim: "Accumulation of alpha acids is most intensive in third and fourth week after hop flowering." Alpha-acid content (% dry weight, measured at technological maturity, cv. Aurora) was 11.6% in 2001, 11.1% in 2002, 6.7% in 2003, 10.0% in 2004, 9.7% in 2005, and 9.3% in 2006 at Gregurovec, Croatia, and 10.2% in 2012 at Žalec, Slovenia. A positive effect of precipitation and a negative effect of temperature were shown in the regression model, and the model's fit worsened in a drought year such as 2003 (July potential evapotranspiration above 4.5 mm/day).
Limitations: Result for a single cultivar (Aurora). The description that accumulation is most intensive is limited to the statement that it occurs in weeks 3-4 after flowering, and is not data quantifying the decline in content once the optimal harvest stage has passed.
Source: Empiric mathematical model for predicting the content of alpha-acids in hop (Humulus lupulus L.) cv. Aurora (Srečec S; Kvaternjak I; Kaučić D; Špoljarić I; Mršić G, 2013) · full text checked
Show datacompound-hop-bitter-acids —increases_in_hops_with→ "Weeks after flowering, with accumulation most intensive in weeks 3 and 4 in particular. A model has been proposed under which alpha-acid content is governed by the sum of effective accumulated temperature and precipitation from the secondary sprouting after spring pruning through to the cone's technological maturity (optimal harvest stage)."
claim: clm-w37h-hops-alpha-acid-flowering-weeks / type: composition / updated: 2026-09-02

Sensory (1)

hop bitter acids contributes to bitternesssupported

Scope: Commercial beers in the cited hop-profile study

Note: The type of hop acid, its oxidation state, and the beer matrix affect its temporal character.

The hop acid profile was associated with the nature, temporal profile, and intensity of perceived beer bitterness.
Limitations: Commercial products and descriptors from the study's own panel.
Source: The impact of hop bitter acid and polyphenol profiles on the perceived bitterness of beer (Oladokun O; Tarrega A; James S; Smart K; Hort J; Cook D, 2016) · abstract checked
Show datacompound-hop-bitter-acids —contribute_to→ sensation-bitter
claim: clm-hop-acids-bitter / type: sensory / updated: 2026-08-30

Mechanism and receptors (1)

hop bitter acids is reported to activate human TAS2R receptor familysupported

Scope: Hop-derived bitter compounds including iso-α-acid stereoisomers, α-acids, and 8-prenylnaringenin

Note: Recorded from a structural bioinformatics paper that restates the attribution to the 3 receptors as established prior knowledge. The underlying receptor-assay source (Intelmann et al. 2009, Chemosensory Perception) could not be obtained in abstract or full text and is listed as metadata_only in sources.csv. Per-receptor entities (receptor-tas2r1 / tas2r14 / tas2r40) have deliberately not been created until the assay-level source can be read.

The abstract states that the bitterness of hop-derived compounds was found to be mediated by 3 bitter taste receptors, TAS2R1, TAS2R14, and TAS2R40, and reports a structural bioinformatics characterization of the binding modes of trans-/cis-isocohumulone, -isohumulone, -isoadhumulone, cohumulone, humulone, adhumulone, and 8-prenylnaringenin at the orthosteric binding sites of these receptors. A conserved asparagine in transmembrane helix 3 is essential for recognizing hop-derived compounds, and the surrounding binding-site residues determine ligand specificity.
Limitations: The attribution to the 3 receptors is presented as established prior knowledge rather than a new measurement in this paper, and the abstract reports no cell-based receptor assay. The underlying primary assay literature (Intelmann et al. 2009, Chemosensory Perception, DOI 10.1007/s12078-009-9049-1) could not be read in this survey and is registered as metadata_only. The docking results are computational predictions, not measured activation.
Source: In Silico Investigation of Bitter Hop-Derived Compounds and Their Cognate Bitter Taste Receptors (Dunkel A; Hofmann T; Di Pizio A, 2020) · abstract checked
Plasmids encoding 25 human TAS2Rs were transiently expressed in HEK293T cells and stimulated with 15 hop-derived compounds including α-acids, β-acids, trans/cis-iso-α-acids, isoxanthohumol, xanthohumol, and 8-prenylnaringenin. Depending on chemical structure, these activated hTAS2R1, hTAS2R14, and hTAS2R40.
Limitations: Only the abstract was checked.
Source: Three TAS2R Bitter Taste Receptors Mediate the Psychophysical Responses to Bitter Compounds of Hops (Humulus lupulus L.) and Beer (Intelmann D; Batram C; Kuhn C; Haseleu G; Meyerhof W; Hofmann T, 2009) · abstract checked
Limits: The threshold concentrations and EC50 values obtained from the receptor assay were far lower than the values determined in human psychophysical experiments. However, the rank order of potency across compounds was similar between the two experiments.
Limitations: Abstract checked only. This limitation guards against treating the in vitro threshold as a human perceptual threshold.
Source: Three TAS2R Bitter Taste Receptors Mediate the Psychophysical Responses to Bitter Compounds of Hops (Humulus lupulus L.) and Beer (Intelmann D; Batram C; Kuhn C; Haseleu G; Meyerhof W; Hofmann T, 2009) · abstract checked
Show datacompound-hop-bitter-acids —is_reported_to_activate→ receptor-tas2r-family
claim: clm-hop-bitter-compounds-tas2r-triple / type: mechanism / updated: 2026-08-30

How processing and cooking change it (1)

hop bitter acids transforms in solution into iso-α-acids (isohumulones)supported

Scope: Rutnik 2023, 3 Slovenian hop varieties, HSI 0.3–0.7, the 90-minute boiling condition

Note: The isomerization rate (conversion proportion) differed by hop variety; it is reported that Celeia converted at a higher rate than Aurora or Styrian Wolf.

α-acid concentration in beer boiled for 90 minutes became nearly zero, and it was concluded that nearly all of the α-acids that transferred into the wort had been isomerized or converted to other compounds. The proportion isomerized depended on hop variety, with Celeia converting at a higher rate than Aurora or Styrian Wolf.
Limitations: The description used is 「ほぼゼロ」 (in translation: "nearly zero"); the limit of quantification and the specific residual concentration figure are not given in the relevant part of the text.
Source: The Impact of Hop Freshness on Kettle-Hopped Beers (Rutnik K; Ocvirk M; Košir IJ, 2023) · full text checked
Show datacompound-hop-bitter-acids —transforms_in_solution_into→ compound-iso-alpha-acids
claim: clm-iaa-alpha-acid-near-complete-conversion-90min / type: processing / updated: 2026-09-15

↑ Top of page · ← Encyclopedia (English entries)