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Reference · bibliography

Sources behind the data

Hoparoma's reference tables and its aroma model are grounded in published research and supplier data. This page lists what is used where. Entries link to the publisher's page; anything we could not verify against a primary page is marked as such.

Peer-reviewed literature

Thiol precursors in hops and malt, their release by yeast, and the dose-response relationships used by the aroma model.

  1. Tominaga et al. 1998 Tominaga, T., Peyrot des Gachons, C., Dubourdieu, D. A new type of flavor precursors in Vitis vinifera L. cv. Sauvignon Blanc: S-cysteine conjugates. Journal of Agricultural and Food Chemistry 46(12), 5215–5219. DOI
    Used for: origin of the bound-precursor concept (wine)
  2. Peyrot des Gachons et al. 2000 Peyrot des Gachons, C., Tominaga, T., Dubourdieu, D. Measuring the aromatic potential of Vitis vinifera L. cv. Sauvignon Blanc grapes by assaying S-cysteine conjugates, precursors of the volatile thiols. Journal of Agricultural and Food Chemistry 48(8), 3387–3391. DOI
    Used for: precursor assay background
  3. Peyrot des Gachons et al. 2002 Peyrot des Gachons, C., Tominaga, T., Dubourdieu, D. Sulfur aroma precursor present in S-glutathione conjugate form: identification of S-3-(hexan-1-ol)-glutathione in must from Vitis vinifera L. cv. Sauvignon Blanc. Journal of Agricultural and Food Chemistry 50(14), 4076–4079. DOI
    Used for: glutathionylated precursor background
  4. Kishimoto et al. 2008 Kishimoto, T., Morimoto, M., Kobayashi, M., Yako, N., Wanikawa, A. Behaviors of 3-mercaptohexan-1-ol and 3-mercaptohexyl acetate during brewing processes. Journal of the American Society of Brewing Chemists 66(3), 192–196. DOI
    Used for: 3MH and 3MHA behaviour through the brewing process
  5. Kishimoto 2009 Kishimoto, T. Concentration of 4-mercapto-4-methylpentan-2-one and 3-mercaptohexan-1-ol in hop cultivars. Acta Horticulturae 848, 307–322 (II International Humulus Symposium). DOI
    Used for: 4MMP and 3MH differences between hop varieties (hop thiol tiers)
  6. Takoi et al. 2009 Takoi, K., Degueil, M., Shinkaruk, S., Thibon, C., Maeda, K., Ito, K., Bennetau, B., Dubourdieu, D., Tominaga, T. Identification and characteristics of new volatile thiols derived from the hop (Humulus lupulus L.) cultivar Nelson Sauvin. Journal of Agricultural and Food Chemistry 57(6), 2493–2502. DOI
    Used for: 3S4MP and 4MMP in Nelson Sauvin (hop thiol tiers)
  7. Gros et al. 2011 Gros, J., Nizet, S., Collin, S. Occurrence of odorant polyfunctional thiols in the super alpha Tomahawk hop cultivar. Comparison with the thiol-rich Nelson Sauvin bitter variety. Journal of Agricultural and Food Chemistry 59(16), 8853–8865. DOI
    Used for: variety thiol profiles
  8. Gros et al. 2012 Gros, J., Peeters, F., Collin, S. Occurrence of odorant polyfunctional thiols in beers hopped with different cultivars. First evidence of an S-cysteine conjugate in hop. Journal of Agricultural and Food Chemistry 60(32), 7805–7816. DOI
    Used for: bound (cysteinylated) 3MH precursors in hops (hop thiol tiers)
  9. Gros et al. 2013 Gros, J., Tran, T. T. H., Collin, S. Enzymatic release of odourant polyfunctional thiols from cysteine conjugates in hop. Journal of the Institute of Brewing 119(4), 221–227. DOI
    Used for: enzymatic release of bound thiols
  10. Roland et al. 2016 Roland, A., Viel, C., Reillon, F., Delpech, S., Schneider, R., Dagan, L. First identification and quantification of glutathionylated and cysteinylated precursors of 3-mercaptohexan-1-ol and 4-methyl-4-mercaptopentan-2-one in hops (Humulus lupulus). Flavour and Fragrance Journal 31(6), 455–463. DOI
    Used for: bound precursor pools in hops
  11. Roland et al. 2017 Roland, A., Delpech, S., Dagan, L. A powerful analytical indicator to drive varietal thiols release in beers: the thiol potency. BrewingScience 70(11/12), 170–175. DOI
    Used for: thiol potency as a hop indicator
  12. Lafontaine & Shellhammer 2018 Lafontaine, S. R., Shellhammer, T. H. Impact of static dry-hopping rate on the sensory and analytical profiles of beer. Journal of the Institute of Brewing 124(4), 434–442. DOI
    Used for: dose-response of dry-hop aroma (aroma model)
  13. Stevens 1957 Stevens, S. S. On the psychophysical law. Psychological Review 64(3), 153–181. DOI
    Used for: power-law scaling of perceived intensity
  14. Chenot et al. 2019 Chenot, C., Robiette, R., Collin, S. First evidence of the cysteine and glutathione conjugates of 3-sulfanylpentan-1-ol in hop (Humulus lupulus L.). Journal of Agricultural and Food Chemistry 67(14), 4002–4010. DOI
    Used for: additional bound thiol precursors in hops
  15. Michel et al. 2019 Michel, M., Haslbeck, K., Ampenberger, F., Meier-Dörnberg, T., Stretz, D., Hutzler, M., Coelhan, M., Jacob, F., Liu, Y. Screening of brewing yeast β-lyase activity and release of hop volatile thiols from precursors during fermentation. BrewingScience 72(11/12), 179–186. DOI
    Used for: β-lyase activity differences between brewing strains (yeast levels)
  16. Chenot et al. 2021 Chenot, C., Thibault de Chanvalon, E., Janssens, P., Collin, S. Modulation of the sulfanylalkyl acetate/alcohol ratio and free thiol release from cysteinylated and/or glutathionylated sulfanylalkyl alcohols in beer under different fermentation conditions. Journal of Agricultural and Food Chemistry 69(21), 6005–6012. DOI
    Used for: conversion of bound precursors during fermentation (yeast levels)
  17. Chenot et al. 2022 Chenot, C., Donck, W., Janssens, P., Collin, S. Malt and hop as sources of thiol S-conjugates: thiol-releasing property of lager yeast during fermentation. Journal of Agricultural and Food Chemistry 70(10), 3272–3279. DOI
    Used for: malt as a precursor source; lager yeast thiol release
  18. Kishimoto et al. 2022 Kishimoto, T., Hisatsune, Y., Fujita, A., Yamamoto, S., Ishikawa, T. Presence of disulfide-bonded thiols in malt and hops as the precursors of thiols in beer. Journal of Agricultural and Food Chemistry 70(41), 13413–13418. DOI
    Used for: disulfide-bonded precursors in malt and hops
  19. Molitor et al. 2022 Molitor, R. W., Roop, J. I., Denby, C. M., Depew, C. J., Liu, D. S., Stadulis, S. E., Shellhammer, T. H. The sensorial and chemical changes in beer brewed with yeast genetically modified to release polyfunctional thiols from malt and hops. Fermentation 8(8), 370. DOI
    Used for: malt-derived thiols with an engineered yeast; non-barley grains carry little
  20. Svedlund et al. 2022 Svedlund, N., Evering, S., Gibson, B., Krogerus, K. Fruits of their labour: biotransformation reactions of yeasts during brewery fermentation. Applied Microbiology and Biotechnology 106, 4929–4944. DOI
    Used for: review of yeast biotransformation (β-lyase, β-glucosidase)
  21. Fleischer & Hellwig 2022 Fleischer, K., Hellwig, M. Kilning invokes oxidative changes in malt proteins. European Food Research and Technology 249(1), 199–206 (online 2022). DOI
    Used for: protein thiol groups fall with malt colour (roast and caramel malts rated negligible)
    Measures protein thiol (–SH) oxidation versus malt colour, not aroma-thiol precursors directly.
  22. Chenot et al. 2023 Chenot, C., Collin, S., Suc, L., Roland, A. Unusual profile of thiol precursors in special malts: first evidence of chemical glutathionylation. Journal of the American Society of Brewing Chemists 82(1), 15–22 (online 2023). DOI
    Used for: malt precursor levels (pale and special malts)
  23. Krogerus et al. 2023 Krogerus, K., Rettberg, N., Gibson, B. Increased volatile thiol release during beer fermentation using constructed interspecies yeast hybrids. European Food Research and Technology 249(1), 55–69. DOI
    Used for: hybrid yeast thiol release
  24. Liu et al. 2024 Liu, Y., Dancker, P., Biendl, M., Coelhan, M. Comparison of polyfunctional thiol, element, and total essential oil contents in 32 hop varieties. Food Chemistry (2024).
    Used for: cross-variety thiol comparison
    Title, authors and journal confirmed on PubMed; DOI not recorded here.

Manufacturer and industry disclosures

Technical disclosures by yeast laboratories and hop merchants. Useful and specific, but written by the seller; read with that in mind.

  1. Lallemand 2023 Lallemand Brewing (Molitor, R. W., Shellhammer, T. H.). Hop biotransformation and yeast: a focus on releasing polyfunctional thiols during fermentation. Article
    Used for: β-lyase overview, sensory thresholds (4MMP 6 ng/L, 3MH 55 ng/L, 3MHA 5 ng/L)
  2. Lallemand 2026 Lallemand Brewing. Practical tips for thiol boosting recipes. Article
    Used for: process levers (temperature, precursor feeding); Pomona versus Verdant split batch
  3. Brew Your Own 2022 Christianson, B. Intro to thiols: tropical flavors in beer. Brew Your Own, May 2022. Article
    Used for: homebrewer-level introduction
  4. White Labs, WLP077 White Labs. WLP077 Tropicale Yeast Blend product page, and the WLP830 German Lager page describing the β-lyase screen behind the blend. Product page
    Used for: WLP077 and WLP830 ratings
  5. Omega Yeast, thiol guide Omega Yeast. Thiolized yeast unlocks tropical thiol aromas from hops and malt (brewing guide, 2026). Guide
    Used for: Cosmic Punch and Star Party background; precursor to free thiol ratio; published expression levels (about 60 ppt threshold, about 600 ppt IRC7, 6,000+ ppt patB)
  6. Omega Yeast, Helio Gazer Omega Yeast. Helio Gazer (OYL-405) Thiolized ale yeast product page. Product page
    Used for: Helio Gazer rating
    The '200x above sensory threshold' statement appears on Omega's 2022 product page.
  7. Omega Yeast, Top Crop experiment Omega Yeast (Top Crop). Experiment: Amplifying Thiols with Propper Phantasm (4 February 2026). Article
    Used for: Omega's published 3SH levels: about 600 ppt for Cosmic Punch alone, 6,000+ ppt for Helio Gazer
  8. Escarpment Labs Escarpment Laboratories. Thiol Libre product page. Product page
    Used for: Thiol Libre rating
  9. Berkeley Yeast Berkeley Yeast. Tropics strains (Tropics London, Tropics Vermont, Dry Tropics London). Product page
    Used for: Berkeley Tropics rating
  10. Fermentis, SH-45 Fermentis. SafLager SH-45 product page (lager strain selected to enhance hop thiol release). Product page
    Used for: SH-45 rating
  11. Hopsteiner 2025 Hopsteiner. Hop variety dependent thiol impact for beer brewing. Brauwelt International sponsored news / Hopsteiner newsletter, February 2025. PDF
    Used for: variety thiol-impact classification by LC-MS/MS

Hop supplier data

Brewing values and lot certificates of analysis. The crop-year rows on each hop page name the specific lot.

  1. Yakima Chief Hops Yakima Chief Hops. Variety pages, crop reports, and Survivable Compounds: a brewer's handbook (2022). Handbook
    Used for: US varieties, β-pinene and survivable compound data
  2. Hop Products Australia Hop Products Australia. Variety analytical data and crop reports 2024 and 2025. 2025 crop report
    Used for: Galaxy, Vic Secret, Eclipse, Ella, Enigma, Topaz
  3. NZ Hops NZ Hops Ltd. Variety overview sheets. Site
    Used for: New Zealand varieties
  4. BarthHaas BarthHaas. Hop Atlas and variety technical sheets. Site
    Used for: German varieties, aggregate ranges
  5. Hopsteiner Hopsteiner. Variety data sheets. Site
    Used for: Amarillo, Magnum, Saaz, Calypso, Apollo, Bravo
  6. Hop Alliance Hop Alliance. Lot-level certificates of analysis for crop years 2024 and 2025. Site
    Used for: crop-year lot rows

How the sources are used

Layer one of Hoparoma is calculation: recipe to compound concentrations, using published dose-response, decay, and saturation relationships. Layer two is perception: compound concentrations to what the beer is likely to smell like. The first layer is stated with confidence; the second is an estimate with its limits disclosed, because sensory validation of the model is still ongoing.