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Isohumulone

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Isohumulone
Names
IUPAC name 3,4-Dihydroxy-5-(3-methylbut- 2-enyl)-2-(3-methyl-1-oxobutyl)-4-(4- methyl-1-oxopent-3-enyl)-1- cyclopent-2-enone
Identifiers
CAS Number
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.042.778 Edit this at Wikidata
PubChem CID
UNII
CompTox Dashboard (EPA)
InChI
  • InChI=1S/C21H30O5/c1-12(2)7-9-15-19(24)18(16(22)11-14(5)6)20(25)21(15,26)17(23)10-8-13(3)4/h7-8,14-15,25-26H,9-11H2,1-6H3Key: QARXXMMQVDCYGZ-UHFFFAOYSA-N
  • InChI=1/C21H30O5/c1-12(2)7-9-15-19(24)18(16(22)11-14(5)6)20(25)21(15,26)17(23)10-8-13(3)4/h7-8,14-15,25-26H,9-11H2,1-6H3Key: QARXXMMQVDCYGZ-UHFFFAOYAV
SMILES
  • O=C(C1(O)C(/O)=C(\C(=O)C1C/C=C(/C)C)C(=O)CC(C)C)C\C=C(/C)C
Properties
Chemical formula C21H30O5
Molar mass 362.466 g·mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). checkY verify (what is  ?) Infobox references
Chemical compound

Isohumulones are chemical compounds that contribute to the bitter taste of beer and are in the class of compounds known as iso-alpha acids. They are found in hops.

Beer

The bitterness of beer is measured according to the International Bitterness Units scale, with one IBU corresponding to one part-per-million of isohumulone. When beer is exposed to light, these compounds can decompose in a reaction catalyzed by riboflavin to generate free-radical species by the homolytic cleavage of the exocyclic carbon-carbon bond. The cleaved acyl side-chain radical then decomposes further, expelling carbon monoxide and generating 1,1-dimethylallyl radical. This radical can finally react with sulfur-containing amino acids, such as cysteine, to create 3-methylbut-2-ene-1-thiol, a thiol which causes beer to develop a "skunky" flavor.

Formation

Isohumulones are generated by the isomerization of humulone.

Isomerization of humulone to cis- and trans-isohumulone

See also

References

  1. ^ Urban, Jan; Dahlberg, Clinton; Carroll, Brian; Kaminsky, Werner (2013). "Absolute Configuration of Beer′s Bitter Compounds". Angew. Chem. Int. Ed. 52 (5): 1553–1555. doi:10.1002/anie.201208450. PMC 3563212. PMID 23239507.
  2. "UNC chemists figure out what causes 'skunky beer'". eurekalert.org.
  3. Blanco, Carlos A.; Rojas, Antonio; Caballero, Pedro A.; Ronda, Felicidad; Gomez, Manuel; Caballero, Isabel (2006). "A better control of beer properties by predicting acidity of hop iso-α-acids". Trends in Food Science & Technology. 17 (7): 373. doi:10.1016/j.tifs.2005.11.012.
  4. Esslinger, H. M. and Narziss, L. 2003. “Beer.” in Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH Verlag GmbH & Co. KGaA, 2009 doi:10.1002/14356007.a03_421
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