On the Sunstruck Flavour of Beer

Gunst, F.; Verzele, M.

doi:10.1002/j.2050-0416.1978.tb03891.x

Cited by 47 publications

(17 citation statements)

References 4 publications

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“…4,5 The concentration of iso-˛-acids in the final beer is normally 10-40 mg l 1 , but they are unfortunately susceptible to degradation by oxidation and photochemical processes. 6 -10 The decomposition may lead to the formation of 3-methyl-2-butene-1-thiol that imparts an unpleasant aroma (sunstruck flavor 10,11 ) to the beer. The use of reduced iso-˛-acids was proposed four decades ago 12 as a possible solution to the degradation problem by preventing the formation of 3-methyl-2-butene-1-thiol.…”

Section: Are Isomerized Forms Of The˛-acids (Humulones) Originating Fmentioning

confidence: 99%

Characterization of reduced iso‐α‐acids derived from hops (Humulus lupulus) by NMR

Nord

Sørensen

Duus

2003

Magnetic Reson in Chemistry

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Reduced forms of iso-a-acids (isohumulones), used in modern beer brewing were separated and characterized by 1 H and 13 C NMR spectroscopy. Components from mixtures of rho-iso-a-acids, tetrahydroiso-a-acids, and hexahydro-iso-a-acids were isolated using high-performance liquid chromatography (HPLC) and analyzed by use of one-and two-dimensional NMR experiments. The data presented assign the identities of the main peaks in the HPLC traces for the reduced iso-a-acids. Previous tentative assignments regarding the cis and trans configurations and the structures of the acyl residues of the reduced iso-aacids were confirmed and extensive NMR assignments were made. Furthermore, the previously unknown stereochemistry in the C-4 side-chain of the rho-and hexahydro-iso-a-acids was assigned.

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Section: Are Isomerized Forms Of The˛-acids (Humulones) Originating Fmentioning

confidence: 99%

Characterization of reduced iso‐α‐acids derived from hops (Humulus lupulus) by NMR

Nord

Sørensen

Duus

2003

Magnetic Reson in Chemistry

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“…2,3 Beer develops an off-flavour when exposed to light because of the formation of trace amounts of 3-methyl-2-butene thiol (4), and it has been shown that the iso-alpha acids must be present for this to occur (3)(4)(5). This thiol has a taste threshold in beer of about 10 -11 mol/L, and so extremely small amounts formed by photolysis of iso-alpha acids can generate an off-flavour (6)(7)(8). In the brewing industry, beer so afflicted is termed "light-struck" and more colloquially as "skunky", since the thiol has an odor similar to that associated with skunks.…”

Section: Introductionmentioning

confidence: 98%

The photochemistry of trans-isohumulone, a bitter flavouring component of beer

Weedon¹,

Morrison²

2008

Can. J. Chem.

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Methanolic solutions of trans-isohumulone (2), a major bitter flavouring component in beer, were irradiated with UV light of 313 nm wavelength and yielded four primary products containing an enolized cyclic β-triketone moiety: cis-isohumulone (3), humulone (1), dehydro-isohumulone (7), and dehydro-humulinic acid (5). The last of these products results from loss of the 4-methyl-3-pentenoyl side chain of trans-isohumulone. Nine volatile products derived from this side chain were identified and quantitated. The identifications of all photoproducts were confirmed by independent preparation of authentic samples. No evidence of either intramolecular or intermolecular 2+2 cyclo-addition was observed. This work clarifies previous contradictory reports of the products of isohumulone photolysis and provides an example of unexpected photochemistry of an alkenyl-substituted enolized cyclic β-triketone. (2), un des constituants de la bière qui lui donne son goût amer, en solution dans le méthanol a été soumise à une irradiation UV à 313 nm et a conduit à la formation de quatre produits primaires qui contiennent une portion β-tricétonique cyclique énolisée: la cis-isohumulone (3), l'humulone (1), la déhydroisohumulone (7) et l'acide déhydrohumulinique. Le dernier de ces produits résulte de la perte de la chaîne latérale 4-méthylpent-3-énoyle de la trans-isohumulone. On a aussi identifié la nature et quantifié neuf produits volatils dérivés de cette chaîne latérale. Les identifications de tous les photoproduits ont été confirmées par la préparation d'échantillons authentiques. On n'a pas pu mettre en évidence de cycloadditions 2+2 intramoléculaire ou intermoléculaire. Ces résultats permettent de clarifier des rapports antérieurs contradictoires relatifs à la photolyse de l'isohumulone et ils fournissent un exemple de photochimie inattendue d'une β-tricétone cyclique énolisée et substituée par une chaîne alcényle. Résumé : La trans-isohumulone

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“…Kuroiwa and Hashimoto [3] and Kuroiwa et al [6] described in the early 1960s the aroma active compound 3-methylbut-2-ene-1-thiol (MBT), out of odorless precursors, as being the key compound responsible for sunstruck flavor. This substance, with an aroma threshold in water of 0.2-0.4 ng/L [7] and of 4-35 ng/L [8] in beer, is considered one of the most important aroma active compounds. Komarek et al [8] identified in beer after exposure to sunlight, besides MBT, other substances such as 3-(methylthio)-propanal, phenylacetaldehyde, 2-methylpropanal, 3-methylbutanal and an unknown compound with a sulfury odor note.…”

Section: Introductionmentioning

confidence: 99%

Variation of sunstruck flavor-related substances in malted barley, triticale and spelt

Muñoz-Insa

Gastl

Becker

2015

Eur Food Res Technol

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had a negative influence on the content of cysteine, methionine and tryptophan of triticale. The germination time and temperature showed a negative influence on the tryptophan content of spelt. With the knowledge gained, the potential of different cereals for its use in the development of malted cereal-based beverages can be determined. Moreover, the influence of malting process on the content of these substances as well as differences between the raw materials was defined.

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On the Sunstruck Flavour of Beer

Abstract: It has been confirmed that sunstruck flavour is due to the formation of 3-methyl-2-butene-1 -thiol formed by photolysis of iso-a-acids in the presence of sulphur-containing amino acids.

Cited by 47 publications

References 4 publications

Characterization of reduced iso‐α‐acids derived from hops (Humulus lupulus) by NMR

Characterization of reduced iso‐α‐acids derived from hops (Humulus lupulus) by NMR

The photochemistry of trans-isohumulone, a bitter flavouring component of beer

Variation of sunstruck flavor-related substances in malted barley, triticale and spelt

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