Reactivity of Beer Bitter Acids Toward the 1-Hydroxyethyl Radical as Probed by Spin-Trapping Electron Paramagnetic Resonance (EPR) and Electrospray Ionization-Tandem Mass Spectrometry (ESI-MS/MS)
Contribuinte(s) |
UNIVERSIDADE DE SÃO PAULO |
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Data(s) |
20/10/2012
20/10/2012
2011
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Resumo |
The iso-alpha-acids or isohumulones are the major contributors to the bitter taste of beer, and it is well-recognized that they are degraded during beer aging. In particular, the trans-isohumulones seem to be less stable than the cis-isohumulones. The major radical identified in beer is the 1-hydroxyethyl radical; however, the reactivity between this radical and the isohumulones has not been reported until now. Therefore, we studied the reactivity of isohumulones toward the 1-hydroxyethyl radical through a competitive kinetic approach. It was observed that both cis- and trans-isohumulones and dihydroisohumulones are decomposed in the presence of 1-hydroxyethyl radicals, while the reactivities are comparable. On the other hand, the tetrahydroisohumulones did not react with 1-hydroxyethyl radicals. The apparent second-order rate constants for the reactions between the 1-hydroxyethyl radical and these compounds were determined by electron paramagnetic resonance (EPR) spectroscopy and electrospray ionization-tandem mass spectrometry [ESI(+)-MS/MS]. It follows that degradation of beer bitter acids is highly influenced by the presence of 1-hydroxyethyl radicals. The reaction products were detected by liquid chromatography electrospray ionization-ion trap-tandem mass spectrometry (LC-ESI-IT-MS/MS), and the formation of oxidized derivatives of the isohumulones was confirmed. These data help to understand the mechanism of beer degradation upon aging. Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)[09/00858-0] Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)[08/08773-0] Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)[305385/2009-7] Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) |
Identificador |
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY, v.59, n.8, p.4183-4191, 2011 0021-8561 http://producao.usp.br/handle/BDPI/31778 10.1021/jf104797d |
Idioma(s) |
eng |
Publicador |
AMER CHEMICAL SOC |
Relação |
Journal of Agricultural and Food Chemistry |
Direitos |
restrictedAccess Copyright AMER CHEMICAL SOC |
Palavras-Chave | #Isohumulones #reduced isohumulones #oxidized isohumulones #beer #1-hydroxyethyl radical #kinetics #ISO-ALPHA-ACIDS #IDENTIFICATION #CHEMISTRY #CONSTANTS #KINETICS #WINE #Agriculture, Multidisciplinary #Chemistry, Applied #Food Science & Technology |
Tipo |
article original article publishedVersion |