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)
| Autor: | Daniel R. Cardoso, Natália E. C. de Almeida, Paula Homem-de-Mello, Denis De Keukeleire |
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| Rok vydání: | 2011 |
| Předmět: |
Electrospray
Spectrometry Mass Electrospray Ionization Electrospray ionization Radical Mass spectrometry Photochemistry Tandem mass spectrometry law.invention stomatognathic system law Tandem Mass Spectrometry Electrochemistry Organic chemistry Reactivity (chemistry) Electron paramagnetic resonance Chromatography High Pressure Liquid Spin trapping Ethanol Chemistry technology industry and agriculture Electron Spin Resonance Spectroscopy food and beverages Beer General Chemistry Spin Labels General Agricultural and Biological Sciences Acids |
| Zdroj: | Journal of agricultural and food chemistry. 59(8) |
| ISSN: | 1520-5118 |
| Popis: | The iso-α-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. |
| Databáze: | OpenAIRE |
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