Degradation of the coffee flavor compound furfuryl mercaptan in model Fenton-type reaction systems.
The stability of the coffee flavor compound furfuryl mercaptan has been investigated in aqueous solutions under Fenton-type reaction conditions. The impact of hydrogen peroxide, iron, ascorbic acid, and ethylenediaminetetraacetic acid was studied in various combinations of reagents and temperature. Furfuryl mercaptan reacts readily under Fenton-type reaction conditions, leading to up to 90% degradation within 1 h at 37 degrees C. The losses were lower when one or more of the reagents was omitted or the temperature decreased to 22 degrees C. Volatile reaction products identified were mainly dimers of furfuryl mercaptan, difurfuryl disulfide being the major compound. In addition, a large number of nonvolatile compounds was observed with molecular masses in the range of 92-510 Da. The formation of hydroxyl and carbon-centered radicals was indicated by electron paramagnetic resonance spectra using alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone or 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide as spin traps. Whereas *OH was generated by Fenton-type reactions, the C-centered radical is probably a secondary product of the reaction of *OH with various organic molecules, the reaction with furfuryl mercaptan appearing to be the most important. No evidence for S-centered radicals was seen in the spin-trapping experiments, but a sulfur-containing radical was detected when measurements were made at 77 K in the absence of spin traps.
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Imre
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Nestec Ltd., Nestlé Research Center, Vers-chez-les-Blanc, P.O. Box 44, CH-1000 Lausanne 26, Switzerland. bgoodm@scri.sari.ac.uk
Pascual
Ederlinda C
EC
Devaud
Stéphanie
S
Fay
Laurent B
LB
Stadler
Richard H
RH
Yeretzian
Chahan
C
Goodman
Bernard A
BA
D001205:Ascorbic Acid / Q000494:pharmacology; D003069:Coffee / Q000737:chemistry*; D019281:Dimerization; D004355:Drug Stability; D004492:Edetic Acid / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D005663:Furans / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry* / Q000494:pharmacology; D017665:Hydroxyl Radical / Q000737:chemistry; D007202:Indicators and Reagents; D007501:Iron / Q000737:chemistry* / Q000494:pharmacology; D013113:Spin Labels; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013649:Taste; D013696:Temperature; D014835:Volatilization
D003069:Coffee; C045076:Fenton's reagent; D005609:Free Radicals; D005663:Furans; D007202:Indicators and Reagents; D013113:Spin Labels; D013438:Sulfhydryl Compounds; C455106:furfuryl mercaptan; D017665:Hydroxyl Radical; D004492:Edetic Acid; D006861:Hydrogen Peroxide; D007501:Iron; D001205:Ascorbic Acid