Title: Characterisation of free radicals in soluble coffee by electron paramagnetic resonance spectroscopy
Authors : Pascual, Ederlinda C.
Goodman, Bernard A.
Yeretzian, Chahan
Published in : Journal of agricultural and food chemistry
Volume(Issue) : 50
Issue : 21
Pages : 6114
Pages to: 6122
Publisher / Ed. Institution : American Chemical Society
Issue Date: 2002
License (according to publishing contract) : Licence according to publishing contract
Type of review: Peer review (Publication)
Language : English
Subjects : Coffee
Subject (DDC) : 663: Beverage technology
Abstract: EPR spectra of soluble coffee display single-line free radical signals in both the solid state and aqueous solution, along with signals from the paramagnetic ions Fe(III) and Mn(II). The intensity of the free radical signal in the pure solid was estimated to be ca. 7.5 x 10(16) unpaired electrons/g, and there was no significant change on dissolution in water. In aqueous solutions, however, the free radical signal declined rapidly over ca. 10-15 min in the temperature range 20-65 degrees C, after which only slow changes were observed. This decline, which was essentially independent of atmosphere, was greatest for the lowest temperatures used, and the intensity after 1 h fitted well to an exponential curve with respect to temperature. The free radicals responsible for the single-peak EPR signal did not react with any of the spin traps tested in the present experiments, but unstable free radicals with parameters consistent with adducts of C-centered radicals were detected in coffee solutions in the presence of PBN and 4-POBN spin traps. The presence of oxygen in the solutions increased the initial rate of formation of these free radical adducts. No adducts were detected when DEPMPO was used as spin trap. However, *OH adducts of DEPMPO were shown to be unstable in the presence of coffee, a fact which illustrates the strong free radical scavenging ability of coffee solutions.
Departement: Life Sciences und Facility Management
Organisational Unit: Institute of Chemistry and Biotechnology (ICBT)
Publication type: Article in scientific Journal
DOI : 10.1021/jf020352k
ISSN: 1520-5118
URI: https://digitalcollection.zhaw.ch/handle/11475/5476
Appears in Collections:Publikationen Life Sciences und Facility Management

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