ESR detection of wheat flour before and after irradiation.
We revealed free radicals in wheat flour before and after gamma-ray irradiation and their thermal behavior during heat-treatment using electron spin resonance (ESR) spectroscopy. The ESR spectrum of wheat flour before irradiation consists of a sextet centered at g = 2.0 and a singlet signal at the same g-value position. The first one is attributable to a signal with hyperfine (hf) interactions of Mn2+ ion (hf constant: 7.4 mT). The second is originated from carbon-centered radical. Upon gamma-ray irradiation, however, a new signal with two triplet lines at the low and high field ends was detected in wheat flour on top of the Mn2+ sextet lines. We analyzed the triplet ESR lines as powder spectra (rhombic g-tensor symmetry) with nitrogen (14N) hyperfine interactions. This indicates that a new organic radical was induced in the conjugated protein portion of wheat flour by the gamma-ray irradiation. Intensity of the organic free radical at g = 2.0 detected in irradiated wheat flour increased monotonically by the thermal treatment. The analysis of the time-dependent evolution and decay process based on the theory of transient phenomena as well as the nonlinear least-squares numerical method provided a unique time constant for the radical evolution and decay in wheat flour during the heat-treatment.
Shimoyama
Yuhei
Y
Department of Materials Science and Engineering, Muroran Institute of Technology, Muroran 050-8585, Japan. simoyama@mmm.muroran-it.ac.jp
Ukai
Mitsuko
M
Nakamura
Hideo
H
D004307:Dose-Response Relationship, Radiation; D004578:Electron Spin Resonance Spectroscopy; D005433:Flour / Q000528:radiation effects*; D005514:Food Irradiation; D005609:Free Radicals; D005720:Gamma Rays; D014908:Triticum / Q000737:chemistry / Q000528:radiation effects*
D005609:Free Radicals