EPR studies of the free radical kinetics in γ-rays irradiated Pleurotus ostreatus oyster mushrooms

The results concerning the free radicals kinetics of 60Co gamma-ray irradiated Pleurotus ostreatus (Jacq. ex Fr.) dehydrated mushroom as observed by EPR are presented and discussed. Throughout irradiation, the amplitude of the free radicals EPR spectra gradually increases with the absorbed dose by following a saturated exponential dependence. During a 100 °C isothermal annealing, the EPR signal showed a sharp decrease within the first 3 min followed by an almost constant growth for the next 2 h. An Arrhenius plot of the EPR amplitude of the same samples illustrates three different regimes, corresponding to three different kinetic patterns of recombination and creation of the free radicals, each regime being characterized by its own activation energy whose value was calculated and discussed.