Detection method of irradiated green tea using ESR

With electron spin resonance (ESR) spectroscopy, we revealed various radicals in commercially available Japanese green tea before and after γ-irradiation. The representative ESR spectrum of green tea is composed of sextet centered at g=2.0, a singlet at the same g value and a singlet at g=4.0. The first signal is attributable to a signal with hyperfine interaction of the Mn2+. The second signal is due to an organic free radical. The third signal may originate from the Fe3+. Upon irradiation, a pair of signals was newly appeared at the symmetric positions on both sides of the organic free radical signal. According to the theory of radical production in irradiated solid, a linear relationship is expected between the radiation dose and the radical yield. We determined the unreported irradiation dose by the linear extrapolation.