Identification of irradiated oysters by EPR measurements on shells

In this paper the EPR spectra of the radicals induced in oyster shells after irradiation to (0.5–2) kGy ionizing radiation doses are analyzed.EPR spectra of irradiated shells showed the complex radical composition of biocarbonates, characterized by the presence of SO2−, SO3− and CO2− radicals with different symmetries. In particular, the radiation-induced line at g = 2.0038, due to the gx component of the orthorhombic SO3−, was well distinguishable from the rest of the spectrum. The gx component of the orthorhombic SO3− was found to be intense and stable enough to allow the identification at least for the whole shelf life of the oyster. Furthermore, it is still well visible at low microwave powers for which the other signals are weak or non-visible and has a linear dose response in the (0.5–2) kGy range. A possible procedure protocol for the identification of irradiated oysters, can be based on acquisitions of the spectrum at low microwave power values (tenths of milliWatt) and low modulation amplitude values (0.03–0.05 mT) and on the identification of the g = 2.0038 signal as a proof of the ionizing radiation treatment performed on the sample.