Electron spin resonance spectra of γ-irradiated citrus fruit skins, skin components and stalks

The ESR spectra of the stalks and skins of a number of non-irradiated and γ-irradiated citrus fruits suggest that ESR spectroscopy could be used to establish the irradiation history. Two major spectral changes occur up on irradiation. Two additional features appear and are only observed in irradiated specimens (Features B and D, the latter separated by c. 5.9mT) and these are accompanied by an increase in the intensity of the main central signal (Feature A). Observations on the stability of Features A and D indicate that they arise from different radicals. Experiments on the meso- and exo-carps indicate that Features B and D are located mainly in the former and Feature A mainly in the latter.