An electron spin resonance study of dry vegetables before and after irradiation.

The ESR signals were successfully observed for the first time in dry vegetables (DVs) that are prominently used in oriental cuisines. We analyzed ESR signals of DV before and after irradiation. Before irradiation, the ESR signal of DV consisted of the three components: a singlet at g=2.0030, the sextet signals from Mn(2+) ion, and a singlet from Fe(3+). The first originated from a carbon centered organic free radical. The second is attributable to the sextet signal with hyperfine interactions of Mn(2+) ion centered at g=2.0020. The third is a singlet at g=4.0030 due to Fe(3+). After the gamma-ray irradiation, a new pair of signals, or twin peaks, appeared in the ESR spectrum of DV. The intensity of the organic free radical at g=2.0030 of the irradiated DV increased lineally with radiation doses. Progressive saturation behavior of the DV indicates a unique saturation and the signals obeyed various relaxation processes.