Using electron spin resonance (ESR) spectroscopy, we revealed three radical species in cellulose containing foods, pepper and green tea. These are commercially available in Japan. The representative ESR spectrum is composed of a sextet centered at g=2.0, a singlet at the same g-value, and a singlet at g = 4.0. The first one is attributable to a signal with hyperfine (hf) interactions of Mn²⁺ ion (hf constant: 7.4 mT). The second one is due to an organic free radical, the third one may be originated from Fe³⁺ ion.The progressive saturation behavior (PSB) of the ESR at various microwave power levels were indicated different relaxation behaviors of in those radicals. Namely, the peak intensity of the organic free radical component decreases in a monotonic fashion, whereas the Mn²⁺ and Fe³⁺ ESR signals substantially keep constant. This reflects the evidence of three independent radical species. The ESR spectrum of the cellulose containing foods shows the sames pectral feature irrespective of the tea or pepper.Upon gamma irradiation, a new pair ofsignals appeared.The PSB of the pair peaks after the irradiation showed a quite different as compared with the free radical centered at g=2.

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Effects of gamma-irradiated media containing 1% glucose on the growth of microorganisms were investigated using with strains of Saccharomyces cerevisiae 52a, Escherichia coli A4-1, S2 and Bacillus subtilis IAM1069 after irradiated at 16kGy under air-equilibrium or oxygen-equilibrium. Same growth were observed when cultivated with S.cerevisiae in the glucose media after irradiated at 16kGy under air-equilibrium or 16kGy under oxygen-equilibrium compared with heat sterilization. In the case of E coli A4-1 and S2, a little inhibition of growth were observed in irradiated media especially at oxygen-equilibrium irradiation.Strong growth inhibitions were observed in irradiated media when cultivated with B. subtilis especially remarkable at oxygenequilibrium irradiation. Irradiation of 1% glucose media caused pH drops from 7.4 to 6.6 at air-equilibrium irradiation and 6.4 at oxygen-equilibrium irradiation whereas 6.8 at heat sterilization. When these media were neutralized to pH 7.0 - 7.2, no inhibitions of growth were observed on B.subtilis between irradiated and heat sterilized media. These results indicated that cytotoxicity effects were not observed in irradiated media on these microorganisms. Similar pH drops were observed in sugar media at glucose, xylose and lactose after 16kGy irradiation whereas observed strong drop of pH at xylose by heat sterilization. From these results, pH drop of sugar media after irradiation must be considered for the design and interpretation on media effects at the wholesomeness evaluation of irradiated foods.

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The polyethylene (PE), polypropylene (PP) and polystyrene (PS) films and sheets were made with antioxidants, and the contents of additives, volatiles and other chemicals, tensile strength, color and odor were tested after gamma irradiation of 0, 10, 30 and 50 kGy dose. The antioxidants decreased uponradiation, BHT and Irgafos 168 disappeared more rapidly than Irganox 1076 and 1010. The degradation products of polymer, such as acetic acid, propionic acid, 2-methyl-2-propanol and 2, 2-dimethylpropanoic acid, were produced more in PP than PE, and the presence of antioxidants reduced their formation.On the other hand, 2, 4-di-tert-butylphenol and 2, 6-di-tert-butyl-1, 4-benzoquinone were found as degradation products of antioxidants. PP films became fragile upon irradiation and even a high level of BHT could not protect, while the combination of three antioxidants was more effective. Coloration was more pronounced, and odors were stronger in the films containing BHT. In PS sheets, the antioxidants decreased only slowly and the degradation product was formed only in small amounts.

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