Gamma response of Radix W in the dose range of 1kGy to 10kGy was investigated using a readout wavelength of 280nm. The dose response curve was linear, and the residuals of calibration curve were within about 5%. Besides, coefficients of variation at different doses were within 1%. The influence of irradiation temperature on the dose response was negligibly small in the range of 10-30°C. Influence of post-irradiation temperature was less than 3% at 5%°C-30°C even after 12 hour storage. Therefore, Radix W enables to measure precisely doses in the range of 1kGy-150kGy by choosing suitably two different readout wavelengths, 320nm for 5kGy-150kGy and 280nm for 1kGy-10kGy. Radix W can be applied to practical use in industrial radiation processing.

View full abstract

The purpose of the study is to investigate the condition of microbial growth recovery from the damage of killing stresses such as heating and ⁶⁰Co-gamma irradiation especially within the processed meat products. Black pepper powder treated by each process in which less than 1000 microbial loads was enumerated by aerobic plate counts was mixed with minced sausage and incubated at 30°C for several days. Outgrowth of microorganism was monitored according to the procedure described by Japanese Food Hygiene Law.
Sausage samples containing the treated black pepper powder showed the similar microbial growth from less than 1000 CFU/g of the sample to approximately the order of 10⁹ CPU/g of the sample during the incubation at 30°C, irrespective of gamma-irradiation or superheated-steam treatment. There were no significant differences between gamma-irradiation and superheated-steam treatment in outgrowth of the surviving microorganisms when the treated black pepper or sage was mixed and pulverized with sausage. In case paprika, growth delay of the super-steamed survivors was observed within 1 day after incubation.

View full abstract

Electron spin relaxation behaviors of radiation induced radicals were studied by the continuous microwave saturation method of electron spin resonance (ESR) spectra. Radiation induced radicals in kampo extractions yielded a sharp and intense ESR signal P1 at g = 2.0 and S1 , S2 beside P1 signal. By the progressive saturation procedure, we could evaluate relaxation times (T₁ and T₂) of P1 signal. The computer program to analyze the ESR line shape using all data points on a saturation curve was applied. Based on the theoretical analysis, the relaxation behaviors of radicals were revealed. Radiation induced radicals of the specimens yielded relaxation times, T1 in the · sec and T2 in nsec ranges, respectively. Upon the irradiation, T2 is shortened. And upon the re-irradiation, T2 is not changed.

View full abstract

Electron spin resonance (ESR) spectroscopy of both experimental and theoretical aspects revealed the gamma irradiated radicals in two glucose polymers, cellulose and starch. Prior to the irradiation, ESR signals are silent in both the glucose polymers. After the irradiation, however, a singlet signal at g = 2.0 was appeared in both the glucose polymers. The twin peaks were induced at the symmetric fields in the both sides of the singlet peak in cellulose sample. Conversely, the twin peaks were invisible in starch sample. We identified the twin peaks to be a part of triplet signal and determined the molecular structure of the cellulose radical. By the theoretical simulation method, we revealed, for the first time, that the triplet signal was attributed to the hyperfine interactions with two protons in the radical. The third peak within the triplet is overlapped by the organic radical at g = 2.0. We found that the cellulose radical does not remain in the rigid limit or the static state, but rather undergoes axial rotations around both C-C and C-H bonds. Thus the triplet may be used as a dosimeter for the irradiated plant foods.

View full abstract

Effect of gamma-irradiation on sprouting and rooting of garlic was investigated. Sprouting and rooting of garlic were inhibited by irradiation of bulbs at 2 months after harvest with doses more than 30 Gy. Four weeks-later irradiation requires higher doses to complete sprouting/rooting inhibition.

View full abstract

Electron spin resonance spectrometry of the γ-irradiated fresh papayas followed by freeze-drying and powderization was performed. We found a strong single peak in the flesh was observed at g = 2.004 and attributed to organic free radicals. Using the method of Lund et al., relaxation times of the peak from 0 to 14 days-stored samples after γ-irradiation were calculated. T₂ showed a dose response, while T₁ kept almost constant by the increment of doses. The γ-radiation-induced radicals showing progressive saturation behaviors can be caused through a different pathway from indirect effects by the low LET radiations.

View full abstract