2016 Volume 51 Issue 1 Pages 3-10
Since γ-rays and X-rays can penetrate foods and materials, fresh raw bovine livers can be sterilized without heating after packaging. In the previous study, radicals in the livers irradiated in chilled condition were detected by using electron spin resonance spectroscopy (ESR). However, γ-irradiation of the bovine livers might be carried out in frozen condition. In this study, the livers irradiated in dry-ice were investigated for detection of radicals by using various preparations of ESR specimens. The bovine livers stuffed in straws were irradiated and measured with ESR. The existence of some dose-responsible peaks was found on differential spectra after spectra of the straw itself were subtracted. On the other hand, direct measurements of the frozen bovine livers showed a main peak and two side peaks, resulting almost straight dose-responsible lines. ESR spectra of freeze-dried powders from the livers showed a dose-responsible shoulder peak, but the side peaks disappeared. To confirm whether the radicals exist or not in the livers that were stored in the freezer for 7 days, specimens of the livers were prepared by thawing in tap water. The results indicated that the dose-responsible side peaks were still observable in the livers. In conclusion, ESR can be used as the detection method of the raw bovine livers which were irradiated in frozen condition. ESR method at liquid nitrogen temperature is suitable for the screening of the irradiated bovine livers because of its quick and easy sample preparation.