Tadashi Katayama

Identification of irradiated pepper with the level of hydrogen gas as a probe

A novel method to detect whether or not a particular pepper has been irradiated has been developed which is based on the fact that H2 is formed in organic substances irradiated with ionizing radiation. Following gamma irradiation, black and white peppers were ground to powder in a gastight ceramic mill. By gas-chromatographic analysis of the gas in the mill, we observed that H2 had been released from the irradiated pepper grains. Curves plotting the H2 content vs storage time at storage temperatures of 7, 22, and 30 degrees C showed that the higher the temperatures, the smaller the H2 content, and that identification of irradiated pepper was possible for 2-4 months after 10 kGy irradiation.

Evaluation of Induced Radioactivity in 10MeV-Electron Irradiated Spices (II). .BETA.-Ray Counting.

香辛料の元素組成からリストアップされた10MeV電子線照射により生じる恐れのある (γ, n) 反応由来のβ線放出核種を検出するため照射試料のβ線計測を行った。100kGy照射した2πガスフローカウンタ, 液体シンチレーションカウンタによる計測では誘導放射能は検出されなかった。 (γ, n) 反応の標的核種を含む化合物を照射した場合の誘導放射能の値から, 天然の試料の誘導放射能は無視できるレベルであると考えられた。

Preliminary Examination of Induced Radioactivity in Pepper by 10MeV Electron Irradiation. Mesurement of .BETA.-Ray with Liquid Scintillation Counter.

β-ray measurement was performed on 10 MeV electron-irradiated black pepper and white pepper with liquid scintillation counter in order to reconfirm the wholesomeness of irradiated foods and present unambiguous data to general consumers concerning about the induced radioactivity in the irradiated foods.In irradiated black pepper no radioactivity other than from natural source, un-irradiated one, was detected. But in irradiated white pepper, it was suggested that induced radioactivity might be detected if the detection method was more improved.

Reevaluation of induced radioactivity in 10MeV electron-irradiated pepper for public acceptance

Abstract In order to examine whether or not radioactivity could be produced in black pepper and white pepper with 10MeV electrons, the sample was irradiated with 10MeV electrons from a linear accelerator and its radioactivity was measured by gamma-ray spectrometry and beta-ray counting. The patterns of gamma-ray spectra showed that there was no difference between the irradiated and the non-irradiated samples, suggesting that the induced radioactivity in the irradiated sample was below the detection limit of its induced radioactivity. For further estimation, elemental composition was analyzed and photonuclear reactions which could produce radioactivity in the sample were investigated based on the data already published. Some photonuclear target nuclides in the list were spiked to the sample, being checked in the same way. Although short lived photonuclear products were observed, these radioactivities were found to decrease below the detection limit in a week. It is concluded that the induced radioactivity in the 10MeV electron-irradiated pepper and hence, its biological effect is far smaller than the natural radioactivity arising from 40K contained in the non-irradiated sample.

Mutagenicity test of gamma-irradiated humus in aqueous solution for the safety evaluation of irradiated water

Abstract Fulvic acid and humic acid which are difficult to be removed from water by ordinary purification processes were degraded by 60Co gamma-irradiation and the partially degraded samples were examined for the mutagenetic activity using Salmonella mutagenicity test. No mutagenic activity was detected even in 1000-fold concentrated samples. Addition of S9 mix did not stimulate mutagenicity either. These results revealed that 60Co gamma irradiation did not produce mutagenetic substances from the partially degraded fulvic and humic acids at detectable quantities.

Part II. Preservation of fruits wrapped with some kinds of plastic film and irradiation

さきに著者らは温州ミカンの貯蔵に対する電子線照射の影響を線型加速器を用いて予備的に行ない, その結果を報告した。今回はコッククロフト・ワルトン型電子線表面処理装置(三菱電機製)による低エネルギーの照射を行ない, 同時に照射後ミカンの腐敗菌による二次汚染を防ぐ目的で薄いプラスチックフィルムの包装効果を検討した。