Factors influencing the yield of free radicals in irradiated chicken bones

Summary The exposure of foodstuffs containing bone or other calcified tissue to a dose of ionizing radiation results in the formation of long lived free radicals which give rise to characteristic ESR signals. The presence of this signal provides clear evidence that the sample has been irradiated. In order to determine the radiation dose by post‐irradiation calibration, it is necessary to consider factors that might influence the radical yield and to allow for the stability of the radicals under likely conditions of storage. Using chicken bone we have shown that the yield is influenced by the nature of the bone, temperature of irradiation, and gaseous atmosphere, although not by dose rate, water content, or type of radiation. Cooking before irradiation greatly enhances the subsequent yield of radicals, while cooking after irradiation causes little or no destruction of the radiation‐induced radicals, which also appear to be unaffected by length and conditions of storage.