Sulfhydryl group content as an indicator of the radiation treatment of meat and fish for human consumption

A new biochemical procedure for the identification of irradiated pork meat, chicken and fish for doses ranging between few kilorad and several megarad is described. Spectrophotometric determination of the sulfhydryl content in irradiated and non-irradiated animal tissue using 6,6'-dithio-dinicotinic acid (DTDNA) is applied. Ionizing radiation causes a permanent loss of sulfhydryl groups in animal tissue such as meat or fish. The dose-effect relation for this radiation-induced decrease of the sulfhydryl content does not follow a single function for all different sorts of meat and fish. It may be correlated with a double exponential function, indicating that the sulfhydryl content of the animal tissues consists of two classes of widely different radiosensitivity. The most radiosensitive fraction of sulfhydryl groups represents approximately 23% - 50% of the total sulfhydryl content. The G-values of the radiation-induced oxidation of sulfhydryl groups in this fraction are estimated to be close to 23 molecules per 100 eV radiation energy absorbed by the animal tissues. For the fraction of the lower radiosensitivity the G-values reach 3 to 7 molecules per 100 eV. A mechanism confirming the observed radiation-chemical effects is suggested. Irradiation conditions, preparations of protein suspensions from meat, chicken and fish, spectrophotometric investigations and other experimental details are reported. (orig./MG)