In this study, the effects of irradiation on the Senna (Casia acutifolia) leaves exposed to gamma rays at various doses were investigated by means of Electron Spin Resonance (ESR) technique. Before irradiation a broad and asymmetric signal having g value of 2.0038 which was attributed to quinone radicals were observed. In the irradiated samples, a symmetric singlet signal with the g value of 2.0050 was detected and it was determined as radiation sensitive. According to isochronal annealing and fading studies it was shown that this signal was formed of short and long-lived two radicals. Because one of the components of the singlet signal in irradiated samples was quite stable at room temperature, so it was suggested to be used in irradiated food detection studies. It was revealed out by kinetic studies that the thermal responses of the singlet signals in natural and irradiated samples are different, thus it was emphasized that doing kinetic measurements for irradiated food detection was quite important, especially when the satellite signals could not be observed. Furthermore, by microbiological analysis, in order to investigate the effects of radiation on microorganisms in samples, microbial loads of irradiated samples at different doses were examined, and the lowest irradiation doses to inactive the microorganisms found in the natural sample were determined.