Abstract: Electron spin resonance (ESR) spectroscopy is an effective method to identify irradiated dried nuts. In this experiment, ESR spectral characteristics of pistachio, walnut and longan were determined and the effect of drying temperature of samples on ESR signal intensity was also explored. The results showed that ESR signal intensity of characteristic peak was positively correlated with irradiation dose, and the detection limit of irradiation was 0.5 kGy. However, during further drying, the optimal temperature was 40 ℃ for pistachio and walnut, and 55 ℃ for longan. ESR signal intensity of characteristic peak was also affected by microwave power. The optimal microwave power were 0.59, 0.37 mW and 0.24 mW for pistachio, walnut and longan, respectively. Therefore, ESR characteristic peak can qualitatively determine the irradiation of dried nuts, which can provide a theoretical basis for detecting the dried nuts by ESR.

Key words: electron spin resonance, dried nuts, irradiated food