Identification of X-ray-irradiated hazelnuts by electron spin resonance (ESR) spectroscopy

Food irradiation is used to preserve food from pathogenic microorganisms, deterioration and to extend shelf life. The EU legislation states that any irradiated food or food ingredients must be labeled with the word "irradiated". The ESR spectroscopy is a powerful tool to enhance official checks; hence, it has been used to detect irradiated hazelnuts. The results from the ESR studies on hazelnuts before and after X-ray irradiation are reported. Before irradiation hazelnuts exhibit one singlet ESR line characterized with a g-factor of 2.0046 +/- 0.0006. After irradiation, a typical "cellulose-like" triplet ESR spectrum appears. To investigate the radio-induced free radical stability, the peak-to-peak amplitude of the ESR satellite signals was considered. Fading measurements indicate that the intensity of the ESR spectra of hazelnuts is reduced to about 70% after 30 days. In addition, the microwave power behavior and a dose-response relation were investigated. The study confirmed the applicability of ESR technique to detect irradiated hazelnuts also when a long time after treatment was passed.