Luminescence characteristics for identifying irradiated black soybeans.

PURPOSE: Considering the commercial use of food irradiation and the prevalence of international trade of irradiated food and agricultural commodities, black soybeans originating from China or Korea were irradiated at 0-5 kGy. Photostimulated luminescence (PSL) and thermoluminescence (TL) were investigated for their ability to identify characteristics that would distinguish irradiated from non-irradiated samples. MATERIALS AND METHODS: Dried black soybeans [Glycine max (L.) Merr.] were irradiated using a Co-60 gamma irradiator or an electron-beam accelerator and then analysed by PSL and TL. RESULTS: PSL photon counts were higher in irradiated samples than in non-irradiated ones and increased with applied doses, making it possible to distinguish irradiated from non-irradiated samples. The TL analysis revealed glow curves (TL₁) with low intensity for non-irradiated samples but a higher intensity (approximately 200°C) for irradiated samples, showing increased intensities with radiation dose. The minerals were re-irradiated at 1 kGy and the second TL glow curve (TL₂) was measured. Based on the calculated TL ratios (TL₁/TL₂) and the shape of TL₁ glow curves, the irradiated samples could be distinguished from non-irradiated ones. CONCLUSIONS: PSL and TL are effective screening and reference methods for distinguishing gamma ray or electron beam irradiated black soybeans from non-irradiated black soybeans.