Luminescence characteristics for identifying irradiated black soybeans.
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. 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. 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. PSL and TL are effective screening and reference methods for distinguishing gamma ray or electron beam irradiated black soybeans from non-irradiated black soybeans.