Detection of irradiated powdered foods using photostimulated luminescence method

Photostimulated luminescence (PSL) method provides a rapid and markedly sensitive technique to detect of any irradiated food that contain minerals. This method is also convenient as a first screening means in comparison with thermoluminescence (TL) method which requires separating minerals from the food materials. The present study reports the results of PSL measurements for both irradiated and non-irradiated powdered dry leaf vegetable obtained with the prototype of PSL system developed by our groups. This PSL system consists of pulsed Infra-Red (IR) source for photostimulation, single photon counting system for high sensitive detection of luminescence, and computer for data treatments. The PSL intensity of the leaf vegetable increased with increase of gamma radiation dose and show a linear relationship up to a dose of 1kGy. The PSL intensities after four months of storage under light shielding following gamma irradiation (0.49-3.1kGy) decreased to less than half of initial intensities. The PSL intensities of those decreased rapidly for 60 seconds and reached a steady level close to intensity of non-irradiated sample after 300 seconds following photostimulation. We used the information on the shape and slope of PSL intensity curve as a criteria to discriminate whether irradiated foods or not, and possible to detect the irradiation history of food irradiated with a 0.49kGy dose after four months of storage.