Use of Thermoluminescence Technique for the Detection of Irradiated Spices

Black pepper and cumin samples were analyzed for identification of irradiation treatment Thermoluminescence (TL) signals of irradiated and unirradiated spices were due to inorganic dust particles adhering to the surfaces. All X-ray diffraction - characterized dust samples revealed the presence of at least 2 common minerals; quartz and feldspars. The samples were irradiated by 60Co gamma - rays at 1, 3, 5 and 10 kGy. Results indicated a clear detectable difference in the shape of glow curves from irradiated and unirradiated samples, and glow curves from irradiated ones with a characteristic shape. The TL effect due to radiation treatment differs from spice to spice and package to package. The TL integrated areas of irradiated spices were higher than their controls. Irradiation can be detected more reliably by comparing the first (original =TL1) glow curve with the reirradiated one (TL2). The ratio of the area of the first glow curve (before re-irradiation) to the second glow curve (after re-irradierion) was> 1.30 for all irradiated samples and < 0.01 for unirradiated samples. Quantitative estimation of absorbed dose can be achieved by re-irradiation and extrapolation to zero signal. Based on the observations made it is possible to distinguish irradiated black pepper and cumin after 365 days post-irradiation.