DETECTION OF RADIATION TREATMENT OF SPICES AND HERBS OF ASIAN ORIGIN USING THERMOLUMINESCENCE OF MINERAL CONTAMINANTS

Eight types of spices and herbs or their mixtures of Asian origin have been investigated for detection of irradiation treatment using thermo luminescence (TL) of insoluble mineral contaminants adhering to the sa mples. These samples were irradiated by Co-60 gamma-rays (at absorbed doses 1, 5 and 10 kGy) as well as by 10-MeV electrons using an acceler ator (at a dose of 5.4 kGy). The integrated TL intensities of glow cur ves from the irradiated samples were found to be much higher than thos e from unirradiated samples. These results were normalized by administ ering a re-irradiation gamma-ray dose of 1 kGy and calculating the rat io of the integral of the first glow curve (of unirradiated or irradia ted samples) to that of the second glow curve (after re-irradiation). This ratio is less than 0.02 for all unirradiated samples and more tha n 0.3 for all irradiated samples (more than 1 for samples irradiated t o 5 kGy or at higher doses), thereby making discrimination between irr adiated and unirradiated samples possible. If one also compares the di fferent temperature regions of the glow-curve maxima of unirradiated a nd irradiated samples, unequivocal discrimination is achieved for thos e previously irradiated to doses equal to or greater than 1 kGy.