Inter-Laboratory study to define the temperature interval for a thermoluminescence heating unit used to identify irradiated food

EN 1788:2001 suggests defining the temperature range for the thermoluminescence (TL) heating unit to calculate the TL ratio (TL1/TL2). In the present study, practical temperature ranges were established by using well-characterized lithium fluoride (LiF, TLD-100®) at 4 different research institutes in Korea. Temperature ranges differed according to models of TLD heating unit, which were wide in the case of RISO (160–249°C) as compared with Harshaw (155–232°C) TLD readers. The silicate minerals separated from irradiated turmeric samples were measured to check these intervals on a practical basis. The X-ray diffraction (XRD) analysis of separated minerals showed that quartz and feldspar minerals were the main source of well-characterized TL glow curve following irradiation. The TL glow peaks from the separated minerals were narrower in Harshaw than RISO TLD readers. The TL ratios determined after re-irradiation (1 kGy) for the tested minerals, using the pre-defined temperature intervals, provided the satisfactory results.