Studies on detection and dosimetry of irradiated food by thermoluminescence (TL) and electron paramagnetic resonance (EPR) spectroscopy

Abstract

Food irradiation is the treatment of food by ionizing radiation. The need for reliable and routine tests to determine whether or not food has been irradiated has arisen as a result of the progress made in commercialization of the food irradiation technology, increased international trade in irradiated foods, and consumer demand for clear labeling of the treated food. On the other hand, the effectiveness of processing of food by ionizing radiation depends on proper delivery of absorbed dose and its reliable measurement. External influences such as the temperatures of dose measurement, accuracy in a rather narrow dose range are the other problems that confront dosimetry. An attempt has been made to study the identification methodology of irradiated foods with commercially relevant doses based on physical methods namely, Thermoluminescence (TL) measurements and Electron Paramagnetic Resonance (EPR) spectroscopy. In case of measurements of absorbed dose, investigations were carried out to understand the mechanism of modified CaSO4 based thermoluminescence phosphors by TL-EPR correlation studies and to find out the efficacy of the phosphor as a food irradiation dosimeter. In case of identification of irradiated food, foods were chosen from all the groups of different purposes of irradiation namely sprout inhibition, insect disinfestations, microbial decontamination etc. In many cases both the techniques were employed to give a complete verdict about irradiation. EPR spectroscopy determined various paramagnetic centres namely carbohydrate radical, cellulosic radical and axially symmetric CO2 radical ion as the markers of radiation treatment. EPR spectral behavior, relaxation characteristics, and thermal behavior of the radical emerged as useful tools to detect irradiation even after prolonged storage. TL measurements of the isolated minerals from the foods were successfully employed to detect a wide spectrum of irradiated food.