Thermoluminescence Analysis for Detection of Irradiated Food-Luminescence Characteristics of Minerals for Different Types of Radiation and Radiation Doses

Thermoluminescence analysis is used to detect radiation processing of foods which are contaminated with sand or dust. Silicate minerals are isolated, their radiation-induced luminescence is measured and compared to the thermoluminescence from a second measurement after exposure to a defined radiation dose (normalization). In the present study, the mineral mixture `sandʹ and its main components feldspar and quartz were investigated for their thermoluminescence behaviour using different types of radiation, in order to determine adequate radiation sources for the purpose of normalization. The material was irradiated with types of ionizing radiation commonly used for commercial food irradiation, i.e. accelerated electrons with beam energies of 5 MeV as well as 10 MeV, and60Co- -rays. After thermoluminescence measurements, samples were re-irradiated using either accelerated electrons with beam energies of 2 MeV, 5 MeV or 10 MeV, or60Co- -rays,90Sr- -rays or ultraviolet rays (200-280 nm). Evaluation of the first and corresponding second glow curve revealed that their shapes depend on the type of minerals in the mixture. The second radiation treatment (normalization) is satisfactory when accelerated electrons (2, 5 and 10 MeV) as well as60Co- -rays and90Sr- -rays are employed. Normalization with ultraviolet rays, however, has only a limited range of use.