Establishment of technological parameters for disinfestation of dried fruits

A study to determine the irradiation parameters for disinfestation of dried fruits: figs, pine nuts, raisins and walnuts, has been carried out in the UTR cobalt-60 facility. The dose distribution in the UTR boxes was measured. Low doses for disinfestation (150 Gy - 300 Gy) were studied, for the commercial practice simulation/validation higher doses were used (15 kGy - 20 kGy). The absorbed dose uniformity ratio (U = Dmax/Dmin) determined was 1.16 up to 1.33 for the dried fruits studied. Different dosimetric systems were tested. Low dose range dosimeters: reference standard Fricke dosimeter, routine dosimeters: Harwell YR Gammachrome and China PMMAYL dosimeter. High dose range dosimeters: routine dosimeters: Harwell Amber Perspex and Clear Perspex purchased at the local market. Label STERIN indicators of 125 Gy and of 300 Gy were assayed to establish a simple and direct process for verification, by customs inspectors, of a prior irradiation treatment. These indicators change their visual message if the threshold dose has been delivered. The performance of STERIN 125 and STERIN 300 suggested that these label indicators could properly be used for doses of 125 Gy and 300 Gy respectively, or higher than these ones. (author)