engleski

Identification of irradiated foods: Post-irradiation dose estimate in irradiated dry egg

Radiation-induced chemical changes in foods are generally very small at the usual processing doses. Nevertheless, a sensitive and reproducible spectrophotometric method of lipid hydroperoxides (LOOH) determination based on the formation of feric thiocyanate, as modified in our laboratory1, could be applied for positive identification of irradiation treatment2. The representatives of various classes of lipid containing foods: egg and milk powder, soya flour and haselnuts were investigated3. The decay of radiation-induced LOOH in irradiated egg powder could be described by dispersive kinetics. After a six months’ storage it was still possible to unambigously identify LOOH in samples irradiated with the processing dose of 2 kGy2, 3. The level of LOOH attained by that time was still above the average level of indigeneous LOOH in unirradiated commercial egg samples, supplied by two producers (0.110 &plusmn ; 0.08 mmol/kgL). Another prominent feature of radiation peroxidation of egg powder has been shown to be suitable for the identification purpose – the inhibition dose, Dinh. Irradiation of egg powder in the presence of air revealed an initially slow increase of LOOH with dose, caused by an inherent antioxidative capacity, followed by a faster linear increase after the breakpoint inhibition dose. Dinh did not depend on dose rate spanning three orders of magnitude (about 4, 0.4 and 0.04 Gy/s). In the commercial samples the value of Dinh = 2.2 &plusmn ; 0.8 kGy was obtained. One would expect almost complete destruction of antioxidative properties of egg powder when treatment dose was equal to or exeeded the inhibition dose. However, the reirradiation of samples which had been originaly irradiated with 2 kGy and kept in dark at room temp. revealed a reduced Dinh = 1.0 &plusmn ; 0.1 kGy. In samples irradiated with 4 kGy and kept under the same conditions, the reduction of Dinh to 0.5 kGy occurred on by reirradiation. Besides identification, this offers a possibillity for the estimation of the original irradiation dose. 1. 1. B. Mihaljević, B. Katušin-Ražem, D. Ražem: Free Radic. Biol. Med., 21 (1996) 53-63. 2. B. Katušin-Ražem, B. Mihaljević, D. Ražem: Nature, 345 (1990) 584. 3. B. Katušin-Ražem, B. Mihaljević and D. Ražem: Detection of irradiation treatment of foods based on lipid hydroperoxidation, submitted.

irradiation; food; identification; dose estimation

nije evidentirano