Comparison of radiation-induced hydrocarbons for the identification of irradiated perilla and sesame seeds of different origins.
Perilla and sesame seeds, a rich source of energy, are commonly utilized in different forms in many countries. During the post-harvest period, they are contaminated with insects as well as microbes that may have importance for keeping quality and quarantine, and thus they can be treated with ionizing radiation for insect disinfestation and microbial decontamination. Reliable and routine methods to identify whether or not a food has been irradiated are needed to help consumers' understanding of irradiated food and promote international trade. In the present study, fat-derived hydrocarbons from irradiated perilla seeds and sesame seeds of Korean and Chinese origin were analyzed in order to identify irradiation treatment by comparing their properties during the post-irradiation period. Gas chromatographic-mass spectrometric analysis showed that several saturated hydrocarbons, such as tetradecane, pentadecane, hexadecane and heptadecane, were found in the non-irradiated control samples, while four radiation-induced unsaturated hydrocarbons (R(2) = 0.647-0.997), such as 1,7,10-hexadecatriene (C(16:3)), 1,7-hexadecadiene (C(16:2)), 6,9-heptadecadiene (C(17:2)) and 8-heptadecene (C(17:1)), were detected in all irradiated samples at 0.5 kGy or higher, with variations according to sample and origin. Concentrations of all hydrocarbons were reduced during storage and could not be detected in 0.5 kGy irradiated Chinese sample of either seed after 8 months. Radiation-induced hydrocarbons (C(16:3, 16:2, 17:2, 17:1)) could be used as markers to identify irradiated perilla and sesame seeds of both Korean and Chinese origin at 1 kGy or higher for 8 months' storage at room temperature.