Abstract
The spices are commonly required food in modern life. The people is rising awareness of food safety including the safety of radiation irradiated food. The sterilization methods using ionizing radiation for spices has been frequently used in Taiwan and abroad. The aims of using high doses of ionizing radiation to irradiate spices are that effectively achieve sterilization of spices. Compared to other sterilization methods, the radiation sterilization has the advantages of easy, fast, relatively non-perishable and non-chemical residue. Although the gamma irradiated products have been commercially used in Taiwan, anyway, identification of radiation sterilization food has not been set yet. The exported gamma irradiated food must meet strict control by the import countries. For example, Japan, after the Fukushima incident, is strictly control the imported radiation irradiated food. The study designed to follow the report of International Atomic Energy Agency (IAEA) that gives the recommendation regarding the criteria of food irradiations. In this research, Co-60 was selected as the radiation source of sterilization applications. The spices are common used and most frequently irradiated by radiation for sterilization in Taiwan. Eleven investigated samples listed below in sequence: Five-Spice powder, Cinnamon powder, Curry powder, Chili powder, Star aniseed powder, Coriander seed, Herb powder, Lemon grass, Cassia powder, Fennel powder, Black Pepper. In addition, the characteristic of quartz tube is also assessed in the experiments. According to the principle of EPR (Electron paramagnetic resonance), irradiated samples will produce unpaired electron products which include the free radicals. The number of unpaired electrons could be converted to form the signals of EPR. The signals could be analyzed by parameters of either Peak-to-peak value or Area of curve (AOC). With analysis of Peak-to-peak or Area of curve, unpaired electron concentration related to free radicals of the spices after radiation exposure is proportion to radiation dose. EPR signal of spices is proportion to the number of free radical. EPR signal decay with time, and with different decay characteristic dependent on the types of spices. By the method of this research, whether the spices through radiation sterilization or not can successfully be determined. In addition, the study found that pure quartz tubes, the container of spice samples while perform EPR test, will not produce EPR signals before irradiation, but it will produced large amounts of EPR signals after radiation exposure. This research has analyzed irradiated quartz tubes which the EPR signals were stable. Key Word：Electron paramagnetic resonance spectroscopy (EPR), Sterilization of irradiation, Spices, Quartz tube, peak-to-peak value.