In order to eliminate the considerable loss of rice by insects, to protect the human body from toxin excreted by some microbes, and to promote the storage efficiency of rice by employing the irradiation, the following experiments were carried out.
Two varieties of rice, Paldal and Nongkwang polished and unpolished by the conventional methods and were packaged in polyethylene bags. After irradiating to the doses of 6-400 Krad of gamma-radiation from a Co-60 source the samples were stored at the room temperature 20℃ for 8 months.
The effects of radiation in terms of the removal of insects and microbes and the changes of chemical components (such as moisture, amylose, free sugar, and rancidity) were determined monthly from march to October during the storage.
1) Infestation of insects was greatly influeneed by the packaging materials used. There was no infestation in rice being packaged in a polyethylene bag, while as the rice packaged in a straw sack was infested in two months of the storage.
2) Some yeast and molds survived 400 K rad of radiation.
Sterilizing dose to inhibit reproduction and growth of microbes was presumed to be higher than 400 K rad. Yeast mainly were found on the surface of rice, but mold were embeded into rice kernels by mycelium.
3) Changes of moisture contents during storage was not affected by radiation but was by humidity of the storage room.
4) Amylose content in starch increased with increasing dose of radiation and with the length of storage time, indicating possible depolymerization of starch molecules.
5) Free reducing sugar content was not affected by radiation and decreased with storage time.
6) Rancidity also increased with does and storage time.
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