γ-Irradiation of Thai Rice and Microflora:Study on Radio-pasteurization, Part. II

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In the previous paper, we reported radio-sterilizing effect and change of microflora of unpolished rice harvested in Japan, and polished rice imported from Spain. They were irradiated in order to store a long period. In this investigation, Thai rice unfumigated with methylbromide was used as a sample.<BR>(1) The main microflora of unirradiated Thai rice was mainly occupied by secondary contaminated microorganisms such as Bacillus megaterium, B.cereus, B.subtilis, Brevibacterium and Micrococus which were peculiar to long-time-stored polished rice, and also Actinomycetes was isolated at a considerable amount. Fluorescent Pseudomonas and Chromogenic Pseudomonas which are main microorganisms of new rice, were not isolated.<BR>(2) When the total dose on Thai rice reached between 0.1 and 0.2 MR, a rapid decrease of the number of survival microorganisms, as can be seen in case of new rice reported in our previous paper, was not observed. Bacillus and Actinomycetes were main survivors at the dose of more than 0.2 MR, but Bacillus was more resistant to irradiation than Actinomycetes.<BR>(3) Moulds found, mainly Aspergillus, were much less than Bacteria. Some Penicillium were also isolated. Aspergillus and Penicillium were sterilized at the dose between 0.3 MR and 0.4 MR.<BR>(4) Polyethylene bag was better than craft paper bag for the purpose of longer storage of polished rice.
日本食品照射研究協議会の論文