• Korean Journal of Fisheries and Aquatic Sciences
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• v.13 no.4
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• pp.163-171
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• 1980

Recently, Bacillus has been identified as one of food poisoning bacteria especially in products of cereal foods in foreign countries. Therefore, the quantitative distribution of Bacillus cereus in market foods, its physiological characteristics, growth rate by temperature and heat resistance of its spore were examined. Thirty two samples of cooked rice, 20 samples of kimbab(cooked rice rolled with laver), 23 samples of rice cake, 13 samples of rice ana 13 samples of barley were collected from restaurents and food stores in Busan, Korea during the period from May to November in 1980. Forty samples of 101 samples submitted to the test appeared positive for Bacillus cereus showing abut $40\%$ in detection ratio. Detection ratio of Bacillus cereus was higher than $50\%$ in barley and rice, and about $30\%$ in rice products. Average Bacillus cereus content of in the samples was $2.6\times10^6/g$ in cooked rice, $2.3\times10^6/g$in kimbab, $4.9\times10^4/g$ in rice cake while that in rice and barley was about $10^3/g$. The result of biochemical tests of the bacterium was $100\%$ positive in catalase, egg yolk reaction, gelatin hydrolysis and glucose fermentation, $100\%$ negative in xylose, arabinose and mannitol oxidation, about $90\%$ positive in acetoin production, $80.0\%$ positive in nitrate reduction and citrate utilization and $55.0\%$ positive in starch hydrolysis test. Isolation ratio of Bacillus ceresus which showed haemolysis positive and starch hydrolysis negative results, was about $38\%$ in 40 strains examined. It is known that those strains has a close relation to food poisoning accident. Growth rate and generation time of Bacillus cereus isolated from the cooked rice were $0.34hr^{-1},\;2.02hr\;at\;20^{\circ}C,\;0.73hr^{-1},\;0.95hr\;at\;30^{\circ}C\;and\;0.49hr^{-1},\;1.44\;hr\;at\;40^{\circ}C$ respectively. Heat resistance value of Bacillus cereus spores suspended in phosphate buffer solution was $D_{90}=29.0min,\;D_{95}=8.7min,\;D_{98}=3.7\;min\;and\;D_{101}=2.3\;min(z=10.5)$.