| Budget Amount *help |
¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1999: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1998: ¥500,000 (Direct Cost: ¥500,000)
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| Research Abstract |
In order to establish a method for studying the growth and toxin production by Clostridium botulinum in modified atmosphere packaged (MAP) condition, agar surface system using Trypticase Soy Agar (TSA) plate in which the pH was adjusted to equal that in COィイD22ィエD2 atmospheres was employed. Results showed that this system could be used for estimating the effect of headspace gas on the bacterial growth (Escherichia coil and Staphylococcus aureus) on the surface of (TSA) packaged with various COィイD22ィエD2 partial pressures (0, 20, 40, 60, 80, 100%, balance NィイD22ィエD2).
Using the agar surface system described above, the effect of COィイD22ィエD2 on spore germination and vegetative cell growth of Clostridinium botulinum was investigated at various concentration (COィイD22ィエD2 0-100%,remainder NィイD22ィエD2) and temperatures (15℃, 5℃). At 15℃, the number of spore which could germinate and outgrow was significantly enhanced under a controlled COィイD22ィエD2 gas atmosphere as compared to NィイD22ィエD2 gas atm
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osphere (100%) regardless of their concentrations. The highest number of germinating spore was obtained with COィイD22ィエD2 concentration of 20%, as followed by 40%, 60%, 80%, and 100% in this order. Storage at 5℃ under COィイD22ィエD2 atmosphere significantly reduced the number of spore which could germinate. Under NィイD22ィエD2 atmosphere the number of spore did not differ from initial levels and remained unchanged for remainder of the storage period. Hence it was suggested that COィイD22ィエD2 not only inhibit germination but also promote the death of C. botulinum type E at 5 or 0 ℃ on the agar media employed.These findings on the adverse effect of COィイD22ィエD2 on spore germination with decreasing temperatures suggest extreme importance of proper storage temperatures for controlled COィイD22ィエD2 MAP (Modified Atmosphere Packaged) foods at all point of the food chain.
Finally, the growth and toxin production of Clostriclium botulinum type E inoculated on fresh fish fillets (jack mackerel and yellowtail) packaged under carbon dioxide (COィイD22ィエD2 40%, NィイD22ィエD2 60%) and NィイD22ィエD2(NィイD22ィエD2 100%) controlled gas atmosphere were investigated at two abusive temperatures (10℃, 30℃) for short period of time. At 10℃, the growth of C. botulunum was slower in samples initially packaged with 40% COィイD22ィエD2 than those packaged with 100% NィイD22ィエD2 in Jack Mckerel samples, indicating a potentially lower risk in COィイD22ィエD2 atmosphere than in NィイD22ィエD2 atmosphere at 10℃. No increase in the C. botulinum type E population on jack mackerel was noted regardless of the type of packaging within 6h at 30℃. At prolonged period of storage at 10℃, all samples were spoiled before they became toxic, regardless of atmospheres. The results suggested that the botulinal risk in MAP fish in Japanese distribution system is minimal even under abusive conditions. Less
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