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KMID : 1007520110200030751
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Food Science and Biotechnology
2011 Volume.20 No. 3 p.751 ~ p.757
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Optimization and Evaluation of Heat-shock Condition for Spore Enumeration Being Used in Thermal-process Verification: Differential Responses of Spores and Vegetative Cells of Clostridium sporogenes to Heat Shock
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Byun Bo-Young
Cho Hong-Yon
Hwang Han-Joon
Mah Jae-Hyung
Liu Yanhong
Tang Juming
Kang Dong-Hyun
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Abstract
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To evaluate a heat-shock condition for the enumeration of Clostridium sporogenes spores, a surrogate for C. botulinum spores, we examined the heat tolerance of C. sporogenes spores and vegetative cells exposed to a heat shock at 90oC. From the D values of the spores determined in the temperature range of 113-121oC, z value (±SD) and D90°C value were estimated to be 10.16±0.90oC and 1,071.52 min, respectively, and the inactivation rates were predicted to be only approximately 2% at 90oC for up to 10 min. Meanwhile, the viable count of spores was significantly higher when activated under a heat-shock condition of 90oC for over 9 min than those activated for shorter time periods. The heat tolerance of vegetative cells was extremely low, showing a D90°C value (±SD) of 0.21±0.01 min. Finally, 3 different heat-shock conditions were compared: 70oC for 30 min, 80oC for 20 min, and 90oC for 10 min, and the experimental comparative data showed no significant differences in viable spore counts. Consequently, these results support that the heat-shock treatment at 90oC for 10 min is suitable to activate spores and to inactivate vegetative cells of C. sporogenes.
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KEYWORD
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Clostridium sporogenes, spore, vegetative cell, enumeration, heat shock
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