Inactivation of Bacillus subtilis spores on the surface of small spheres using low-pressure dielectric barrier discharge
2020
Tanino, Takanori | Matsui, Masayoshi | Uehara, Kensuke | Ohshima, Takayuki
Inactivation of Bacillus subtilis spores on the surface of small spheres by dielectric barrier discharge (DBD) using relatively low AC high voltage (<10 kV0-p) for practical applications in the sterilization of small dried food was investigated. In this study the 6 and 10 mm gap distances were employed to place small dried foods inside the DBD, but a gap distance of more than 3 mm generally did not generate DBD at this applied voltage and atmospheric pressure. Therefore, the pressure was reduced to generate DBD and the relationship between discharge area rate and pressure was investigated using discharge area rate as the index. Low-pressure DBD (LPDBD) at 6 and 10 mm gap distances showed the maximum discharge area rates of 28% and 25% at 50 and 30 kPa, respectively. After 4 min treatment, B. subtilis spores on the surface of glass beads as the model of a small dried food were inactivated and the survival ratio decreased to 3.6 × 10−4 after the LPDBD treatment at 10 mm gap distance, and no viable cells were detected after the LPDBD treatment at 6 mm gap distance. Moreover, the humidification of the atmosphere was effective in improving the inactivation efficiency of LPDBD treatment, with which, B. subtilis spores were inactivated within 2 min of LPDBD treatment at 6 mm gap distance.
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