부산대학교 도서관

Inactivation of Escherichia coli, E. coliO157:H7, and Staphylococcus aureusin liquid media by pulsed electric fields (PEF) was conducted at varying bacterial populations with and without sample agitation. A laboratory-scale PEF batch unit with a rectangular electric pulse was used, operating under the following conditions: 25 kV/cm (E. coli, E. coliO157:H7) and 30 kV/cm (S. aureus) electric field strengths, 1-μs pulse width, 1-Hz pulse repetition rate, and 20 to 350 pulses for all samples. Not surprisingly, bacterial inactivation (for all three strains) increased with increasing pulse number, achieving the highest reduction at 350 pulses. Log CFU per milliliter microbial inactivation increased commensurately with increasing bacterial population (P< 0.05) but only when samples were treated with more than 200 pulses. For example, when E. coliwas treated with 200 pulses at 105CFU/ml, inactivation was only 3.0 Log versus 4.8 Log at the 1010inoculation level. When E. coliO157:H7 was treated with 200 pulses at 105CFU/ml, inactivation was only 2.5 Log versus 4.6 Log at the 1010inoculation level. When S. aureuswas treated with 200 pulses at 106CFU/ml, inactivation was only 2.6 Log versus 4.8 Log at the 1010inoculation level. Inactivation of populations was also found to be statistically greater (P< 0.05) when liquid samples were agitated, in comparison to nonagitated samples. Because PEF inactivation activity is influenced by bacterial population and sample agitation, future studies should carefully consider these factors in experimental designs and/or scaled-up industry application.