Thermal effect on liquid sterilization using intense pulsed electric fields

This paper describes liquid sterilization using intense pulse electric fields (iPEF) combined with mild thermal treatment. A 600 ns-long mono-polar rectangular high voltage pulse was repetitively applied to a 4 mm-gap, parallel plain electrode set in an iPEF application cell. Carboxymethyl cellulose (CMC) solution including Enterobactor aerogenes (E. aerogenes) was exposed to moderate heat (<; 55°C) before and after exposure to tens of 50 kV/cm pulses. Temperatures of the pre- and post-treatment heaters were controlled independently. The influence of post-treatment temperature kept at 55°C for 2 minutes was evaluated with pre-treatment temperature fixed at 40°C. Results indicate a synergistic effect, with bacterial population reduced by 6.6 log10 under the condition of 55°C and 35 pulses, which is sufficient for food processing. Sterilization potency depends not only on pulse number but also on thermal treatment temperature. Bacterial death is considered to be caused by heat influx due to PEF-induced membrane disintegration.