Application of pulsed electric fields with square wave pulse to milk inoculated with E. coli, P. fluorescens, and B. stearothermophilus

Ultra-high temperature (UHT) processed full fat milk inoculated with Escherichia coli, Pseudomonas fluorescens, and Bacillus stearothermophilus was exposed to 30-60 kV/cm square wave pulsed electric field (PEF) with 1 μsec pulse width, and 26-210 μsec treatment time in a continuous PEF treatment system. Eight log reduction was obtained for E. coli and P fluorescens and 3 logs reduced for B. stearothermophilus under PEF treatment conditions of 210 μsec treatment time, 60 kV/cm pulse intensity at 50°C. There was no significant change in pH and titration acidity of milk after PEF treatment. The electrical energy required to achieve 8 log reduction for E.coli and P fluorescens was estimated to be about 0.74 kJ/L.