Pulsed electric field preservation of liquid whey protein formulations - Influence of process parameters, pH, and protein content on the inactivation of Listeria innocua and the retention of bioactive ingredients

gentle preservation concept for heat sensitive protein formulations based on the application of pulsed electric fields (PEF) was developed. The inactivation of L. innocua in 2 and 10% whey protein isolate (WPI) formulations at two different pH levels (4 and 7), with inlet temperatures of 20-40 degrees C, and a maximum outlet temperature of 58 degrees C was studied, applying different PEF treatment conditions. Results showed an inactivation of up to 6.51 log(10) cycles of L. innocua with limited or no impact on the concentration of selected heat sensitive bioactives from their initial values before PEF treatment. The efficiency of the inactivation decreased with increasing protein concentrations and pH values. The differentiation of thermal and electric field effects revealed a maximum of 1 log(10) cycle of thermal inactivation at the highest PEF treatment intensity. The traditional D-value concept was successfully transferred to model the PEF inactivation kinetics.