Effect of pulsed electric fields on microbial inactivation and gelling properties of porcine blood plasma

The effect of pulsed electric fields (PEF) on the inactivation of inoculated Pseudomonas (P.) fragi, Escherichia (E.) coli (K12) and Staphylococcus (S.) xylosus as well as on the total aerobic plate count (TPC) of porcine blood plasma was investigated. Furthermore, the impact of PEF on gel strength and solubility was analysed. Inoculated plasma samples were PEF treated at an initial temperature of 30 degrees C, electric field strength between 9 and 13 kV/cm and a specific energy input in a range of 40 to 182 kJ/kg for total treatment times between 35 mu s and 233 mu s. Increased specific energy input led to increased microbial inactivation, but then decrease in soluble protein and gel strength occurred. To avoid undesired protein denaturation, energy input should not exceed 120 kJ/kg. Considering these processing conditions an inactivation of 3.0 +/- 0.4 log steps for the total plate count was proven (p < 0.001). Inoculated E. coli K12 and P. fragi could be reduced below the detection limit (p < 0.0001) and for at least 3 log steps (p < 0.0001), respectively. S. xylosus was the most PEF resistant germ and for sufficient inactivation higher energy input was needed which resulted in outlet temperatures above 60 degrees C (p < 0.01). Industrial relevance: The treatment of blood plasma with pulsed electric fields (PEF) is in principle a suitable method for reducing the total plate count, Pseudomonas fragi, Escherichia coli and Staphylococcus xylosus in porcine blood plasma. Inactivation is limited by the specific energy input which should not exceed 120 kJ/kg at start temperatures of 30 degrees C to avoid undesired protein denaturation. Improved microbiological quality of PEF-treated blood plasma enables enhanced utilisation possibilities and allows extended storage times. (C) 2014 Elsevier Ltd. All rights reserved.