Reduction of bacterial counts and inactivation of enzymes in bovine whole milk using pulsed electric fields

Abstract

Bacterial count reduction and enzyme inactivation in bovine whole milk by pulsed electric field (PEF) processing combined with pre-heating and intermediate cooling was compared with that induced by thermal treatments (maximum of 63 °C for 30 min and 73 °C for 15 s). Milk was pre-heated to 55 °C for 24 s and PEF-treated in continuous mode at electric field intensities of 15.9–26.2 kV cm−1 for 17–101 μs. PEF treatments reduced the number of inoculated (8.3 log cfu mL−1) Escherichia coli and Listeria innocua to less than 2 log cfu mL−1. PEF treatments at 20.7–26.2 kV cm−1 reduced the total plate count and indigenous alkaline phosphatase activity to a level similar to that measured following thermal treatments. Treatment at 26.1 kV cm−1 for 34 μs, combined with pre-heating, reduced the activity of plasmin, xanthine oxidase and lipolysable fat by 12%, 32% and 82%, respectively, compared with raw milk.