Bacterial inactivation in whole milk using pulsed electric field processing.

摘要

Inactivation of Gram-negative and Gram-positive bacteria in whole milk by pulsed electric field (PEF) processing with pre-heating of milk and stepwise intermediate cooling was compared with thermal pasteurisation. Electric field strengths of 18-28 kV cm-1 for 17-235 mus were applied to milk at different temperatures for 24 s. PEF treatment at 4 degrees C did not reduce bacterial numbers, but the effectiveness increased with increasing temperature. PEF treatments at 22-28 kV cm-1 for 17-101 mus at 50 degrees C gave a 5-6 log reduction, below the detection limit for Pseudomonas aeruginosa, while Escherichia coli, Staphylococcus aureus and Listeria innocua were reduced to below the detection limit at 55 degrees C. Gram-negative bacteria were less resistant to PEF than Gram-positive bacteria. PEF treatment with stepwise intermediate cooling after pre-heating at 55 degrees C for 24 s at a flow rate of 4.2 mL s-1 has the potential to pasteurise whole milk