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Inactivation of selected microorganisms and properties of pulsed electric field processed milk

Michalac, S., Alvarez, V., Ji, T., Zhang, Q.H.
Journal of food processing and preservation 2003 v.27 no.2 pp. 137-151
skim milk, raw milk, Pseudomonas fluorescens, Lactococcus lactis, Bacillus cereus, food pathogens, food contamination, electrical treatment, electric current, dosage, flow, temperature, pasteurization, protein content, total solids, color, pH, particle size, density, electrical conductivity, viability, specific energy, viscosity, scanning electron microscopy
Raw skim milk and ultra-high-temperature (UHT) skim milk inoculated with Pseudomonas fluorescens, Lactococcus lactis and Bacillus cereus were processed by pulsed electric field (PEF) treatment. A continuous PEF bench scale system was set to deliver 35 kV/cm field strength with 64 pulses of bipolar square wave for 188 microsecond. The flow rate of milk was 1 mL/s. Milk temperature was raised to 52C and cooled to 22C during PEF treatment. Pasteurization at 73C for 30 s was used for comparison. Microbial inactivation and cell morphology were investigated. Analyses for protein, total solids, color, pH, particle size, density and electrical conductivity showed no significant effects (P > 0.05) in the PEF processed milk. PEF treatment accomplished a 0.3 to 3.0 log reduction of P. fluorescens, L. lactis and B. cereus in UHT milk and of total microorganisms in raw milk.