Pasteurization of raw skim milk by pulsed electric fields and antimicrobials
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This thesis is an investigation of the microbial inactivation in raw skim milk by pulsed electric field treatment and antimicrobials nisin and lysozyme. The innovative technology of using a high-voltage pulsed electric field (PEF) for pasteurizing milk offers advantages of low processing temperatures and low energy utilization, while inactivating pathogenic micororganisms especially when combined with other preservation methods. A 7.0 log reduction of microorganisms found in raw skim milk has been achieved through a combination of pulsed electric field treatment (80 kV/cm, 50 pulses), mild heat (52°C) and addition of the natural antimicrobial peptides nisin (3000 IU/ml) and lysozyme (100 [mu]g/ml). The combination of PEF, mild heat and antimicrobials resulted in a much higher microbial inactivation than the sum of the individual reductions achieved from each treatment alone, indicating synergy. Varying the pH from 6.7 to 5.0 had no effect on microbial inactivation.