INACTIVATION OF ESCHERICHIA-COLI AND STAPHYLOCOCCUS-AUREUS IN MODEL FOODS BY PULSED ELECTRIC-FIELD TECHNOLOGY

Inactivation of microorganisms exposed to high-voltage pulsed electric fields is a promising non-thermal food preservation technology. This paper demonstrates and validates the inactivation of Escherichia coli, a Gram-negative bacterium and Staphylococcus aureus, a Gram-positive bacterium, subjected to high-voltage electric field pulses. A four-log cycle reduction in microbial population is achieved in model foods such as simulated milk ultrafiltrate (SMUF) with a peak electric field strength of 16 kV/cm and 60 pulses with a pulse width ranging between 200 and 300 mu s. The temperature of the cell suspension was kept below the lethal temperature, demonstrating that inactivation is not due to thermal effects induced by the pulses of high-voltage electricity. Thermal food preservation causes undesirable changes in the physical character, quality and nutrient content of foods. Non-thermal preservation techniques minimize the undesirable changes in foods. A comparison between the inactivation of microorganisms by high-voltage pulsed electric fields and thermal methods of food preservation is also discussed.