Effect of High Intensity Pulsed Electric Fields on Microbial Inactivation of Cow Milk

摘要

High Intensity Pulsed Electric Field (HIPEF) processing of food is a nonthermal method alternative to traditional thermal method. Two HIPEF apparatuses were designed and constructed in this experiment for generating bipolar exponential decay and square wave forms. The central components of the pulse generator consisted of a treatment chamber, pulse driver, cooling system flow meter and a microcontroller. Two coaxial and upgraded cylindrical chambers were made. Different electric fields strength (18-30 kv cm-1), pulse no. (200-1500 for coaxial chamber and 5-120 for the upgraded cylindrical chamber) were applied at various pulse width (0.5-4 μs) and temperatures (25-53°C). The Iranian standard conventional plate count method was employed for microbial count as colony forming unit (CFU mL-1). In all raw cow milk samples testing the microbial counts were reduced significantly. The upgraded cylindrical chamber was more effective than the coaxial chamber. Microbial count reduced 5.5±1.1 times following treating milk samples by the cylindrical chamber and square form bipolar pulses. This reduction for the exponential pulses was 1.8±0.08 times. No changes in milk constituents including Solid Not Fat (SNF), protein and fat contents were observed. For commercialization the milk processing by this system (HIPEF) more researches and financial supports are needed.