Effects of Pulsed Electric Field Processing on Quality Characteristics and Microbial Inactivation of Soymilk

Effects of pulsed electric fields (PEF) on quality characteristics and microbial inactivation of soymilk were studied with different PEF parameters. PEF did not affect significantly the values of pH, a (an indicator of redness ranging from -a to +a, -a = green, +a = red) and electric conductivity. The values of L (white if LaEuro parts per thousand= 100, black if LaEuro parts per thousand= 0) increased slightly, whereas values of viscosity and b (an indicator of yellowness ranging from -b to +b, -b = blue, +b = yellow) decreased slightly as PEF time increased from 0 to 547 mu s. Cysteine, tyrosine, phenylalanine, and serine reduced with the increase of PEF time. The relative activities of soybean lipoxygenase (SLOX) decreased with PEF time increasing from 0 to 1,036 mu s. When PEF time and strength increased, the inactivation of Escherichia coli and Staphylococus aureus increased significantly (p < 0.05), achieving a maximum of 5.20 and 3.51 log(10) cycles reduction at PEF time 547 mu s and pulsed electric strength 40 kV/cm, respectively. The inactivation of E. coli, S. aureus, and SLOX as a function PEF time followed Weibull distribution. This study demonstrated that PEF could inactivate efficiently E. coli, S. aureus, and SLOX without affecting the quality characteristics of soymilk. Thus, this technique could be an advantageous alternative to heat treatment for pasteurization of soymilk.