Combination of Thermosonication and Pulsed Electric Fields Treatments for Controlling Saccharomyces cerevisiae in Chinese Rice Wine

The objective of this study was to investigate the combined effect of thermosonication (TS) and pulsed electric fields (PEF) against Saccharomyces cerevisiae in Chinese rice wine. The effectiveness of standalone TS treatment (35 °C, 750  W, 120 min) on the inactivation of S. cerevisiae was insignificant (0.76 log CFU/mL). However, 2.88 log CFU/mL of S. cerevisiae were inactivated when the standalone PEF treatment with moderate conditions (35 °C, 12 kV/cm, 120 μs) was applied. The combination of TS and PEF had an additive effect on the inactivation of S. cerevisiae, and the sequence applied (TS-PEF or PEF-TS) markedly influenced the inactivation results (P < 0.05). In particular, the microbial inactivation by TS-PEF (3.72 log CFU/mL) was higher than that by PEF-TS (3.48 log CFU/mL); this result indicates that PEF were able to restrain the effect of TS. On the other hand, TEM micrographs of S. cerevisiae after the different treatments showed that the combined techniques resulted in more severe disruptions on cells. Higher cytoplasmic shrinkage and more intracellular material leakage were observed from the TEM observations of the cells treated by TS-PEF. These results may serve as a reference of the potential application of the combined treatment TS-PEF for microbial inactivation in Chinese rice wine.