Modeling of yeast inactivation of PEF-treated Chinese rice wine: Effects of electric field intensity, treatment time and initial temperature

Abstract

The application of pulsed electric field (PEF) technology as an alternative method of spoilage microbiological control for Chinese rice wine was investigated. PEF was applied at the initial temperature of 25–35°C, the electric field strength of 12–21kV/cm, with respective treatment time of 30–180μs to evaluate the efficiency of this technology on the inactivation of spoilage yeast Saccharomyces cerevisiae commonly associated with rice wine. The results from atomic force microscope imaging of yeast cells indicated that PEF treatment induced the destruction of cell membrane structures, which supported by the decrease of yeast number, the blurring of images, and the flattened yeast border. The highest inactivation values, corresponding to approximately 5.5-log cycles, were obtained at 21kV/cm and 180μs with the initial treatment temperatures of 30 and 35°C, respectively. Based on calculations by both log-linear and Weibull models, the decimal reduction times (5-D values) over the range of treatment conditions were 336.53–1804.1μs and 150.17–1127.6μs, respectively. Then the 5-D values were fitted as a function of electric field strength and initial treatment temperature, with R2 of 0.986 and 0.963 for log-linear and Weibull model, respectively. The model validation results showed that the 5-D values calculated from Weibull model (Af=1.169 and Bf=0.996) provided more accuracy than those from log-linear model (Af=1.773 and Bf=1.773), suggesting that the Weibull model was more suitable for calculating the survival ratio of PEF-treated spoilage microorganisms in Chinese rice wine. Finally, the effects of PEF treatment on physicochemical properties (including °Brix, pH, conductivity and color) of rice wine exactly after treatment and during storage at room temperature (22°C) were also investigated. The results indicated that PEF was able to inactivate (to some degree) the yeast in rice wine with minor variations in the physicochemical parameters and affect the quality indices of rice wine positively.