The aim of this research was to investigate the efficacy of the duty ratio and applied voltage in the inactivation of pathogens in soybean curd by pulsed ohmic heating (POH). The heating rate of soybean curd increased rapidly as the applied voltage increased, although the duty ratio did not affect the temperature profile. We supported this result by verifying that electrical conductivity increased with the applied voltage. Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes in soybean curd were significantly (P < 0.05) inactivated by more than 1 log unit at 80 V_rms (root mean square voltage). To elucidate the mechanism underlying these results, the membrane potential of the pathogens was examined using DiBAC₄(3) [bis-(1,3-dibutylbarbituric acid)trimethine oxonol] on the basis of a previous study showing that the electric field generated by ohmic heating affected the membrane potential of cells. The values of DiBAC₄(3) accumulation increased under increasing applied voltage, and they were significantly (P < 0.05) higher at 80 V_rms, while the duty ratio had no effect. In addition, morphological analysis via transmission electron microscopy showed that electroporation and expulsion of intracellular materials were predominant at 80 V_rms. Moreover, electrode corrosion was overcome by the POH technique, and the textural and color properties of soybean curd were preserved. These results substantiate the idea that the applied voltage has a profound effect on the microbial inactivation of POH as a consequence of not only the thermal effect, but also the nonthermal effect, of the electric field, whereas the duty ratio does not have such an effect.

中文翻译：

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脉冲欧姆加热下豆腐中病原体的灭活动力学和膜电位取决于所施加的电压和占空比。


本研究的目的是研究占空比和施加电压在脉冲欧姆加热（POH）灭活豆腐中病原体的效果。尽管占空比不影响温度分布，但随着施加电压的增加，豆腐的加热速率迅速增加。我们通过验证电导率随着施加的电压而增加来支持这一结果。在 80 V _rms （均方根电压）下，豆腐中的大肠杆菌O157:H7、肠沙门氏菌鼠伤寒血清型和单核细胞增生李斯特氏菌显着灭活 ( P < 0.05) 超过 1 个对数单位。为了阐明这些结果背后的机制，根据先前的研究，使用 DiBAC ₄ (3) [双-(1,3-二丁基巴比妥酸)三甲川氧杂菁]检查了病原体的膜电位，该研究表明，由欧姆加热影响细胞膜电位。随着外加电压的增加，DiBAC ₄ (3) 累积值增加，并且在80 V _rms时显着更高( P < 0.05)，而占空比没有影响。此外，通过透射电子显微镜进行的形态分析表明，电穿孔和细胞内物质的排出在 80 V _rms下占主导地位。此外，POH技术克服了电极腐蚀，并保留了豆腐的质地和颜色特性。 这些结果证实了这样的观点：所施加的电压对 POH 的微生物灭活具有深远的影响，这不仅是由于电场的热效应，而且还因为电场的非热效应，而占空比则没有这种影响。 。