电极间隙对脉冲电场处理器杀菌效果的影响

Effect of Electrode Gap on the Sterilization Effect of Pulsed Electric Field Processor

脉冲电场是新型非热杀菌技术,杀菌效率高、有效保留液体食品的营养成分,具有广阔的应用前景。电极间隙作为脉冲电场杀菌处理器的关键指标,决定处理器的电场分布和杀菌效果。为了获得最佳间隙参数,提升杀菌效果,为此设计了共场型脉冲电场处理器,电极间距分别为3、5和7 mm,针对固定电导率(等效鲜榨柚子汁电导率)的2种典型细菌(金黄色葡萄球菌和大肠杆菌)菌悬液,研究了脉冲电场的杀菌效果。研究发现,3 mm电极间距所能施加最大电压为18 kV,5、7 mm的可达30 kV;处理时间为120 s时,3种间隙的杀菌效率均可达99.99%。因此,综合考虑电源性能、设备能耗和处理能力,首选3 mm电极间距为处理器的应用参数。评估外施电压幅值对杀菌效果的影响,发现细菌存活量的下降趋势可根据其下降速率分为“慢-快-慢”3个阶段。结合菌悬液上清液蛋白质含量的上升趋势,充分说明了电穿孔应为脉冲电场的主要杀菌机制。

Pulsed electric field(PEF)is a new non-thermal sterilization technology that has high sterilization efficiency and effectively preserves the nutritional components of liquid food,showing application prospects.As one of the key indexes of PEF sterilization processor,electrode gap dominates the distribution of electric field and directly affects the sterilization effect.In order to optimize the optimal gap parameters and explore the sterilization effect,we designed PEF processors with different electrode gaps(3 mm,5 mm and 7 mm),and investigated the sterilization effect of PEF on two typical bacteria(staphylococcus aureus and escherichia coli)suspension with specified conductivity(equivalent fresh squeezed grapefruit juice conductivity).The study shows that the maximum voltage that can be applied to the 3 mm electrode gap is 18 kV,while 5 mm and 7 mm gaps can reach 30 kV.When the treatment time is 120 s,the sterilization efficiency of all three gaps can reach 99.99%.Therefore,after the performance of the power supply,energy consumption,and processing capacity are taken into consideration,the 3 mm processor is proposed as the preferred option for application.The influence of applied voltage amplitude on the sterilization effect was evaluated,and it was found that the bacteria content decreased with the increase of applied voltage in a“slow-fast-slow”three-stage process.Furthermore,the trend of change in protein content in the supernatant of bacterial suspension was analyzed,which was found to be in good agreement with the trend of sterilization effect change.Therefore,the results fully indicate that the main mechanism of PEF sterilization is the electroporation of bacterial cells.