间歇式HPEF的高压脉冲电源及其杀菌实验

Research on Sterilization of Pulsed Generator in HPEF Fixed Chamber

高压脉冲电场非热处理应用到食品杀菌可代替传统的热处理方法灭活液体中的病菌,高强度电脉冲能迅速杀死细胞但并不破坏食品的自然风味如色泽和营养,为此研制了高功率脉冲电源,其输出最高电压15 kV,最大电流40 A。在详细介绍了高功率电力电子器件IGBT使用过程中的过流和过压保护等问题和在输出端串联无感小电阻来修正波形实现了输出波形更陡峭的良好效果后,进行了两种相对难杀的典型微生物(枯草芽孢杆菌和黑曲霉菌)在间歇式处理室中的杀菌实验。结果表明,脉冲电场强度为13 kV/cm、脉冲宽度为15μs时,连续作用200个脉冲后,黑曲霉菌灭菌率能达99.64%,1000个脉冲后,所有的黑曲霉菌都被杀死;枯草芽孢杆菌相对难灭,在13kV/cm、15μs作用下灭菌率仅达87.08%;应在提高电场强度的同时避免放电,这对下一步的连续式杀菌实验有技术指导作用。

Application of high pulsed electric field （HPEF） in nonthermal food processing is an alternative technology to tranditional thermal processing. The high-intensity electric pulses kill rapidly microbial contaminants but do not change the natural taste of foods such as the color and nutrition. This study focused on preparing the high-power pulsed supply with the peak impulse voltage 15 kV and impulse current to 40A. The paper describes the protection in use of the high-power electron devices IGBT （ Insolate Gate Bipolar Translator）, including current protection and over voltage protection. In order to make the waveform more pefect, a small non inductive resistance in series is chosen to shape the output pulse voltage wave in the chamber. In the end of the paper, our emphasis is on inactivation of Aspergillus Niger and Bacillus, which are hard to be killed in water. The effects of the sterilization of these two main microorganisms are introduced. Experiment describes that the water solution of aspergillus niger was treated with the HPEF fixed static chamber at electric field strength of 13 kV/cm for 15 μs. The inactivation was 99. 64% at 200 numbers of pulses, while the treatment number increase to 1000, all the microorganism can be killed. The Bacillus, which has been cultivated after 72 hours, is hard to kill. At the same electric field strength condition, the inactivation of bacillus can only be to 87. 08% at 1000 number of pulses. Both improvement of the electric field intensity and reduction of the discharging probability will be a practical guide to the development and apptication of HPEF in the field of food processing engineering.