脉冲电压作用下液体食品等效阻抗测量

Measurement of Liquid Food Equivalent Impedance Under Impulse Voltage

导电性液体食品异常击穿是脉冲电场灭菌技术中的技术瓶颈之一。为了深入研究液体异常击穿机理,需要准确的测量被处理液体的等效阻抗。提出利用方波脉冲对高导电性液体食品的等效阻抗进行测量,通过对三种不同的电压施加方案的比较,选取了一种对测量结果影响最小的脉冲电压施加方案。并对自来水、橙汁、自然脱气啤酒和牛奶的等效阻抗进行了测量。测量结果表明:等效电阻按自来水、橙汁、自然脱气啤酒和牛奶依次减小,而等效电容则依次增大;脉冲电压作用下的等效电阻测量结果普遍小于稳态电压下的测量结果且偏差较大,而脉冲电压作用下的等效电容测量结果则大于稳态电压下的测量结果且偏差更大,这一结果表明被测量液体食品在脉冲电压作用下的导电和极化情况有可能与稳态电压作用下的不同。对测量过程中存在的直流偏置现象进行了解释和实验验证,并对测量过程中出现的其它现象进行了解释。

Abnormal breakdown of conductivity liquid food is one of bottlenecks in pulsed electric field sterilization technology. The equivalent impedance should be calculated precisely in order to research the mechanism of abnormal breakdown deeply. We propose a square wave pulse method to measure the equivalent impedance of high conductivity liquid food in the treatment chamber. A pulsed voltage supply program with the least influence to the measuring results is chosen to perform the measurement after three pulse voltage supply programs are compared. Then tap water, orange juice, naturally degassing beer, and milk are measured. The measurement results show that the equivalent resistance decreases with tap water, orange juice, natural degassing beer, milk, and contrarily, and the equivalent capacitance increases with the same order. The measured value of the equivalent resistance under pulsed voltage is smaller than the value of the equivalent resistance under steady voltage, and the difference is relatively remarkable. The measured value of the equivalent capacitance under pulsed voltage is bigger than the value of the equivalent capacitance under steady voltage, and the difference is also relatively remarkable. The result implies that the electric conduction process and the electric polarization process may be different at the pulsed voltage and steady voltage. The DC bias phenomenon of pulse waveform during the measuring process are explained and verified by experiments, and the other phenomena during the measuring process are explained..