高压脉冲电参数对苹果介电特性影响试验研究

摘要

Vacuum freeze drying fruit and vegetable processing can enhance fruit and vegetable cell permeability and reduce energy consumption of freeze by high-voltage pulsed electric field processing technology. Therefore, fruits and vegetables show on the dielectric properties under the action of electric field, research fruits and vegetables has a certain significance in on-line monitoring lyophilizing about changing of water and freeze-dried process optimization, etc. Based on apple's material, high-voltage pulsed electric field for apple is pretreated. In the electric field frequency range is 102~106 Hz, determining the electrical parameters of apple, such as equivalent capacitance and equivalent impedance. Using the MATLAB software to analyze the test data, the influence of the pulse voltage and frequency on dielectric properties is understood. The results show that the equivalent capacitance and equivalent impedance of apple is decrease with the pulse voltage, the pulse frequency increase. And when the electric field frequency is the 0~500 Hz, apple's equivalent impedance higher then the equivalent capacitance of the sensitivity of the high-voltage pulsed electric field pretreatment test. The electric field frequency is 500 Hz, the electric field voltage is 1 V, apple's equivalent capacitance, impedance and water content rate have significant correlation. Using the dielectric properties detect fruit and vegetable moisture is viable.%　　真空冷冻干燥果蔬加工中采用高压脉冲电场处理技术能够增强果蔬细胞通透性而降低冻干能耗，因此基于果蔬在外电场作用下表现出的介电特性，在研究果蔬在线监测冻干水分变化、冻干工艺优化等方面有一定意义。以苹果为试材，对苹果进行高压脉冲电场预处理，在频率为102~106 Hz内测定苹果的等效电容、等效阻抗等电学参数，运用MATLAB软件对试验数据进行分析解脉冲电压、频率对介电特性的影响。结果表明，苹果的等效电容、等效阻抗均随脉冲电压、脉冲频率的增大而减小，且当测试频率在0~500 Hz时，苹果的等效阻抗对高压脉冲电场预处理试验的敏感性高于等效电容。测试频率为500 Hz，测试电压为1 V时，苹果的等效电容、阻抗与含水率均呈现显著相关关系，利用介电特性进行果蔬含水率检测可行。