基于介电参数同步监测苹果静压过程生理变化

The Simultaneous Monitoring of Physiological Change of Apple Based on Dielectric Parameters in Static Pressure

采用万能试验机对红富士苹果施加一定大小的静压力,在静压12 h的过程中,通过平行板电极法同步监测其介电参数,通过针状电极法同步监测其细胞外液体积分数。结果表明:随着静压力的延长,苹果相对介电常数和损耗因数增大。静压力一定时,随静压时间的延长,相对介电常数和损耗因数增大,细胞外液体积分数增大,且静压力越大细胞外液体积分数越大。细胞外液体积分数与相对介电参数高度相关(r>0.9),可通过介电参数的变化间接反映苹果生理变化。按照果实介电参数的变化,将其静压过程中的生理变化分成3个阶段:t≤0.5 h称为跃变阶段,此阶段介电参数平均变化率为28.19%/h;1 h≤t≤3 h称为渐变阶段,此阶段介电参数平均变化率为4.24%/h;4 h≤t≤12 h称为稳定阶段,此阶段介电参数平均变化率为0.67%/h,基本保持稳定。本研究为果品静压过程中理化品质和生理状态的同步监测研究提供新思路,也为采用介电特性法快速评价其受伤程度提供理论指导。

Dielectric parameters and volume percent of extracellular fluid of apples which were pressed under certain pressures 12 hours using universal testing machine were respectively monitored by parallel polar plate method and stainless steel electrode. The results were as follows: with static pressure increase, relative dielectric constant and loss factor were increase. In a certain static pressure, with time prolonging, relative dielectric constant and loss factor were increase, and volume percent of extracellular fluid also was increase and was bigger with pressure increase. There were high correlation between the volume percent of extracellular fluid and dielectric parameters(r>0.9), so the change of dielectric parameters could reflect the physiological change of apple. According to the changes of dielectric parameters during static pressure, the process of static pressure of apple was divided into three phases. They were rapid changes phase of dielectric parameter in t≤0.5 h in which average rate of change was 28.19%, slow changes phase in 1 h ≤t ≤3 h in which average rate of change was 4.24% and basically remained unchanged phase in 4 h≤t≤12 h in which average rate of change was 0.67%. The results show a new idea to simultaneously monitor physical and chemical quality and physiological state of fruits, and also provide a theoretical guidance for rapid evaluating the damage degree of fruit by the method of electrical characteristics.