Study On The Correlation Between Electrical Properties And Physiological Properties Of Postharvest Starkrimson

In this study,electrical properties of Starkrimson were studied by using a HIOKI 3532-50 LCR tester. Electrical parameters included mainly complex impedance Z, equivalent parallel resistance Rp, reactance X, parallel equivalent capacitance Cp, parallel equivalent inductance Lp, paiallel equivalent resistance Rs, equivalent series inductance Ls, coefficient of losses D and electric conductance G. The correlations between electrical properties and physiological properties of post -harvest starkrimson were studied systematically in order to find the characteristic frequency and sensitive electrical indexes and the possibility of nondestructive testing using electrical properties were discussed to reflect the postharvest fruits'quality. The effect of 1-Methylcyclopropene and mechanical damage treatment on sensitive electrical indexes and physiological changements of postharvest starkrimson were studied in order to verify the uniformity of relationship of the untreatment and treatment samples between electrical properties and physiological characteristics. The results will bring theoretical bases for nondestructive testing using electrical properties of fruit and establishment of fruit grade system.The results were as follows.(1) The variation of electrical parameters of starkrimson had some relationship with electric field frequency. Complex impedance Z, parallel equivalent resistance Rp,reactance X, parallel equivalent inductance Lp, parallel equivalent capacitance Cp, equivalent series inductance Ls and paiallel equivalent resistance Rs of starkrimson showed an decrease obviously with the increasing frequency, and electric conductance G increased continually, coefficient of losses D displayed the pattarn of waveform changes and parallel equivalent capacitance Cp firstly decreased and then increased.(2) The electrical parameters of starkrimson varied with the change of the storage period. With the fruit storage time, the complex impedance Z, parallel equivalent resistance Rp,reactance X, parallel equivalent inductance Lp and paiallel equivalent resistance Rs of starkrimson showed an obvious decrease,electric conductance G and parallel equivalent capacitance Cp increased continually, while the equivalent resistance Rs and loss coefficient D didn't show regularity with the storage time.(3) The 39.8 kHz may be the characteristic frequency of nondestructive testing using electrical properties of postharvest starkrimson. At the frequency of 39.8 kHz, the comprehensive correlation between 9 electrical properties and 5 physiological properties of postharvest starkrimson were the best.(4) At the 398 kHz, the significant correlations between flesh firmness and Z or Cp or Rs were found. A significant positive correlation between Z and flesh firmness was detected (R~2=0.9005, P=0.0011,y=14.815x-52.025). A significant negative correlation between Cp and flesh firmness was also found(R~2=0.8868, P=0.0015, y=-22.93x+14.713). The Z, Rs and Cp could indicate the variation of flesh firmness. There was a significant positive between Rp and fruit acidity(R~2=0.8216, P=0.012, y=0.8088x-0.0779). There was a negative between Cp and fruit acidity (R~2=0.8234, y=-1.2623x+4.7021). Both Rp and Cp could indicate the variation of fruit acidity. There was a significant positive correlation between the soluble solids and Rp(R~2=0.9236, P=0.002, y=1.7556x+4.3952). The Rp could indicate the variation of soluble solids. There was a significant negative correlation between Z and ethylene release rate(R~2=0.9597,P=0.008, y=-0.8052x+3.4811),while there was a negative correlation between the ethylene release rateand Cp(R~2=0.8198, y=-1.3521x+0.7989)There were negative correlations between respiratory rate and Z( R~2=0.8304, y=-48.486x+207.43) or Cp (R~2=0.8481, y=48.483x-3.1735).(5) The correlations between electrical properties and physiological properties of postharvest starkrimson were analyzed under characteristic frequency. The Z, Cp and Rp may be as the sensitive electrical indexes to reflect the fruit ripeness of starkrimson in the nondestructive testing.