Minimally-destructive evaluation of durian maturity based on electrical impedance measurement

Electrical impedance spectroscopy was investigated to model the dry matter content of durian using partial least squares regression. Measurements of the impedance were taken on the stem and the rind of durian samples at various stages of maturity based on the number of days after anthesis. Plots of the relationship between resistance and reactance, and the change in impedance and capacitance with respect to frequency in a range of 1-200 kHz were explored to determine the optimal frequencies associated with variation in the number of days after anthesis. The impedance parameters at frequencies of 1, 41 and 200 kHz were employed to model the dry matter content of the pulp. The reactance of the cross section of the stem and the capacitance of the rind were found to predominantly contribute to the prediction of the dry matter content. Selected impedance parameters using a stepwise regression could be used to classify durian samples into an immature class and mature class with less accuracy of 83.3%. (c) 2012 Elsevier Ltd. All rights reserved.