Nondestructive Determination of Moisture Content in Dry Fruits by Impedance and Phase Angle Measurements


An electronic method to estimate the moisture content (MC) of dry fruits by measuring the impedance (Z) and phase angle (θ) of a cylindrical parallel-plate capacitor with dry fruit sample between the plates, using a CI meter (Chari’s Impedance meter) at 1 and 9 MHz is described. Capacitance C was derived from Z and θ, and using the C, θ, and Z values of a set of dried cherries, whose MC values were later determined by the vacuum hot air-oven method, a calibration equation was developed. Using this equation, and their measured C, θ, and Z values, the MC of a group of cherries, not used in the calibration, was predicted. The predicted values were compared with their air-oven values. Similar predictions were done using the same method on dried blueberries. The method worked well with a good R2 value, and showed a low standard error of prediction (SEP) in the measured MC range between 5% and 30% for cherries, and 9% and 22% for blueberries.

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Kandala, C. , Holser, R. , Sundaram, J. and Puppala, N. (2015) Nondestructive Determination of Moisture Content in Dry Fruits by Impedance and Phase Angle Measurements. Journal of Sensor Technology, 5, 73-80. doi: 10.4236/jst.2015.54008.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] Brothwell, D. and Brothwell, P. (1998) Food in Antiquity: A Survey of the Diet of Early People. John Hopkins University Press, Baltimore and London, 144-147.
[2] Hui, YH. (2006) Handbook of Fruits and Fruit Processing. Blackwell Publishing, Oxford, 81.
[3] AOAC (1990) Official Method of Analysis of the Association of Official Analytical Chemists. No. 934.06, AOAC, Arlington.
[4] Windham, W.R. (1989) Comparison between Liquid and Paste Karl Fischer Extraction for NIRS Water Calibrations. Journal of the Association of Official Analytical Chemists, 72, 255-258.
[5] Kandala, C.V.K. and Nelson, S.O. (1990) Measurement of Moisture Content in Single Kernels of Peanuts: A Nondestructive Electrical Method. Transactions of the ASAE, 33, 567-572.
[6] Kandala, C.V.K., Avula, R., Settaluri, V., Reddy, R.S. and Puppala, N. (2013) Sensing the Moisture Content of Dry Cherries—A Rapid and Nondestructive Method. Food and Nutrition Sciences, 4, 38-42.
[7] Kandala, C.V.K. and Sundaram, J. (2010) Nondestructive Measurement of Moisture Content Using a Parallel-Plate Capacitance Sensor for Grain and Nuts. IEEE Sensors Journal, 10, 1282-1287.
[8] Kandala, C.V.K., Butts, C.L. and Lamb, M.C. (2008) Moisture Content Determination for In-Shell Peanuts With a Low-Cost Impedance Analyzer and Capacitance Sensor. Transactions of the ASAE, 51, 1377-1381.
[9] Unscrambler, Version 9.7. CAMO Software Inc., Woodbridge.
[10] SAS Institute (2000) Statistical Analysis Software for Windows, Version 8.1, SAS Institute, Cary.

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