Relationship between moisture content and electrical impedance of carrot slices during drying
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Department of Physics, Slovak University of Agriculture in Nitra, Tr. A Hlinku 2, SK-949 76 Nitra, Slovakia
Department of Physics and Control, Corvinus University of Budapest, Somlói út 14-16, H-1118 Budapest, Hungary
Department of Production Engineering, Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, SK-949 76 Nitra, Slovakia
Publication date: 2015-01-15
Int. Agrophys. 2015, 29(1): 61–66
Electrical properties of food materials can give information about the inner structure and physiological state of biological tissues. Generally, the process of drying of fruits and vegetables is followed by weight loss. The aim of this study was to measure the impedance spectra of carrot slices during drying and to correlate impedance parameters to moisture content in different drying periods. Cylindrical slices were cut out from the carrot root along the axis. The slices were dried in a Venticell 111 air oven at 50°C. The weight of the slices was measured with a DenverSI-603 electronic analytical and precision balance. The weigh­ing of the samples was performed every 30 min at the beginning of drying and every 60 min after the process. The moisture con­tent of the samples was calculated on wet basis. The magnitude and phase angle of electrical impedance of the slices were measured with HP 4284A and 4285A precision LCR meters in the frequency range from 30 Hz to 1 MHz and from 75 kHz to 30 MHz, respectively, at voltage 1 V. The impedance measurement was per-formed after weighting. The change in the magnitude of impedance during drying showed a good correlation with the change in the moisture content.