Hatsuo Kojima

MEASUREMENT AND ANALYSIS OF MOISTURE CHANGES IN AGRICULTURAL PRODUCTS USING FFT NOISE IMPEDANCE SPECTROSCOPY

ABSTRACT Macroscopically, cellular foods including agricultural products are regarded as the electrical systems in which cell membranes isolate intracellular electrolytes from extracellular electrolytes. Moisture movement in the materials during drying causes the changes in moisture of the intracellular and extracellular electrolytes. Therefore, the moisture movements can be detected by an electrical measurement The authors measured the impedance of carrot roots during drying by a FFT (fast Fourier transform) noise impedance method at frequency of 40 Hz to 100 kHz. The equivalent circuit model agreed with the measured impedance. The parameters in the model were determined as the intracellular and extracellular resistances and membrane capacitance As a result, it was found that the increase in the extracellular resistance showed a good correlation with a decrease in moisture content between 200 and 400% d.b (dry basis) and that the membrane capacitance had the maximum near the second critical moisture cont...

Modelling of deep-bed grain drying

Abstract Generally grain is dried with a deep-bed after harvest. Its drying characteristics are too complex to investigate directly. Since a deep-bed is assumed to be composed of a series of thin-layers positioned perpendicular to drying air movement through a grain dryer, the drying characteristic of a thin-layer of grain needed to be investigated. The experiment of thin-layer drying was carried out with a laboratory dryer. First the drying process of wheat was divided into three drying periods with a view to improving the prediction accuracy of the drying model. Then, a two-term exponential model could be fitted to those drying periods. The two-term exponential model could predict the thin-layer drying process. Finally a state equation of the thin-layer drying process was developed from the differential heat and mass balances equations on the basis of the two-term exponential model. The step response to inlet drying air was calculated from the state equation. And the extention of the thin-layer model to the deep-bed drying process was discussed.