Prediction of Moisture Content Changes of Kidney Beans during Drying

Abstract

Thin layer drying characteristics of two kinds of kidney beans ('Ohtebo' and 'Taishokintoki') were measured under several drying conditions (temperature and relative humidity). From the drying characteristic curves, it was confirmed that the drying characteristics of the sample beans were in the second falling rate period. The measured values of moisture content change for each measurement condition of each sample were fitted to five mathematical models ; the infinite plane sheet model, the infinite cylinder model, and the sphere model, which are the exact solutions for the diffusion equation, the exponential model and the Page equation, respectively. The measurement results agreed well with the results calculated from the sphere model for 'Ohtebo', and the infinite plane sheet model for 'Taishokintoki'. Therefore, these models could be used to estimate the moisture content changes ofeach sample. The values of the diffusion coefficient were determined from the drying rate constant for each sample. An Arrhenius-type equation was used to relate the diffusion coefficient of each sample to temperature.