Abstract: A mathematical model for water content of small red beans with respect to relative dielectric loss factor, bulk density and temperature was set up and validated under a signal frequency of 500 kHz. The effects of measurement signal frequency (1 kHz－1 MHz), bulk density (747－851 kg/m3) and temperature (5－40 ℃) on relative dielectric loss factor were studied, and the mechanism underlying the change in relative dielectric loss factor was analyzed in theory. The results indicated that dielectric loss factor of small red beans revealed a decreasing trend with increasing signal frequency in the range of 1 kHz－1 MHz, but presented an opposite trend as the water content, bulk density and temperature increased. A quadratic model characterizing the relationship of water content with relative dielectric loss factor, bulk density and temperature was established with a determination coefficient of 0.9882.

Key words: small red bean, dielectric loss factor, water content, temperature, frequency, bulk density