Analysis of dielectric properties of rice during microwave drying process

Background and Objectives

In the process of microwave drying rice, the dielectric property determines the ability of rice to absorb microwave, and the change of dielectric constant and dielectric loss factor has a great influence on the microwave drying of rice. Therefore, it is necessary to predict the change of the dielectric constant and dielectric loss factor of rice.

Findings

This study investigated the intermediate electrical characteristics of rice during microwave drying. It explored their relationship with temperature, water content, and microwave frequency. A mathematical model was developed at frequencies of 2.45 GHz and 500–3000 MHz to predict temperature, water content, dielectric constant, and dielectric loss factor. Additionally, the model predicted the microwave penetration depth based on the dielectric constant and dielectric loss factor.

Conclusions

In microwave drying, rice dielectric constant and loss factor increase with temperature and moisture content. However, they follow a trend of initially decreasing and then increasing with frequency. By leveraging these predictable properties, we calculated the microwave penetration depth during drying, providing a new direction for future microwave technology in rice processing.

Significance and Novelty

This study unveiled variations in the dielectric constant and loss factor during rice microwave drying. Employing the mathematical model based on these factors can enhance the efficiency of rice microwave drying by judiciously elevating the drying temperature.