Effects of soaking temperature and ultrasonic power on the cooking time and physical properties of brown rice

The effect of ultrasonic soaking assisted microwave drying on the optimum cooking time and physicochemical properties of brown rice were investigated. After the ultrasonic soaking, the optimum cooking time of brown rice was significantly reduced, and the physical properties improved. The rice bran treated with high-temperature soaking and high-power ultrasound showed a porous structure with dense striped gaps. Accordingly, faster heat and mass transfer brought about the acceleration of drying rate and the reduction of drying time. The pretreatment and microwave drying reduced the gelatinization enthalpy (Delta H), which was beneficial to enhance the degree of gelatinization of starch. Microwave drying obviously increase the breakdown viscosity of brown rice flour, bringing about better tasting qualities. The content of free fatty acids, color parameters, and crystalline structure remained stable after pretreatment and microwave drying. Novelty impact statement Appropriate high-power ultrasound at the soaking temperature of 60 degrees C assisted microwave drying significantly altered the structure of brown rice bran, reduced the optimum cooking time, and improved the physical properties of brown rice. Ultimately, our research proved that soaking and ultrasound-assisted microwave was a promising way to produce instant brown rice with high quality.