Enhancing Rice Bran Soluble Dietary Fiber Yield Through Sequential Ultrasound–Xylanase Treatment

The main aim of this study was to enhance the content of soluble dietary fiber (SDF) derived from rice bran (RB) through various treatments, including physical methods (ultrasound and alternating magnetic field (AMF)) and enzymatic approaches (cellulase and xylanase), applied individually or in combination. The results revealed that AMF treatment was the most effective single modification technique for increasing SDF yield, followed by treatments with xylanase, cellulase, and ultrasound. Notably, among the combined approaches, the sequential ultrasound–xylanase treatment (U-X) demonstrated the highest potential for enhancing SDF yield. Further optimization experiments revealed that under the conditions of a xylanase addition of 4.3 mg/g sample, a material-to-liquid ratio of 50 mL/g, and an ultrasonic power of 72 W, the yield of U-X-SDF significantly increased from 1.03% to 18.4%. Compared to unmodified samples, the modified SDF groups exhibited marked enhancements in water holding capacity (42.5–86.4%) and water solubility (21.0–30.6%), while the unmodified SDF displayed superior oil holding capacity than the modified groups. In summary, the sequential ultrasound–xylanase treatment not only improves the SDF yield but also enhances the functional properties of RB-derived SDF, positioning it as a valuable health-promoting food additive with potential benefits for both laboratory and industrial food applications. The optimized treatment process can contribute to the development of new functional food ingredients from RB, thereby promoting health and wellness in consumers.