Improvement in Physicochemical and Functional Properties of Insoluble Dietary Fiber from Rice Bran Treated with Different Processing Methods

Rice bran represents an exceptional natural source of dietary fiber (DF), and its physicochemical properties and therapeutic potential are closely associated with its origin and processing methods. Herein, rice bran was subjected to extrusion, fermentation, and a combined treatment of fermentation and extrusion to explore the alternations in the structural, physicochemical, and functional properties of the resulting insoluble dietary fiber (IDF). All treatments induced substantial microstructural alterations in IDF, producing fiber matrices with enhanced porosity and looser architectures. The employed processing treatments significantly enhanced the functional properties of rice bran IDF over the unprocessed sample, with 1.37- to 1.78-fold increases in oil-holding capacity, 1.31- to 1.48-fold increases in cholesterol-adsorption capacity, 2.89- to 5.90-fold increases in α-amylase-inhibitory activity, and 2.41- to 3.70-fold increases in glucose-adsorption capacity. Among them, extrusion proved more effective than fermentation in enhancing the water-holding capacity, sodium cholate binding, and cholesterol-adsorption capacity of rice bran IDF. However, fermented rice bran-derived IDF exhibited the optimum α-amylase-inhibitory and glucose-absorption capacities among all employed IDF samples. These findings provide valuable insights for the development of rice bran-based functional foods with enhanced health benefits.