Combined effects of comminution and gamma irradiation on the physicochemical, techno-functional, and antioxidant properties of defatted rice bran

• Comminution and gamma irradiation reduced DRB to smaller particle sizes. • Structural and physicochemical properties of DRB were modified by comminution and irradiation. • Techno-functional and antioxidant properties of DRB were enhanced. • Combined treatment improved the total phenolic content and antioxidant activity of DRB. • These changes support targeted use of DRB in functional food applications. Defatted rice bran (DRB) is a nutrient-rich byproduct of the rice bran oil industry, yet its utilization in food systems is often limited by its coarse texture and suboptimal functional properties. It was hypothesized that the synergistic application of physical comminution and gamma irradiation could induce structural modifications, thereby enhancing its techno-functional properties and bioactive accessibility. The combined effects of three mesh sizes (50, 100, and 140 mesh) and gamma irradiation doses (0, 5, and 10 kGy) were investigated. SEM and particle size analysis confirmed that these treatments effectively reduced particle size and altered surface morphology. XRD analysis indicated that gamma irradiation tended to reduce the overall crystallinity (%) of DRB across all sizes. Regarding color, comminution increased the total color difference (ΔE) at the same radiation dose, whereas gamma irradiation conversely reduced ΔE at finer mesh sizes. These structural changes markedly influenced techno-functional attributes; specifically, the combination of finer grinding and irradiation decreased water-holding, swelling, and oil-binding capacities, while significantly increasing the water solubility index. Furthermore, the treatments significantly enhanced total phenolic content and antioxidant activity. This study demonstrates a unique synergistic effect on the microstructural-functional relationship of DRB, highlighting its potential as a versatile functional ingredient for upcycling agricultural byproducts into high-value food applications.