Abstract: This study evaluated the physicochemical and functional properties of water-soluble dietary fiber (SDF) prepared by ultrasonic-assisted cellulase hydrolysis of defatted rice bran. The SDF, with a high purity of (79.52 ± 0.07)%, had low protein and ash contents of (7.82 ± 0.13)% and (5.71 ± 0.11)%, respectively. The SDF had good physical and chemical properties; its water-holding capacity was (3.16 ± 0.15) g/g, oil-holding capacity (0.99 ± 0.08) g/g, swelling capacity (1.39 ± 0.12) mL/g, and water-binding capacity (4.18 ± 0.10) g/g. It was also found that the SDF had cation exchange capacity, and its solubility was positively proportional to temperature. Fourier transform infrared spectral analysis indicated the presence of some associated hydrogen bond in the SDF. Scanning electron microscopic analysis confirmed its high purity. Furthermore, the SDF exhibited strong antioxidant capacity in a concentration-dependent manner, which was determined to be 20.27% and 58.97% in the scavenging of 1,1-diphenyl-2-picrylhydrazyl and 2,2’-azinobis-(3-ethylbenzthiazoline-6- sulphonate) radicals at 10 mg/mL, respectively.

Key words: rice bran, water-soluble dietary fiber, physicochemical properties, antioxidant activity