Physicochemical properties of rice bran after ball milling

Abstract

The particle size of rice bran is a critical characteristic for the processing and eating quality of rice bran food. After hammer milling and ball milling, the physicochemical properties of rice bran with different particle size (203.33, 101.33, 71.10, 41.80, and 18.90 µm) were investigated, including hydration properties, antioxidant properties, nutritional properties, and microstructure features. Rice bran with small particle size (D50 18.90 µm) exhibited higher water solubility index, antioxidant activities, and γ-oryzanol and γ-aminobutyric acid content, and the swelling capacity was 1.37 times that of large size (D50 203.33 µm). The insoluble dietary fiber of rice bran converted into soluble dietary fiber after ball milling. Mercury intrusion, scanning electron microscope, Fourier transform infrared spectrometry, and X-ray diffraction showed that as the particle size decreasing, there was an increase in pore area, decrease in porosity, and exposure of hydrophilic groups, breakage of cellulose structure. Practical applications The particle size of rice bran was reduced to superfine powder with D50 18.9 µm by ball milling. The hydration properties of rice bran were significantly improved after ball milling. The superfine rice bran powder exhibited high antioxidant activities and nutritional properties.