Effect of particle size fractionation and solvent-assisted de-oiling on the physico-chemical properties and protein solubility of rice bran

This study investigates the particle size-based fractionation of rice bran (RB) and its impact on various physicochemical and functional properties. RB was fractionated using A.S.T.M. sieves into three primary fractions: RBF I (≥0.42 mm), RBF II (≥0.25 mm), and RBF III (≥0.18 mm). Particle size distribution (PSD) analysis revealed a progressive reduction in mean particle size from 261.37 μm (RBF I) to 159.3 μm (RBF III), with a corresponding increase in specific surface area. Proximate analysis indicated minimal variations in moisture, protein, fat, and ash content among fractions. Color analysis showed that finer fractions exhibited higher L^* values, indicating increased lightness. Flow property assessments revealed decreasing bulk and tapped densities with decreasing particle size, leading to reduced flowability. Hydration properties remained relatively stable, with water absorption capacity ranging from 3.6 to 3.72 gg^-1 and water activity values ensuring microbial stability. Solvent-aided de-oiling trials demonstrated that hexane was the most effective solvent, yielding the lowest residual oil content (1.26%) while preserving protein solubility. The findings highlight the potential of size-based RB fractionation for enhancing its industrial applicability in food, optimizing processing efficiency while maintaining nutritional integrity. In conclusion, RBF III (≥0.18 mm) emerges as the most promising fraction, with improved lightness, higher surface area, and effective oil removal, making it the best choice for functional and industrial applications.