Effect of rice protein incorporation on the rheological, structural, and iron bioaccessibility properties of rice flour-based composite hydrogels

Hydrogels were formulated using rice flour (RF) and rice protein (RP) at varying concentrations (5-25%) to develop a functional, plant-based delivery system for iron fortification. Increasing RP content delayed starch gelatinization and decreased peak viscosity from 20,345 mPa·s (F100P0) to 5887 mPa·s (F75P25), indicating modified pasting behavior and reduced starch retrogradation. Textural analysis revealed a reduction in hardness from 6.05 N to 0.18 N with increasing RP, while cohesiveness decreased from 0.35 to 0.09. SEM analysis showed RP-rich gels exhibited compact, honeycomb-like porous networks. FTIR confirmed hydrogen bonding between starch and protein, while XRD analysis showed a V-type structure, and crystallinity decreased from 24.4% to 11.17% as RP increased. In-vitro studies revealed that starch hydrolysis decreased from 93% to 82%, while protein digestibility increased from 74.7% to 92.8%. Iron bioaccessibility increased from 52.3% to 78.6%, suggesting RF-RP hydrogels as promising carriers for micronutrient delivery.