Ethanol-assisted rice protein-curcumin complexes as a natural encapsulation system to improve solubility and stability of curcumin.

Curcumin, a bioactive polyphenol from turmeric, exhibits strong antioxidant potential but has poor solubility and stability in water. This study developed ethanol-assisted rice protein-curcumin (RP-Cur) complexes to enhance curcumin dispersibility and stability. Complexes prepared with different ethanol ratios were characterized by zeta potential, fluorescence, and FT-IR analyses. Increasing ethanol content decreased surface charge and ANS fluorescence, indicating strengthened hydrophobic interactions and hydrogen bonding between RP and curcumin. Encapsulation efficiency exceeded 90% at ≥ 30% ethanol. DPPH assays showed that antioxidant activity was retained in RP-Cur complexes, with the highest activity and curcumin retention observed at 40-50% ethanol. These results demonstrate that ethanol-assisted complexation effectively improved curcumin solubility and stability while maintaining its antioxidant capacity. RP therefore represents a promising, sustainable encapsulant for curcumin in functional food and nutraceutical applications.