Complexation with whey protein fibrils and chitosan: A potential vehicle for curcumin with improved aqueous dispersion stability and enhanced antioxidant activity

Whey protein fibrils (WPF) formed at 6, 12, 18, and 24 h (80 °C, pH 2) and chitosan were utilized as vehicles to enhance curcumin dispersion stability at pH 3.5. Their antioxidant activity and release behavior in vitro were investigated. Compared with whey protein isolates (WPI), WPF possessed higher surface hydrophobicity and ζ-potential without reducing solubility. The solubility of curcumin was improved to 297.8 ± 3.3 μg/mL (400 μg/mL added) via complexation with chitosan and WPF-18 (WPF formed at 18 h). The hydrophobic groups of fibrils, rather than those exposed due to the hydrolyzed peptides, accounted for major binding sites of curcumin. Chitosan and fibrils combined with curcumin formed a bicontinuous polymer through electrostatic interaction and increased the repulsive force between fibrils, resulting in a delivery system with increased stability. Compared with curcumin alone, the complexes showed significantly improved antioxidant activity (DPPH radical scavenging activity and reducing power). Moreover, the delivery systems further provided opportunities for curcumin to release in the intestine. This potential vehicle may contribute further to introduce curcumin into fat-free acidic functional beverages.