Whey protein aggregates formed by non-toxic chemical cross-linking as novel carriers for curcumin delivery: Fabrication and characterization

Abstract

Whey protein isolate (WPI) was first treated with citric acid as a cross-linker to yield whey protein aggregates (WPA). Formation of aggregates through the covalent cross-linking was confirmed by SDS-PAGE. After that, with curcumin as a bioactive cargo, the potential application of WPA as carriers was investigated. WPA showed a remarkable higher loading capacity and efficiency for curcumin than non-treated WPI. The fluorescence spectroscopy revealed that curcumin could combine to WPA by hydrophobic interactions and quench the intrinsic fluorescence of WPA. The size, polydispersity index, viscosity, and consistency coefficient of WPA were significantly enhanced by adding of curcumin. The secondary structures of WPA were influenced by loading of curcumin as revealed by circular dichroism spectroscopy. X-ray diffraction and differential scanning calorimetry analysis revealed that the crystallinity of curcumin was decreased by loading into the WPA. In addition, the curcumin-loaded WPA had stronger antioxidant activity as measured by reducing power test than the free curcumin suggesting the additive effect between WPA and curcumin. The release studies showed that the release of curcumin from WPA in the gastric condition was relatively low, but increased in the simulated intestinal phase. Generally, the obtained whey protein aggregates are potential to become new curcumin delivery systems.