A novel phytosterols delivery system based on sodium caseinate-pectin soluble complexes: Improving stability and bioaccessibility

In this study, sodium caseinate (NaCas)/pectin-based phytosterols (NCP-PSs) nanoparticles were successfully prepared by emulsification evaporation and complex coacervation techniques to improve the bioaccessibility of phytosterols. The optimal mass ratio of NaCas to pectin in NCP-PSs nanoparticles was 2:1. Under these conditions, phytosterols were successfully loaded in NCP-PSs nanoparticles with high encapsulation efficiency (91%) and loading capacity (21%). The nanoparticle size was about 240 nm and the polydispersity index was less than 0.3. Fourier transform infrared spectroscopy indicated the existence of electrostatic interaction between NaCas and pectin and the formation of hydrogen bonds between phytosterols and NaCas. X-ray diffraction analyses proved that the phytosterols changed from an ordered crystalline state to a disordered amorphous state by nano-encapsulation. Circular dichroism demonstrated that the encapsulation of phytosterols induced conformational changes of NaCas. Fluorescence spectroscopy revealed the occurrence of hydrophobic interactions between phytosterols and NaCas. The results of storage experiment illustrated that NCP-PSs nanoparticles were stable against dissociation and thus can provide excellent encapsulation and protection for phytosterols. The bioaccessibility of phytosterols encapsulated in NCP-PSs nanoparticles was increased by at least 43.8% compared to free phytosterols and phytosterols encapsulated in NaCas-based nanoparticles, indicating that the presence of pectin improves the bioaccessibility of phytosterols. Consequently, this study provided a novel phytosterols delivery system based on NaCas-pectin soluble complexes, which has a broad prospect in the processing of food, nutrition, and pharmaceuticals.