The regulation of sodium alginate on the stability of ovalbumin-pectin complexes for VD encapsulation and in vitro simulated gastrointestinal digestion study.

The ovalbumin (OVA)-pectin (PEC)-sodium alginate (SA)-Vitamin D (VD) complex nanoparticles were fabricated by antisolvent precipitation method, and the excellent encapsulation efficiency and loading capacity of VD were obtained by 96.6% and 2.8%, respectively. Compared with ternary OVA-PEC-VD complexes, the addition of SA with strong negative charge effectively regulated the OVA-PEC complexes and significantly improved the stability of OVA-PEC-SA-VD complex nanoparticles with preferable size as small as 126 nm. The storage stability was also investigated after low temperature storage for 31 d, and the particle size of quaternary complexes was increased only 40 nm. In vitro digestion results elucidated that the complex nanoparticles had good stability in the simulated gastric fluid, and almost completely released in the simulated intestinal fluid confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) experiments and scanning electron microscope (SEM) images. The release kinetics study clarified that it was close to Fick release. Fluorescence and Fourier transform infrared spectroscopy (FTIR) experiments showed that quaternary complex nanoparticles were mainly combined by electrostatic, hydrophobic and hydrogen bonding interactions. The novel quaternary protein-polysaccharide complexes have excellent stability and great sustained-release performance for VD, which may be helpful for the digestion and absorption of vitamin by human body, thus have potential applications in the food and drug industry.