Study on the relationship between lutein bioaccessibility and in vitro lipid digestion of nanostructured lipid carriers with different interface structures

This study compounded natural macromolecules whey protein isolate with small molecule surfactant Tween 80 to construct lutein nanostructured lipid carriers (Lutein-NLCs) with three different interface structures, including single-interface (S-Lutein-NLCs), composite-interface (C-Lutein-NLCs) and double-layer interface (D-LuteinNLCs) Lutein-NLCs. The kinetics process of lipid hydrolysis, mixed micelles formation of MAGs, FFAs and lutein as well as its bioaccessibility were quantified. The results showed that S-Lutein-NLCs and C-Lutein-NLCs presented a stronger ability to resist bile salt displacement compared to D-Lutein-NLCs. C-Lutein-NLCs and D-LuteinNLCs exhibited a lower speed of lipid hydrolysis in comparison with S-Lutein-NLCs. This induced a slower, as well as a lower incorporation degree of lutein into mixed micelles. In this regard, S-Lutein-NLCs showed a significantly higher Cf value of lutein bioaccessibility than D-Lutein-NLCs and C-Lutein-NLCs. The release of MAGs and FFAs significantly affected the micellization of lutein and its bioaccessibility. In terms of Cf value, there were significant positive correlations between the hydrolysis of TAGs and lutein release, lutein release and its bioaccessibility, as well as MAGs and FFAs micellization and lutein bioaccessibility. Nonetheless, D-LuteinNLCs and C-Lutein-NLCs exhibited a better sustained-release effect compared to S-Lutein-NLCs. Furthermore, CLutein-NLCs presented a stronger inhibitory effect on the degradation of lutein, with the lutein retention rate of 50.65%, which was 12.06 times that of the free lutein. This study will provide new ideas for the design and application of nanostructured lipid carriers.