Fate of lutein-containing zein nanoparticles following simulated gastric and intestinal digestion

Abstract

Zein nanoparticles (ZNPs) were prepared to encapsulate lutein via solvent-induced nanoprecipitation, and the stability of the zein nanoparticles with encapsulated lutein (ZLNPs) was determined following in vitro gastric and intestinal simulation. Stability was assessed by dynamic light scattering, gel electrophoresis, tendency towards sedimentation, and both atomic force and light microscopy. ZNPs possessed a hydrodynamic radius of ∼75 nm, which was not altered with incorporation of lutein. Gastric digestion conditions induced significant aggregation and sedimentation of ZLNPs, which were not fully digested by gastric enzymes and were found adhered to lipid droplets in light micrographs. Aggregation was decreased and digestion was promoted during gastric digestion if salt was omitted, indicating that a high ion concentration increased ZLNP aggregation and limited enzymatic digestion. ZLNPs were redispersed in intestinal conditions and completely digested into peptides. In comparison to aqueous lutein dispersions, incorporation within ZNPs increased lutein's digestive stability by ∼58% but reduced its micellarization efficiency by ∼42%. These findings indicated that ZNPs provided a degree of physical protection to encapsulated carotenoids in gastric conditions yet might partially interfere with certain pathways for carotenoid bioaccessibility.