Encapsulation of quercetin in biopolymer-coated zein nanoparticles: Formation, stability, antioxidant capacity, and bioaccessibility

Composite nanoparticles were fabricated by forming a caseinate/kappa-carrageenan coating around zein nanoparticles. Quercetin-loaded composite nanoparticles (d < 150 nm) were successfully prepared at a particle yield of 95.2%, nutraceutical loading capacity of 5.6%, and nutraceutical loading efficiency of 75.7%. The quercetin was present in an amorphous state inside the composite nanoparticles as determined using X-ray diffraction. The quercetin-loaded nanoparticle dispersion was resistant to aggregation when subjected to pH changes (pH 2.0 to 8.0), heating (90 °C for 120 min), CaCl2 addition (10 mM), and NaCl addition (2.0 M). The quercetin was mainly released from the composite nanoparticles in the intestinal stage of a simulated human gut. Quercetin bioaccessibility was enhanced after being encapsulated within the composite nanoparticles, which resulted in higher in vitro antioxidant activities (p < 0.05) and intracellular reactive oxygen species (ROS) (p < 0.01). Overall, the results of this study indicate that composite nanoparticles are effective at encapsulating, retaining, and delivering quercetin, and might therefore be utilized in dietary supplements, functional foods, and pharmaceutical products.