Preparation and characterization of quercetin-loaded nanoparticles based on soy protein isolate-oat β-glucan extrudates: Interaction, structure, stability, and in vitro release properties

Soy protein isolate (SPI)-oat β-glucan (OG) conjugates produced by extrusion were used to prepare nanoparticle carriers for improving quercetin stability. The 70–130 °C SPI-OG extrudate nanoparticles exhibited higher encapsulation efficiency (EE, 75.63–80.30 %) and loading capacity (LC, 46.22–50.83 %), especially 90°C (EE and LC were 80.30 % and 50.83 %, respectively) and 110 °C (EE and LC were 79.84 % and 49.26 %, respectively) SPI-OG extrudate nanoparticles. The average particle size of quercetin-loaded SPI-OG extrudate nanoparticles ranged from 185.77 nm to 244.07 nm. SPI-OG extrudates around quercetin were tightly bound to it through hydrogen bonding and hydrophobic interactions, resulting in the structure of quercetin to change from crystalline state to amorphous state. Stability results of quercetin indicated that SPI-OG extrudate nanoparticles could more effectively protect the antioxidant activity of quercetin and improve its storage stability (quercetin retention of 31.89–39.82 % after 21 days). Meanwhile, SPI-OG extrudate nanoparticles mainly continuously released quercetin during the simulated intestinal digestion (cumulative release rate was 18.99–21.10 % in intestinal stage). These results indicated that SPI-OG extrudate nanoparticles could effectively encapsulate quercetin and prolong its biological activity, thus could be applied in nutritional supplements and functional foods.