Soybean protein isolate-oxidized fucoidan nanocomplexes: Structural and interaction characterization, quercetin delivery potential evaluation

A novel nanocomplex was prepared using soybean protein isolate (SPI) and oxidized fucoidan (OFU) to explore the structural and interaction variations and evaluate its potential for quercetin delivery. The optimized SPI to OFU mass ratio of 10:1 (SFU3) resulted in a nanocomplex particle size of 198.1 nm and increased ζ-potential. The incorporation of OFU altered the structure of SPI with the decrease in α-helix and β-sheet, and the redshift and intensity drop in fluorescence spectra. X-ray photoelectron spectroscopy (XPS) confirmed the Schiff base reaction between the two, interacting through covalent imine bonds. Moreover, OFU improved the micromorphology, antioxidant capacity, and stability of Quercetin (Que) nanocomplexes, with SFU3 showing the highest encapsulation efficiency and loading amount (94.80 %, 16.96 μg/mg). The nanocomplexes achieved an effective controlled release of Que. in vitro simulated digestion. This study will provide important insights into the development of SPI-OFU as nutrient carriers.