Molecular-level insights into the interaction between soy protein isolate and fucoidan

Brown algae–derived fucoidan is a sulphated polysaccharide recognised for its wide-ranging biological activities and increasing significance in functional food development. While interactions with polysaccharides have been widely investigated, those with food proteins, such as soy protein isolate (SPI), remain underexplored, thereby hindering the rational design of stable and efficient biopolymer systems. Therefore, this study aims to investigate the intermolecular interactions between fucoidan and SPI using Fourier transform infrared (FTIR) spectroscopy and in silico molecular docking analysis. FTIR measurements revealed distinct shifts in the amide I and II regions of SPI and in the sulphate group peak of fucoidan, suggesting the involvement of hydrogen bonds and electrostatic attraction between the two biopolymers. Complementary in silico docking revealed favourable binding affinities for both 7S (Δ G bind , = 4.96 kcal mol −1 ) and 11S (Δ G bind = −3.98 kcal mol −1 ) globulins, with multiple interactions collectively stabilising the complex. Taken together, these findings offer molecular-level insights into SPI–fucoidan binding and highlight their potential applications in functional foods and biopolymer engineering.