Fabrication and characterization of soy isoflavones-oat β-glucan complexes: Improvement on the antioxidant activity and release rate

The interaction between polyphenols and polysaccharides has the potential to enhance the stability and antioxidant activity of natural polyphenols. This study investigated the complexation between soy isoflavones (SI) and oat β-glucan (OBG) under different conditions (ratio, pH, and temperature). When the ratio was 1:1, pH was 5 and 40 °C, the binding rate and turbidity were 65.1% and 0.461. Additionally, in comparison to SI alone, it was observed that a higher binding rate correlated with an increase in phenolic hydroxyl groups present, which subsequently enhanced the ABTS•+ scavenging rate. After digestion, these complexes dissociated to expose additional active sites, resulting in superior antioxidant capacity compared to SI alone, and more SI was released (21.4%). Transmission electron microscopy (TEM) confirmed successful preparation of spherical complexes. Fourier-transform infrared (FT-IR) spectroscopy and nuclear magnetic resonance (NMR) analyses revealed that hydrogen bonding served as the primary binding force between SI and OBG. Furthermore, X-ray diffraction (XRD) and differential scanning calorimetry (DSC) demonstrated that SI was incorporated into the network structure of OBG by inclusion. This study elucidates both the interaction mechanism between SI and OBG as well as their enhancement of antioxidant capacity, providing valuable theoretical insights for designing dietary fiber and polyphenol systems. • The complex (SI-OBG) was fabricated used oat β-glucan and soybean isoflavone as raw materials. • The preparation conditions of SI-OBG were determined as a ratio of 1:1, pH = 5, and 40 °C. • The ABTS•+clearance rate of the SI-OBG was significantly enhanced. • The release rate of SI from SI-OBG (21.36%) increased after in vitro digestion compared with that of SI. • Hydrogen bonding acted as the main binding force between SI and OBG.