Formation, Structural Characteristics and Functional Properties of Quercetin–Oat β-Glucan Complex

Quercetin (QE), a flavonol-type polyphenol, and oat β-glucan (OβG), a soluble dietary fiber, are natural active ingredients with the potential to reduce the risk of diabetes. OβG slows starch digestion by modifying chyme viscosity, while QE inhibits digestive enzyme activity. This study aimed to explore the formation mechanism and structural characteristics of QE-OβG complexes, as well as their functional properties in terms of viscosity and amylase inhibitory activities. It was found that QE and OβG formed stable non-covalent complexes via hydrogen bonding and hydrophobic interactions. At a mass ratio of 0.6, the binding capacity was relatively high with a moderate aggregation degree, representing a balanced interaction state. Changes in turbidity and particle size indicated that different environmental factors (pH, temperature, ionic strength) exert differential effects on the aggregation behavior of the complex. In addition, the complex exhibited a unique fibrous-block morphology, enhanced thermal stability, improved starch system viscoelasticity, and stronger mixed-type reversible α-amylase inhibition (IC50 = 2.629 mg/mL). This study clarifies the interaction mechanism between QE and OβG, provides a reliable theoretical basis for the development of novel hypoglycemic foods, and offers new insights into multi-component regulation strategies for slow-digestion food design.