Unleashing the potential of ursolic acid: Improving the physicochemical stability, antioxidant capacity, and bioaccessibility of casein in goat milk

This study systematically investigated the physicochemical stability and functional properties of goat milk casein (CN) enhanced by jujube ursolic acid (UA) using spectroscopic techniques, molecular docking, and in vitro simulated digestion. The formation of the CN-UA complex was confirmed and found to be primarily driven by hydrogen bonding and hydrophobic interactions. These interactions induced significant conformational changes in CN, including a marked decrease in α-helix content and a corresponding increase in β-sheet content ( p < 0.05). Functionally, the complex formation resulted in a substantial enhancement of protein solubility and a notable increase in antioxidant activity. Furthermore, during in vitro digestion, the CN-UA complex improved gastric stability and promoted intestinal release and absorption. This study elucidates the underlying interaction mechanism and functional synergy between CN and UA, providing a critical strategy for designing innovative functional dairy products with improved antioxidant capacity and gastrointestinal stability. • UA improved the physicochemical stability of CN. • A new absorption peak formed in CN-UA complex at high UA concentration. • Hydrogen bonds and hydrophobic interactions were the main forces in the complex. • CN-UA complex also exerted considerable antioxidant activities. • UA could improve the bioaccessibility of CN in simulated in vitro digestion.