Green development of whey protein-based complex system for the intestinal delivery of curcumin: Focus on formation mechanism, stability, and in vitro digestive characteristics.

This study delves into the feasibility of developing an intestinal delivery system for curcumin using whey protein as the wall material, employing a simple and eco-friendly (without using organic solvents) pH-induced protein-polyphenol co-assembly strategy. The results indicate that stable complex formed under curcumin concentrations ranging from 0.1 to 0.4 g/L (screened by the preliminary experiment) with particle size between 269 and 287 nm, zeta potential around -38 mV, and curcumin loading capacity ranging from 3.61 to 9.14 mg/g. Curcumin primarily interacts with whey protein through hydrophobic interactions and hydrogen bonds, as confirmed by FT-IR spectroscopy and molecular docking analysis. Curcumin has a different affinity to proteins ranked as bovine serum albumin (BSA) > β-lactoglobulin (β-LG) > α-lactalbumin (α-LA). Curcumin exists in an amorphous state within the protein, which also increases the surface hydrophobicity of the protein (from 565 to 687 AU) and leads to quenching intrinsic fluorescence of the protein. The binding of curcumin causes a transition from random coil to β-sheet in the protein's secondary structure but has a limited impact on its tertiary structure. Stability analysis shows that the complex remains stable in environments with 100-500 mM NaCl and heat treatment at 60-90 °C. In vitro digestion results indicate that the complex aggregates during simulated gastric fluid digestion and decompose during simulated intestinal fluid digestion, effectively enhancing the bioaccessibility of free curcumin by 60 % (P < 0.05). This study provides a theoretical basis for the green processing of protein-based oral delivery systems for lipophilic compounds.