Cold plasma promoted complexation of chlorogenic acid with β-lactoglobulin/α-lactalbumin: Structural characterization, functionality and binding mechanism

Cold plasma (CP) promoted the complexation between chlorogenic acid (CA) and β-lactoglobulin (β-LG) as well as α-lactalbumin (α-LA). In the presence of chemical dissociants (SDS and urea), CP increased the bound CA content onto β-LG and α-LA by more than 4-fold, demonstrating tighter CA association. Molecular docking revealed hydrogen bonds as the dominant force for α-LA-CA binding, while hydrophobic interactions govern β-LG-CA combination. Reactive species produced during CP treatment were quantified. CP-induced complexes exhibited only a slight band shift in electrophoresis, and LC-MS analysis confirmed no covalent adducts existed within the complexes. Circular dichroism, FTIR, UV–vis, and fluorescence spectra, and surface hydrophobicity determination, demonstrated that CP effectively modified the secondary structure and surface microenvironment of proteins, leading to an increase in the binding of CA. Quantitative analyses of carbonyl groups, free sulfhydryl, and free amino groups confirmed mild protein oxidation induced by CP, exposing more binding sites for CA. Furthermore, owing to CP-induced protein modification and enhanced CA interaction, CP-induced complexes showed the larger particle size and zeta-potential, and superior antioxidant capacity. This study clarifies the non-covalent interaction mechanism of CP-induced β-LG/α-LA–CA complexes and provides a theoretical basis for the green preparation of high-performance functional biocomposites.