Glycation regulation between dual-natural milk-derived proteins and fucoidan by dielectric barrier discharge-cold plasma and its potential for delivery of astaxanthin

Milk proteins are attractive building blocks for food-grade delivery systems due to their biocompatibility and versatile functionality. However, their structural instability and limited protection capacity for lipophilic bioactives restrict broader applications. In this study, β-lactoglobulin fibrils (β-LGF) and β-casein (β-CN) were self-assembled to construct a dual-natural milk-protein complex, followed by dielectric barrier discharge cold plasma (DBD-CP)-assisted glycation with fucoidan (FD) to develop a novel protein-polysaccharide conjugate for astaxanthin (AST) delivery. The structural characteristic, physicochemical property, antioxidant activity, and emulsifying performance of the conjugate were systematically investigated. The β-LGF/β-CN complex at a mass ratio of 1:1 exhibited optimal properties, including reduced particle size, enhanced thermal stability, increased apparent viscosity, and the highest DPPH radical scavenging activity (21.05%). CP-assisted glycation significantly increased the degree of glycation from 9.83% to 18.07%, accompanied by the increased β-sheet content, strengthened intermolecular interactions, and formation of high-molecular-weight conjugates. The LGF-CN-FD conjugate showed superior antioxidant capacity and structural stability. AST-loaded emulsions stabilized by the conjugate achieved the highest encapsulation efficiency (80.57%) and loading capacity (10.73%). In vitro digestion demonstrated enhanced gastric protection (63.25% AST retention) and improved bioaccessibility (51.07%). This work demonstrates that CP-assisted glycation effectively tailors the structure and functionality of dual milk-protein assemblies, providing a simple and efficient strategy to design robust colloidal delivery systems for lipophilic bioactives in functional foods.