Grafting phenolics onto milk protein via conjugated polymerization for delivery of multiple functionalities: Synthesis and characterization

A synthetic scenario for functionalization of beta-lactoglobulin (beta Lg) with polymeric units containing caffeic acid (beta Lg-polyCA) was developed; and all intermediates and final products were structurally confirmed using nuclear magnetic resonance spectroscopy, matrix assisted laser desorption ionization time-of-flight mass spectrometry, and physico-chemically characterized using differential scanning calorimetry and circular dichroism. The antioxidant properties and emulsion stability of beta Lg, beta Lg-CA conjugate and beta Lg-polyCA based systems containing high percentage of fish oil (50%) were evaluated; and beta Lg-polyCA presented the highest antioxidant and free radical-scavenging activity based on DPPH, ABTS and HS scavenging assays (92.4, 87.92 and 67.35% respectively). Thiobarbituric acid (TBARS) WA demonstrated that compared to native beta Lg, beta Lg-polyCA afford up 4-5 fold of inhibition of oxidative rancidity and displayed drastic secondary structure changes. Compared to native beta Lg based emulsions, beta Lg-polyCA had larger oil droplet sizes, stronger negative zeta potentials ( - 69.9 my), narrower size distributions (PDI: 0.22) and less creaming index.