Stabilization Effect of Ternary Covalent Complexes with Different Grafting Sequences on Blueberry Anthocyanins

In this study, covalent complexes (WPI-GG-TP and WPI-TP-GG) of whey protein isolate (WPI), gellan gum (GG) and tea polyphenol (TP) with different grafting sequences were synthesized by Maillard grafting and alkali treatment. Fourier transform infrared (FTIR) spectroscopy, fluorescence spectroscopy, and ultraviolet (UV) absorption spectroscopy confirmed the formation of covalent bonds within the ternary complexes. The stabilization effects of the ternary covalent complexes on blueberry anthocyanins (ACNs) were investigated. The WPI-GG-TP complex showed a loading capacity of 21.80% for ACNs, forming nanoparticles with an average particle size of 806.68 nm, while WPI-TP-GG exhibited a loading capacity of 18.68%, forming nanoparticles with an average particle size of 688.08 nm. Thermal analysis showed that the thermal peak temperature of ACNs increased by 2.51 ℃ after loading onto WPI-TP-GG, indicating improved thermal stability of ACNs. The results of antioxidant and stability tests revealed that the WPI-GG-TP complex had higher scavenging capacity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and storage stability after loading with ACNs, while the WPI-TP-GG complex exhibited higher hydroxyl radical scavenging activity, iron reducing power and thermal stability. Specifically, compared with free ACNs, the DPPH radical scavenging activity of WPI-GG-TP-ACNs increased by 29.62%, while the hydroxyl radical scavenging activity and iron reducing power of WPI-TP-GG-ACNs increased by 55.96% and 2.4 times, respectively. These findings provide valuable insights for the development of food delivery systems that enhance functional ingredient stability in the human digestive system.