Effect of Combined Modification with Xanthan Gum and Docosahexaenoic Acid on the Antigenicity and Structural Characteristics of β-Lactoglobulin

β-Lactoglobulin (β-LG) can cause severe allergic reactions. In this study, the effects of combined modification of β-LG with xanthan gum (XG) and docosahexaenoic acid (DHA) on its antigenicity and structural characteristics were investigated. DHA-β-LG and DHA-β-LG-XG complexes were obtained through non-covalent binding. Their antigenicity and structural characterization were carried out using indirect competitive enzyme linked immunosorbent assay, particle size analysis, three-dimensional fluorescence spectroscopy, Fourier transform infrared (FTIR) spectroscopy, simultaneous fluorescence spectroscopy, ultraviolet-visible absorption spectroscopy and molecular docking. The results showed that the antigenicity of the ternary complex was significantly reduced compared with those of β-LG and the binary complex (P < 0.05). The highest inhibition rate, (24.81 ± 0.27)%, of immunoglobulin G (IgG) binding capacity was observed at 2.5 mg/mL XG concentration. The ternary complex was more stable than the binary complex. As the concentration of XG increased, the particle size of the ternary complex increased and then decreased. Under the coexistence of XG and DHA, the relative contents of β-sheet and β-turn increased, and the relative contents of α-helix and random coil decreased. Furthermore, the exposure levels of both fluorophores and peptide bonds in β-LG showed a linear positive correlation with XG concentration. XG was inserted into the only hydrophobic cavity of β-LG, and DHA bound to the hydrophobic pocket on the surface of β-LG. Both XG and DHA formed the ternary complex with β-LG through hydrogen bonding, electrostatic interactions, and hydrophobic interactions. These structural changes affect the antigen binding epitopes of β-LG, thereby reducing its antigenicity.