Antigenicity of β-lactoglobulin reduced by combining with oleic acid during dynamic high-pressure microfluidization: Multi-spectroscopy and molecule dynamics simulation analysis

Some food components can modulate the antigenicity of beta-lactoglobulin (beta-LG). This study investigated the role of oleic acid (OA) in reducing the antigenicity of beta-LG. The results indicate the antigenicity of beta-LG gradually decreased from 15 (sample with no OA) to 9.86, 7.51, and 6.01 mu g/mL when interacting with OA during dynamic high-pressure rnicrofluidization treatment at 0.1, 80, and 160 MPa. Although binding sites (n) of beta-LG combined with OA at 0.1, 80, and 160 MPa decreased from 0.79 to 0.5 and 0.66, 3-LG had a higher binding affinity (K-a) to OA than that of untreated beta-LG. The values of K-a for beta-LG/OA at 0.1, 80, and 160 MPa were 5.51 x 10(6), 17.43 x 10(6), and 49.75 x 10(6)/12(-1), respectively. The molecule dynamic simulation showed that the OA molecules located at both beta-barrel (site 1) interacted with Lys60, Glu62, and Lys69 and outer surface site 2 consisting of Tyr20, Tyr42, Ser21, Glu157, and His161. Additionally, when binding with OA during the dynamic high-pressure microfluidization treatment, the conformation of beta-LG changed, reflected by the decrease of fluorescence intensity and total sulfhydryl group content, the increase of surface sulfhydryl group content, and secondary structure changes of beta-LG. These results deduce that some epitopes may be masked by OA or modified by the conformational changes, resulting in the decline of antigenicity of beta-LG molecules.