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

Abstract

Some food components can modulate the antigenicity of β-lactoglobulin (β-LG). This study investigated the role of oleic acid (OA) in reducing the antigenicity of β-LG. The results indicate the antigenicity of β-LG gradually decreased from 15 (sample with no OA) to 9.86, 7.51, and 6.01 µg/mL when interacting with OA during dynamic high-pressure microfluidization treatment at 0.1, 80, and 160 MPa. Although binding sites (n) of β-LG combined with OA at 0.1, 80, and 160 MPa decreased from 0.79 to 0.5 and 0.66, β-LG had a higher binding affinity (Ka) to OA than that of untreated β-LG. The values of Ka for β-LG/OA at 0.1, 80, and 160 MPa were 5.51 × 106, 17.43 × 106, and 49.75 × 106M-1, respectively. The molecule dynamic simulation showed that the OA molecules located at both β-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 β-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 β-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 β-LG molecules.