Influence of ultrasonic pretreatment on the structure, antioxidant and IgG/IgE binding activity of β-lactoglobulin during digestion in vitro

•Ultrasonic can improve the susceptibility of β-Lg during digestion in vitro.•Ultrasonic-assisted with digestion increased antioxidant activity of β.•Allergenicity of ultrasonicated β-Lg after gastrointestinal digestion was changed. The influence of ultrasonic pretreatment on the structure, antioxidant activity, and IgG/IgE binding activity of β-lactoglobulin (β-Lg) during digestion in vitro were studied by spectroscopy, chromatography and ELISA. After β-Lg was treated by ultrasonic prior to digestion in vitro, the treated β-Lg showed high intrinsic fluorescence emission, more of the hydrolytic products and high antioxidant activity, which depend on the proteolysis promoted by ultrasonic, and produced many small-molecule antioxidant peptides. Native β-Lg was resistant to gastric digestion and retained its allergenicity. However, the allergenicity of ultrasonicated β-Lg after gastric digestion was increased due to ultrasonic promotes the production of peptides with intact structure and immunogenicity. Subsequent gastrointestinal digestion, ultrasonicated β-Lg has a diametrically opposite results because the increase of small peptides with the decreasing of immunogenicity. Therefore, the structural changes of β-Lg by ultrasonic and gastrointestinal digestion were responsible for improving the antioxidant activity and reducing the IgG/IgE binding activity.