Influence of Ultrasound on the Mechanism of Conjugation between Epigallocatechin Gallate and Β-Lactoglobulin for Allergenicity Reduction

β-Lactoglobulin (βLg) conjugated with epigallocatechin-3-gallate (EGCG) to form βLg-EGCG conjugates by covalent bonding under alkaline conditions. This conjugation resulted in structural and activity changes, providing a possible approach for allergen desensitization, but with low desensitization efficiency. This study aimed to use ultrasound to improve the conjugation rate of βLg and EGCG and investigate changes in the binding mechanism and functional properties. Scanning electron microscopy revealed βLg-EGCG conjugates to be in the ceoss-linked state, however, it also highlighted fragments of various forms with ultrasonic treatment. Ultrasonic treatment increased the binding affinities (Ka) from 2.5×10 5 M -1 to 6.3×10 5 M -1 and 1.9×10 5 M -1 to 3.0×10 5 M -1 at 4℃ and 44 ℃, respectively. Moreover, ultrasound treatment increased secondary structural changes in βLg in the conjugated state, accompanied by an enhanced inhibition of immunoglobulin E (IgE) attachment and acquisition of antioxidant properties. Ultrasound induced an increase in hydrodynamic diameter and lowered the absolute zeta potential of βLg-EGCG conjugates, resulting in a decrease in thermal stability and an increase in digestibility, as well as foaming and emulsification abilities, improving the application of EGCG conjugation in dairy products.