Enhanced calcium and thermal stability of whey protein hydrolysate stabilized emulsions by ultrasound-assisted glycosylation: Influence of the degree of glycosylation

Glycosylation can enhance the thermal stability and ionic tolerance of protein hydrolysate emulsions. Ultrasound-assisted wet-heat glycosylation (UA) and precise control over the degree of glycosylation (DG) are crucial for optimizing the modification effects. This study investigated the mechanisms underlying the influence of UA on the macroscopic stability of whey protein hydrolysate (WPH)-xylose (XL) conjugate emulsions. WPH-XL complexes (NWPH-XL) and wet-heat glycosylation (WH) served as controls. Both UA and WH reduced the interfacial adsorption capacity, interfacial interactions, and interfacial strength of WPH, with the extent of these reductions increasing with increasing DG. When DG up to 50 %, an "active" state characterized by high surface hydrophobicity and molecular flexibility, potentially promoting emulsion droplet aggregation during sterilization and storage. Notably, compared to WH, UA accelerated the reaction rate, inhibited the formation of AGEs, and improved the interfacial adsorption capacity, interfacial interactions, and interfacial strength of the conjugates by dissociating large aggregates. Consequently, UA conjugates with DG of about 20 % exhibited the strongest interfacial layer stability, effectively resisting oil droplet aggregation induced by 15 mM Ca²⁺ and sterilization at 121 °C (emulsion particle size of 276 nm). Taken together, these findings elucidated the mechanisms by which UA improves the stability of WPH-based complex emulsion systems from the perspective of interfacial behavior and highlighted the advantages of UA in enhancing the environmental tolerance of protein hydrolysates, expanding their potential applications in food emulsions.