Enhancing oil-water interfacial behavior and emulsion properties of abalone protein hydrolysate-inulin conjugates by pH-shift pretreatment and Maillard reaction

Abalone protein hydrolysate (APH) has potential as a marine-derived food protein ingredient, but its limited ability to form mechanically stable oil-water interfacial films restricts its application in emulsion systems. In this study, APH and inulin were subjected to Maillard reaction under neutral wet-heating or alkaline pH-shift-assisted conditions to determine how pH-dependent structural regulation influences interfacial behavior and emulsion properties. Compared with neutral wet-heating, alkaline treatment suppressed heat-induced aggregation, increased conformational flexibility, and induced rearrangement of the secondary structure of APH. Subsequent covalent conjugation with inulin further modified surface wettability and electrostatic interactions, producing a more dispersed conjugate with improved hydrophilic-hydrophobic balance. These structural and colloidal changes facilitated interfacial penetration and molecular rearrangement, and promoted the formation of a stronger and more deformation-resistant interfacial film. Consequently, emulsions stabilized by the alkaline-treated APH-inulin conjugate exhibited a narrower droplet size distribution, and more pronounced shear-thinning behavior. In contrast, neutral wet-heating favored aggregate formation and limited effective interfacial organization. These findings indicate that alkaline pH modulation not only facilitates APH-inulin conjugation but also regulates the competition between heat-induced aggregation and glycation-associated interfacial assembly, providing a mechanistic basis for improving the functionality of marine protein hydrolysates in food emulsion systems.