Abstract: Proteins are easily self-assembled into different aggregates during thermal processing. The surface structure and rheological properties of different protein aggregates have significant effects on the stability and digestibility of emulsions stabilized by them. To explore the interfacial behavior of β-lactoglobulin aggregates, in this study, β-lactoglobulin (β-lg) aggregates, β-lg nanoparticle aggregates (β-lg NP) and β-lg fibrillar aggregates (β-lg F) were prepared by controlling the heating temperature and pH, and their morphology was evaluated. The adsorption kinetics and the displacement behavior of protein films by bile salts (BSs) at the oil (decane)/water interface were studied using particle tracking microrheology and interfacial dilatational rheology. The digestion characteristics of emulsions stabilized by these protein aggregates were studied using an in vitro digestion model. It was found that protein diffusion to the interface became faster and the interfacial viscoelasticity became stronger with increasing protein concentration. β-lg NP and β-lg F could be adsorbed faster than native β-lg onto the interface, forming interfacial films with higher elasticity. In the case of protein displacement, β-lg NP had the strongest ability to resist bile salt substitution, while native β-lg had the weakest ability, which was consistent with the results from in vitro digestion experiments.

Key words: interfacial behaviour; β-lactoglobulin aggregates; particle tracking microrheology; interfacial dilatational rheology