New insights into protein stabilized emulsions captured via neutron and X-ray scattering: An approach with β-lactoglobulin at triacylglyceride-oil/ water interfaces

Hypothesis: To analyze protein stabilized emulsions, SAXS and SANS are emerging techniques capturing oil droplet radius, interfacial coverage and structure. Protein shape, thus protein structure change during interfacial adsorption with partial protein unfolding is detected via SAXS analysis at and below the monolayer concentration for proteins, known as critical interfacial concentration (CIC). SANS determines the same phenomena below and above the CIC, via contrast variation and coarse-grained modelling.Experiments: beta-lactoglobulin concentration dependent SAXS experiments were performed focusing on molecular length scales to characterize protein shape in water, and interfacial structure in emulsions. Complementary SANS experiments with contrast variation via deuterated triacylglyceride-oil provided insight into oil droplet radius, interfacial coverage and structure via data analysis with scattering models and low-resolution shape reconstruction with the DENFERT model.Findings: SAXS and SANS experiments allowed to determine the interfacial structure below and above the CIC, as well as oil droplet radius and interfacial coverage. These findings were identified via Q(-4) Porod scattering at low-Q, protein scattering at high Q, and a Q(-2) scattering of the interface. Since SANS with accurate contrast variation highlights the interface in comparison to other techniques like FTIR, the presented results show a high impact to understand interfaces in emulsions.