Interactions of chitin nanocrystals with β-lactoglobulin at the oil–water interface, studied by drop shape tensiometry

• Chitin nanocrystals (ChN) can be utilized in Pickering stabilization of emulsions.
• The interactions between ChN and an interface active food protein (β-lactoglobulin) were investigated to mimic a realistic oil–water interface.
• The properties of the oil–water interface were tested using drop shape tensiometry.
• The mixed interfacial film elasticity was the highest at a moderate level of β-lg addition.
• The rate and sequence of adsorption at the interface is critical in determining the final composition.

Particle stabilized emulsions have been gaining increasing attention in the past few years, because of their unique interfacial properties. However, interactions between food grade particles and other surfactants at the interface still need to be understood. In this research, the interfacial properties of chitin nanocrystals (ChN) were studied in the presence of a surface active milk protein, β-lactoglobulin (β-lg), often used to stabilize oil-in-water emulsions. ChN were prepared by acid hydrolysis of chitin. At low pH (pH 3), ChN and β-lg do not interact, as demonstrated by light scattering measurements, and both components carry positive charge. The properties of the interface were tested using drop shape tensiometry. Addition of ChN or β-lg to the aqueous phase reduced the interfacial tension, and β-lg adsorption was characterized with an increase in the interfacial elasticity. When β-lg was added to a solution containing 0.1% ChN, the film elasticity increased first and then decreased with increasing β-lg concentration. The mixed film elasticity was the highest at a combination of 0.1% ChN + 0.01% β-lg, when both molecules were simultaneously added to the aqueous phase. On the other hand, when β-lg was added after ChN, the protein did not affect the properties of the interface, indicating that the ChN (0.1%) equilibrated film was stable and that protein–protein interactions, normally resulting in an increase in the film elasticity, did not occur.

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