The primary requirement for the industrial use of many commercial food emulsions lies in their stability, a critical factor for consumer acceptance. This stability, along with the development of suitable microstructural and rheological properties, is vital for achieving and maintaining the desired texture and sensory qualities. Extensive research has aimed to correlate emulsion stability with its rheology and microstructure. Nonetheless, a deep understanding of nanoscale interfacial behaviour is also essential for enhancing properties at both microscale (e.g. droplet size distribution and microstructure) and macroscale (e.g. rheology of the bulk and emulsion stability).

In emulsions (and foams) stabilized by biopolymers, both the bulk phases and the interfaces exhibit a complex microstructure. Surface active biopolymers, such as proteins and certain polysaccharides, tend to assemble into 2D gel-like structures upon adsorption at the interface. These structures confer significant surface rheological properties, which can even dominate the macroscopic dynamics of the system. The response of these complex fluid-fluid interfaces to an applied deformation is often highly non-linear, either to large deformations (e.g. during production and processing) or even to small deformations, as a result of changes in the interfacial 2D microstructure.

This presentation will highlight research on both linear and nonlinear rheology of complex interfaces and discuss the latest advances available for analyzing and modeling nonlinear interfacial rheology data.

In addition, a similar rheological analysis for protein-stabilized emulsions will be reviewed, in order to explore possible links between interfacial shear rheology and emulsion rheology, as well as their connections with emulsion microstructural parameters and emulsion stability. This approach can be useful to overcome one of the main challenges in emulsion technology, which is to tailor the interfaces that allow the development of optimal emulsion microstructure and stability.