Unveiling the microstructural dynamics of Pickering emulsions: A microrheological approach.

Understanding food with complex structures, in particular emulsions, remains a challenge for food professionals. Emulsions exhibit rheological behaviors ranging from the Newtonian to the viscoelastic range when measuring deformation under stress. Unfortunately, they fail to correlate particle forces or interactions, microstructure, and bulk mechanical properties. This review describes the concept of microrheology (MR), an emerging non-invasive technique, and its application in food emulsions, specifically Pickering emulsions (PEs), highlighting the novelty of these techniques over the conventional bulk rheology. It measures spatial mechanical properties on the micron scale by embedding tracer particles in complex fluids. MR consists of passive and active methods, and both of which are elucidated in this review. Active MR manipulates tracer particles using external forces to probe materials with higher rigidity and clarify local rheological characteristics. Passive MR utilizes the spontaneous Brownian motion of particles to illuminate the mechanical properties of soft materials. Among passive methods, diffusing wave spectroscopy (DWS) stands out for its ability to characterize PEs by analyzing light scattering fluctuations to reveal the material's viscoelastic properties across different length scales. This technique facilitates the extraction of many parameters, offering insights into the microstructural behaviors of emulsions that bulk rheology often overlooks. Microrheological measurements have demonstrated their effectiveness in analyzing the stability and dynamic properties of PEs, underscoring their potential for exploring the complex microstructural behaviors of these systems.