Influence of salt ionic strength on the freeze-thaw stability of sodium caseinate-modified solid lipid particle-stabilized pickering emulsions: regulation of lipid crystallization behavior and interfacial rheology.

In recent years, sodium caseinate-stabilized solid lipid particles (NaCas-SLPs) have shown potential in stabilizing Pickering emulsions, yet the impact of salts on their freeze-thaw stability remains debated. This study elucidates how NaCl modulates the interfacial assembly and crystallization behavior of NaCas-SLPs, and consequently reshapes the freeze-thaw stability and rheological performance of the resulting Pickering emulsions. The results demonstrated that NaCl regulated particle size, ζ-potential, and contact angle, thereby affecting interfacial protein adsorption and fat crystallization behaviors. These changes enabled SLP rearrangement at the oil-water interface and the formation of a more compact and stable interfacial structure. In addition, closely packed droplets and inter-droplet crystal bridging contributed to a dual stabilization mechanism. DSC and XRD analyses confirmed that NaCl effectively restricted lipid molecular migration and rearrangement during freeze-thaw cycling, facilitating the transformation toward more thermodynamically stable β crystals. Meanwhile, the strengthened interfacial layer and crystal network enhanced viscoelasticity and improved resistance to droplet aggregation and coalescence. These findings provide fundamental insight into ion-mediated stabilization mechanisms and highlight the potential of NaCas-SLPs for developing freeze-thaw resistant food emulsions.