Effect of surfactants on the interfacial behaviors of diacylglycerol-based solid lipid nanoparticles and physical stability of W/O emulsion

The influence of surfactants (Span 80, Span 60, PGPR and sodium caseinate) on the stability of W/O emulsions stabilized by diacylglycerol (DAG)-based solid Lipid nanoparticles (SLN) was investigated. DAG-based SLN showed phase separation at high NaCl concentration and acidic pH although the SLN-stabilized W/O emulsion was minimally affected. Span 80 increased the hydrophobicity whereas Span 60 increased the hydrophilicity of SLN. With concentration close to CMC, both Span surfactants caused detachment of SLN from interface and reduced emulsion stability. Nonetheless, addition of a small amount (0.1 wt%) of Span surfactants increased the interfacial modulus. The co-adsorption of SLN and PGPR at the oil-water interface promoted the formation of denser network structure and higher interfacial elasticity, which enhanced the emulsion rigidity and freeze-thaw stability. Sodium caseinate (NaCAS) showed intense competition with particles for adsorption at the interface and caused emulsion destabilization. Consequently, the NaCl release rate was directly influenced by the emulsion stability and the interaction between surfactants with SLN. The results have important implications for applying DAG nanoparticles as stabilizers in W/O emulsions with tailoring interfacial rigidity and water-soluble component release behaviors.