Roles of NaCl in Enhancing the Stability of Water-in-Oil High Internal Phase Emulsions

This study constructed a novel method to develop ultrastable water-in-oil high internal phase emulsions (W/O HIPEs) by using polyglycerol polyricinoleate (PGPR) and NaCl. Microstructural observation demonstrated the formation of W/O HIPEs. The addition of NaCl significantly reduced the mean droplet diameter, resulting in denser and more uniform network structures. The textural and rheological analysis revealed that the W/O HIPEs conformed to the Carreau–Yasuda model (R2 > 0.99) and behaved like a pseudoplastic fluid. The increment in PGPR (4–10 wt %) and NaCl (10–500 mM) significantly enhanced the storage modulus, zero shear viscosity, and deformation resistance of the emulsions. The addition of NaCl (10–500 mM) significantly improved the freeze–thawing stability of W/O HIPEs, with the water-holding capacity (WHC) increasing from 67 to 99% after three freeze–thawing cycles. In the meantime, the W/O HIPEs containing NaCl had good stability when heated at 70, 80, and 90 °C for 30 min, with a WHC of >95%. These findings demonstrated that the presence of NaCl was helpful in developing stable W/O HIPEs, further widening the applications of W/O systems.