Impact of ionic strength on physicochemical stability of o/w emulsions stabilized by Ulva fasciata polysaccharide

The aim of this research was to investigate the effect of ionic strength (Na+ 0.1-0.5 mol/L, Ca2+ 0.01 -0.05 mol/L) on the physicochemical stability of o/w emulsions stabilized by Ulva fasciata polysaccharide. Droplet diameter, Polydispersity Index (PDI), zeta-potential value, microscopic morphology and rheological properties were achieved to investigate the possible stability mechanisms. The results showed that different metal ions had significant effects on the stability of o/w emulsions. When compared the effect of Ca2+ with that of Na+, it was found that Na+ concentration did not have a significant effect on emulsions stability. The results indicated that zeta-potential decreased sharply with increasing calcium ionic strength (CaCl2: 0.01 mol/L -0.05 mol/L) and the minimum zeta-potential value was -27.5 mV, while zeta-potential changed slightly when NaCl (0.1 mol/L -0.5 mol/L) were added. As for z-average size and PDI, they changed significantly with higher valence metallic ions. With increasing NaCl and CaCl2 concentration, the retention rate of R-(+)-Limonene was reduced and emulsions exhibited non-Newtonian behavior. Another interesting result was that the addition of Ca2+ at low concentration (0.01 mol/L - 0.02 mol/L) managed to improve the stability of emulsions. (C) 2017 Elsevier Ltd. All rights reserved.