Colloidal stabilization of oil-in-water emulsions in aqueous partially saponified poly(vinyl alcohol) solutions of low concentration as continuous phase.

Water-soluble polymers (WSPs) are normally used as thickeners for colloidal stabilization of oil-in-water (O/W) emulsions because the creaming of O/W emulsions is prevented by increasing the viscosity of continuous phase. We examine here the effect of WSPs such as polyethylene glycol (PEG), polyvinylpyrrolidone (PVP) and partially saponified poly(vinyl alcohol) (ps-PVA) on the colloidal stabilization of O/W emulsions prepared in aqueous solutions of low concentration WSP (0.5 wt%) as continuous phase. We found that the colloidal stability of WSP-O/W emulsions prepared by mixing soybean oil (SOY) and aqueous ps-PVA solution with a rotor-stator homogenizer (ps-PVA-SOY/W emulsion) was remarkably high compared to other WSPs-SOY/W emulsions, even if the viscosity of aqueous ps-PVA solutions that we applied in this work was almost same with that of water. In particular, the ps-PVA with lower saponification degree was more effective for colloidal stabilization of O/W emulsions than other WSPs. The higher colloidal stability of ps-PVA-SOY/W emulsions prepared using ps-PVA with lower saponification degree is most likely due to the decrease in interfacial tension between oil and water by ps-PVA with lower saponification degree, and the resulting formation of smaller-sized oil droplets.