Stability, disperse and rheological properties of oil-in-water emulsions prepared using poloxamer 188-xanthan gum mixtures.

Oil-in-water (o/w) emulsions are essential systems in pharmaceutical, cosmetic, and food industries, with an emerging role in tissue engineering and regenerative medicine. In this work, mixtures of poloxamer 188 (P188), a nonionic surfactant with a unique structure and biological properties, and xanthan gum (XG), a well-known natural thickener, were employed for the development of the stable 30% (w/w) sunflower o/w emulsions, with a rotor-stator homogenizer, during the storage period set at 21 days. To evaluate the potential of P188 and XG mixtures to prepare stable emulsions, surface tension properties of their aqueous solutions, creaming stability, disperse, and rheological properties of the emulsions were studied. The investigation of the surface-tension properties indicated that there are no attractive interactions between these compounds. The analysis of the creaming stability during the storage period showed that the addition of XG in concentrations below 0.10% increased gravitational separation, most probably due to the effect of depletion flocculation. The most stable emulsions had XG in concentrations of 0.20% and higher, well above the overlap concentration of the thickener. The droplet size and size distribution analysis, performed 1 and 21 days after the emulsion preparation, showed less significant change in the Sauter mean diameter and size distribution during the storage in emulsions with XG concentrations of 0.20% and higher. The rheological investigations indicated that XG in concentrations above 0.20% yields emulsions with a semi-structured viscoelastic matrix capable of resisting flow, deformation, and creaming. All possible mechanisms involved in the observed phenomena in this work were thoroughly discussed.