• Fat;
  • saliva;
  • sensory;
  • surfactants;
  • texture;
  • tribology


The role of fat content and type of surfactant for oral friction processes and texture perception of oil-in-water emulsions was assessed. Emulsions at 22% and 33% fat content containing either sodium caseinate or a sucrose ester as emulsifier were compared with viscosity-adapted aqueous solutions of dextran using both sensory evaluation and friction coefficient measurements on a tongue-palate contact model. The impact of saliva on the emulsion droplet size distribution was studied using tribology, differential interference contrast microscopy and light diffraction measurements. Emulsions at 33% and the corresponding iso-viscous aqueous solutions were discriminated in the sensory experiment whereas emulsions at 22% were not. Friction was significantly different for emulsions at 33% and the corresponding iso-viscous aqueous solutions. The difference was not significant for emulsions with 22% fat level when compared with the iso-viscous aqueous solutions. Saliva significantly decreased the friction coefficient of emulsions depending on the surfactant and amount of fat used.