Upon consumption, food emulsions, e.g. milk, margarine, mayonnaise, undergo different processes, including mixing with saliva. The aim of the current study was to investigate the role of saliva and saliva components on the behaviour of food emulsions in the oral cavity. In this project, different physical chemistry and biochemical techniques were used to study the saliva-emulsion mixture and to characterize saliva components interacting with emulsion droplets. The importance of the saliva-droplet interaction, in particular the saliva-induced flocculation, on the perception of emulsions was demonstrated with a sensory paneling study. This study highlighted the mechanism of emulsion flocculation upon mixing with saliva and showed that flocculation can be controlled by varying several emulsion parameters (e.g. charge, pH, ionic strength). Moreover, by investigating the interaction between emulsions and saliva we started to gain insights into the sensory perception of emulsions.
When emulsions meet saliva
This thesis investigated the influence of saliva on emulsions properties, the mechanism of saliva-induced emulsion flocculation and the role in sensory perception. Firstly, we separately analyzed the effect of different parameters related to both emulsions and saliva. This approach shows that emulsion and saliva properties affect the flocculation behavior of emulsions/saliva mixtures.
Secondly, to investigate the nature of the flocculation, we characterized the salivary protein composition on the emulsion droplets in emulsion/saliva mixture. The results indicate that the emulsifying protein at the oil-water interface determines the salivary components associated with the droplets. Flocculation was hypothesized to be driven by a complex formation involving specific interactions and electrostatic attraction between salivary peptides/proteins and the emulsifying proteins at the droplets surface.
The importance of the saliva-induced droplet flocculation was demonstrated with a sensory paneling study and may help to improve our understanding of the sensory perception of emulsions.