Effect of tea polyphenols on the dilational rheology of human whole saliva (HWS): Part 1, HWS characterization.

Human whole saliva (HWS) is a physiological secretion that performs a number of essential functions including protection of oral health, lubrication of mouth tissues and food pre-digestion. The complexity of the saliva proteome reflects the unique physiochemical functionality of this biofluid. In addition, saliva influences the transduction of aroma, taste and tactile (mouthfeel) perceptions through the interaction with food and beverages. This work, which is presented as two distinct contributions, reports on the extensive interfacial properties characterization (air-liquid) of saliva either alone or after exposure to tea polyphenols. This first part discusses the complex nature of the salivary film in terms of kinetic and viscoelastic (dilational surface rheology) properties. The formation of the surface film is analyzed with time and explained in terms of the progressively irreversible adsorption of protein fractions of larger molecular weight. The viscoelastic response to appropriate frequency modulation is modelled using a general mixed kinetic model, which satisfactorily reproduces the experimental data in better agreement than the traditional Lucassen diffusive model.