Effect of plant-based compounds on mucous boundary layer lubrication during tribological contact

Plant-based proteins offer a higher protein-to-CO2 emission ratio compared to animal proteins. However, their sensory attributes are often less palatable, largely due to the presence of polyphenols, which can evoke an astringent sensation. Polyphenols interact with salivary proteins, altering lubrication and mouthfeel. This study explores the effect of two plant-based compounds, fava bean protein isolate and tannic acid (TA), on the lubricating properties and structure of mucous boundary layers using a novel methodology combining quartz crystal microbalance with dissipation, atomic force microscopy, tribometry and fluorescence microscopy.

Results revealed that bovine submaxillary mucins (BSM) adsorb onto PDMS, forming a hydrated layer with excellent lubricating properties. Fava binds to BSM and PDMS surfaces, forming a hydrated layer that sustains lubrication. In contrast, tannic acid on BSM causes mucin aggregation, destabilizing the adsorbed layer and impairing the mucins’ ability to bind onto PDMS. Shear stresses during sliding of a PDMS probe on the destabilized layer results in a visible damage scar indicating boundary layer removal. This study provides insights into the molecular-level mechanisms influencing oral lubrication, emphasizing the importance of tribological assessment in developing polyphenol-rich plant-based foods.