Applications Of "Oral" Tribology In Studying Texture And Sensory Perception

Food oral processing is a dynamic process,which involves various oral operations,including ingestion,chewing and mastication,transportation,saliva secretion,bolus formation,swallowing,etc.The food texture is sensed and percepted during this process.A product's rheological properties and its oral tribological behaviour have strong influences on sensory perception,but the mechanisms underpinning such processes are still little known.Recently food rheology study has often been found only satisfactory in interpreting texture sensation during the early part of an eating process.However oral tribology has been seen as a useful technique for food texture study in the recognition of the dominating role of lubrication in oral texture sensation.Here we mainly used a simple experimental set up to measure lubricating properties of different sample systems.The study included the following two parts:(1)Astringency sensation is a specific oral sensation which is described as an unique sensation of dryness and puckering feeling in the mouth.It is one of the main quality factors for red wines,teas.This study focused on the wine astringency and based on the well-known hypothesis that astringency is a tactile sensory feature caused by the salivary protein depletion from the tongue surface and the increased surface friction.Here we used a tribological system to determine the physical properties of different mixture systems.The physical properties included the lubrication behavior(friction coefficient)and morphology of aggregates.A sensory panel was recruited for astringency tests.The results confirm the hypothesis and demonstrate that astringency was a physical stimuli which can be explaied from tribological study.The friction coefficient and sensory results showed a high positive correlation at a sliding speed of 0.075 mm/s(R2=0.899),which provided an appropriate lubrication condition for oral astringency prediction(2)The texture sensation is an important contribute to consumers' acceptance and preference of oral care products(e.g.Toothpaste).A product's rheological properties and its oral tribological behaviour have strong influences on sensory perception,but the mechanisms underpinning such processes are still little known.In this work,a simple experimental set up was used to measure lubricating properties(friction coefficient)as a function of speed for toothpaste samples and their mixtures with either artificial saliva or water.Particle size distribution and rheological properties were also measured along with the lubrication properties.Sensory smoothness and granularity were assessed by a panel using both fingers and tongue.The lubricating properties show significant differences in the boundary regime giving effective discrimination of sample systems.Results from tribological measurements showed a strong linear correlation with the sensory smoothness obtained from taste panel.Further data analysis showed that both rheological properties(viscosity)and particle size distribution strongly influenced the lubrication behaviour and,therefore,contributed to smoothness perception.Results from this work show that combination of rheological and tribological techniques could be a feasible instrumental approach to assess sensory properties of oral care products.