THE INFLUENCE OF TURBULENT FLOW ON THE SENSORY ASSESSMENT OF VISCOSITY IN THE MOUTH.

Low viscosity Newtonian fluids exhibit turbulence in a cone-plate viscometer at high rates of shear which are comparable to those operating in the mouth during sensory assessment of the viscosity of the same fluids. Saliva reduces this effect to some small extent, possibly due to its content of mucin and other proteinaceous substances. The net result is that these fluids appear to have a higher viscosity in the mouth than when they are examined in a viscometer at low rates of shear. Higher viscosity non-Newtonian food materials such as Carnation milk and ice cream do not exhibit turbulent flow, and the only effect exerted by saliva is a reduction in the viscosity at all rates of shear.