Shear rates during oral and nonoral perception of viscosity of fluid foods

Relationships were established for five sensory methods of oral and nonoral viscosity evaluation between viscosity scores and instrumentally measured dynamic viscosity for model and real Newtonian fluid foods. These relationships were then used to predict the effective shear rates under which the sensory tests were performed. The highest shear rates were predicted for viscosity perception by compression of samples between tongue and palate, and the lowest for pouring the fluid foods from a teaspoon. Mixing with a teaspoon, slurping and swallowing exhibited nearly the same dependencies of apparent shear rates on equivalent instrumental viscosity. All relations were of the hyperbolic type. The resulting relationships between the apparent shear rates and equivalent instrumental viscosity are in good agreement with a similar relationship predicted by Shama and Sherman (1973a) (see Cutler et al. 1983) for oral perception.