IDENTIFICATION OF STIMULI CONTROLLING THE SENSORY EVALUATION OF VISCOSITY I. <i>Non‐Oral Methods</i>

Abstract

Abstract Flow properties of several liquid and semi‐solid foods were characterized objectively with a coaxial cylinder viscometer. At the same time, a sensory evaluation panel compared the viscosities of these samples by tilting the containers and also by stirring the contents with a spoon. Correlation of the instrumental and sensory evaluation data established the shear stress‐shear rate conditions prevailing during sensory evaluation of viscosity. The stimulus responsible for viscosity evaluation by tilting the container is the shear rate (0.1–40 sec ‐1 ) developed at a shear stress (60–600 dyne cm ‐2 ) related to the flow properties of the sample, whereas in stirring tests the stimulus is the shear stress (10 2 –10 4 dyne cm ‐2 ) developed at a particular rate of shear (90–100 sec ‐1 ). In the latter type of test, the shear rate varies to some degree with the flow characteristics of the sample. Since different stimuli are involved in viscosity assessment by tilting the container or by stirring, it is possible for a series of samples to be given different ranking orders by the two methods of evaluation.