Human capability in the perception of extensional and shear viscosity

Area of Science:

• Rheology
• Human Sensory Perception
• Food Science

Background:

• Shear and extensional deformations are fundamental rheological phenomena with distinct fluid responses.
• Understanding human perception of these properties is crucial for the food industry in product development.

Purpose of the Study:

• To investigate human perception of shear and extensional viscosity.
• To test the hypothesis of different human sensory discrimination mechanisms for these deformations.
• To determine the thresholds for viscosity discrimination.

Main Methods:

• Prepared fluid samples using guar gum and sodium carboxylmethylcellulose (CMC-Na).
• Assessed fluid rheology using shear and extensional rheometers.
• Conducted sensory analysis sessions using magnitude estimation and just-noticeable-difference (JND) assessments.

Main Results:

• Human perception of both shear and extensional viscosity follows Steven's law (power law relationship).
• Humans demonstrated a greater discriminatory capacity for extensional viscosity.
• The just-noticeable-difference (JND) threshold was 9.33% for shear viscosity and 6.20% for extensional viscosity.

Conclusions:

• Human sensory perception of viscosity is deformation-dependent.
• The food industry can leverage these findings to design products with desired textural properties.
• Further research can explore the neural mechanisms underlying these perceptual differences.