Samples may be gathered during processing and lab tested by QA staff. Viscosity is measured with Viscometers, Rheometers, or Plastometers. 1 Cream to whipped cream is an example of a rheopectic food. Rheopexy: a material’s viscosity increases when sheared at a constant rate over time.1 Yogurt, pea protein and water, and honey are examples of thixotropic foods. Thixotropy: a material’s viscosity decreases when sheared at a constant rate over time.Its yield value will often make it refuse to pour from the bottle until the bottle is shaken or struck, allowing the catsup to gush freely. Tomato catsup is a good example of this type fluid. Once force is applied the material will flow. Plastic: a material appears to be solid until force is applied.3 Corn starch mixed with water and candy compounds are examples of dilatant foods.

This type of behavior is sometimes called shear-thickening. Dilatant: a material’s viscosity increases as the shear rate increases.1 Cake batter, agar-agar and fruit juice concentrates are examples of psuedoplastic foods. This type of flow behavior is sometimes called shear-thinning.

Psuedoplastic: a material’s viscosity decreases as the shear rate increases.

2 Non-Newtonian fluids can be categorized into five types based on the way a fluid’s viscosity changes in response to variations in shear rate. 2 Examples of non-Newtonian fluids are slurries, pastes and high molecular weight liquids. 2 Examples of Newtonian fluids are water, air, and ethanol.Ī non-Newtonian fluid is any fluid that does not obey the Newtonian relationship between the shear stress and shear rate. This means that a plot of shear stress versus shear rate at a given temperature is a straight line with a constant slope that is independent of the shear rate. Newtonian fluids do not change viscosity with shear.

High viscosity vs low viscosity