A product's resistance to flow is critical to processing applications such as pumping, filling and molding. In addition, viscosity affects product attributes like mouthfeel, pourability, cling and emulsion stability. Ross Clark, section manager applied rheology, Kelco Div., San Diego., reports a correlation between instrumentation and organoleptic evaluations when ranking the viscosity of instant beverages. However, he feels viscosity alone may not tell the whole story. According to Richards, shear stress is defined as the force acting in the plane of the fluid.
Shear rate is the velocity gradient of the fluid between the plates.
The shear rate takes into account the distance between the plates, an important consideration in viscosity measurement. Water at 20 degrees Celcius has a viscosity of one mPas. If these conditions are not met, the measurements will be relative rather than absolute. The units of kinetic viscosity are millimeters squared per second, stokes or centistokes. Going with the flow Foods exhibit different types of flow.