QC will implement this procedure as the control point for each batch. R&D must determine whether a single viscosity measurement value taken from the flow curve in Figure 3a is sufficient to guarantee successful processing. It can also correlate with consumer experience when spooning the frozen product and possibly even sensation in your mouth when eating ice cream. This measurement is relevant to start up torque needed for pumps in processing the mix. Yield stress is a measure of how much force is needed to initiate flow. The objective of the temperature test is to observe how viscosity behavior changes because of cooking and refrigerating. Other tests that R&D may perform include temperature profiling (Figure 3b) and Yield Stress determination (Figure 3c). Viscosity may approach an asymptotic minimum value at high rotational speed. Figure 3a shows a viscosity flow curve which illustrates how viscosity decreases as spindle speed increases, also referred to as “shear rate” when testing in a coax cylinder system. This degree of change could be used as a control parameter in QC testing to determine whether the mix has reached its end condition prior to freezing. Most formulations will show some decrease in viscosity which is referred to as “pseudoplastic” or “shear thinning” behavior.Īs mentioned earlier, “thicker” formulations may exhibit greater change in viscosity. temperature profile, and possibly yield stress determination. The most basic test involves rotating the spindle at increasing speed to observe how viscosity changes. Typical tests in R&D will include viscosity flow curve, viscosity vs. Mix material inside the circumference of vane shears against material outside, providing a true viscosity measurement of the formulation loaded with particles.

The vane spindle can rotate in a beaker for a quick quality control (QC) test or mating chamber for characterization of flow behavior by R&D. Vanes allow plenty of space for the pieces to migrate freely as the spindle rotates. What happens when you add fruit pieces to the mix?Īddition of fruit pieces and other particulate items to the mix has led to use of vane spindle to measure viscosity of new formulations.

Viscosity tests