Easy Viscometer Guide

Purposes of viscosity
measurement

 

Selecting the right viscometer

 

Food products viscosity data

 

Measurement example

This is an example of up-scale, down-scale measurement of step changes in shear rate (hysteresis shear measurement of mayonnaise).

JIS K7117-2 (viscosity measurement method) recommends multipoint measurement (4 or more points) over a wide shear rate area. The figure below shows the results of historical shear measurement of commercially sold mayonnaise from 0.1rpm to 100rpm. The degree of thixotropy can be determined from the area of the hysteresis loop (Fig. A) created by the up-scale and down-scale measurement. The degree that viscosity decreases depending on the shear rate can be determined from the flow analysis (viscosity curve) (Fig. B).

Example of Time Dependent Measurement

Aside from numeric analysis, time dependent measurement based on up-scale, down-scale shear rate step change is a new measurement method which has yielded useful test results on the relative comparison of various tests, shear rate and shear load time relationships which reveal thixotropic (and rheopexic) behavior, and provides definitive preliminary tests of measurement criteria. The left figure in Fig. C shows the state of step change variations of rotation speed. As shown in the bottom figure, with time dependent samples (thixotropic or rheopexic substances) a decreasing change in shear stress dependent on time can be seen. Fig. D and Fig. E are test results of commercially sold mayonnaise. An up-scale and down-scale program was run at rotation speeds, 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50 and 100 rpm for 100 seconds at each speed. Rheopexic behavior (increasing viscosity over time) of standard mayonnaise is apparent at 700-800 seconds (20 rpm).