OSCILLATORY RHEOMETRY - THE NECESSITY FOR SAMPLE TEMPERATURE CORRECTION

Preliminary results using an oscillatory probe rheometer to follow sol to gel transformations of pasted starch gave illogical results. G '' appeared to increase instead of decrease, as would be expected for a g elling sol. The increase was dramatic at high temperatures. In many in stances the viscosity loss values (eta') were negative, which is physi cally impossible. Therefore, the equations used were examined for a so urce of error. It was found that no temperature correction was made fo r probe frequency in the test sample. Use of the temperature correctio n for probe frequency in the sample along with the equations provided with the instrument showed that the oscillatory probe rheometer effect ively measured viscous and viscoelastic properties of starch gel syste ms throughout the sol to gel transformation.