Effect of loading history on visco-elastic potato starch gel

In this work gelatinised potato starch is shown to retain the memory of past loading history. It exhibits a visco-elastic response which does not depend solely on instantaneous conditions. A simple squeeze flow experiment is performed, where loading is done in two steps with a time lag tau similar to seconds between the steps. The effect on the strain, of varying 7 is reproduced by a three element visco-elastic solid model. Complexity is introduced through a generalised calculus approach by incorporating a non -integer order time derivative in the viscosity equation. A strain hardening proportional to the time lag between the two loading steps is also incorporated. This model reproduces the three salient features observed in the experiment, namely - the memory effect, slight initial oscillations in the strain as well as the long-time solid-like response. Dynamic visco-elasticity of the sample is also reported. (C) 2015 Elsevier B.V. All rights reserved.