Abstract
The viscoelastic behaviour of native potato starch dispersions was studied using dynamic viscoelastic measurements. The influence of various shear and heat treatments of gelatinized starch pastes were compared in the concentration range 4–10%. Heating had a minor effect compared to the effect of shear treatment. The complex modulus (G∗) decreased to about 5% of its maximum value when the starch pastes were sheared during the heating cycle, whereas heating alone resulted in a decrease to about 60% of the maximum G∗ value. Shear also caused an increase in the phase angle and characteristic changes were observed with regard to frequency and strain dependencies. When samples were prepared in a Brabender viscograph, the shear induced changes took place early in the pasting cycle. The characteristics of the concentration dependence differed due to the shear history of the sample. Peculiar concentration dependencies, some even negative, could be obtained from samples with different shear histories. The results imply that even moderate shear treatment gives rise to structure changes which are reflected by a transition in the type of the viscoelastic behaviour.
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