(a) Strain sweep test. The region of linear viscoelasticity was first assessed. When materials are tested in their linear range, in fact, their characteristics do not depend on the magnitude of the stress ordeforming strain, or the rate of application of the strain (Steffe,1996).
The linear domain limit, determined from the strain sweep test, was 0.05% strain for all the samples. Beyond this limit, both the elastic modulus (G0 ) and the viscous modulus (G00 ) decreased and, as a result, tand increased (curves not reported).
G0 and G00 are parts qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
ðG0 Þ2 þ ðG00 Þ2 Þ, reported in of the complex modulus, G* ðG* ¼ Fig. 3a. In general, beyond the limit of 0.05% strain a progressive dismantling of the original structure of the matrices was observed, indicating that variations in the rheological properties of the different doughs became dependent on the magnitude of the strain imposed.