Modelling the Developmental Rheology of Wheat-Flour Dough using Extension Tests

Modern cereal science has progressed to the point where a more detailed and explicit understanding of the rheological properties of wheat-flour dough at the molecular level is required in order to improve plant breeding methodologies, the manufacturing of wheat-flour dough products and the assessment of wheat and wheat-flour quality. The formulation of molecular models provides a basis for predictive tests that can be combined with other protocols. The actual modelling must, in turn, be based on experiments which directly monitor the changing rheology of the dough which occurs during mixing, as it is this evolving rheology which in effect monitors the dough at a molecular level. There are various ways in which this can be done. The perspective adopted here is that, at least on a MixographTM, the mixing of the dough can be viewed as a series of extension tests. It therefore follows that one way to monitor the evolving rheology of a wheat-flour dough during mixing is to perform extension tests on the dough at various stages during the mixing. The results obtained from such experiments are reported in this paper. They show how the study of the evolving rheology of a wheat-flour dough, during mixing with varying amounts of added water, in effect monitors the molecular processes occurring during mixing in terms of the behaviour of the bonded and unbonded water within the dough. In addition, these results yield confirming evidence for the hypothesis, tentatively proposed by various authors, that the bandwidth of a Mixogram is a key (qualitative) characteristic of a dough for assessing its strength. Together, both these conclusions imply that, as well as a measure of the strength and quality of the dough being mixed, the variation in the bandwidth of a Mixogram is indicative of the role played by the added water during the mixing.