Dough aeration and rheology: Part 2. Effects of flour type, mixing speed and total work input on aeration and rheology of bread dough

The aeration and rheological properties of bread doughs prepared from strong and weak flours at various mixing speeds and work inputs in a high-speed laboratory-scale mixer were investigated. Dough aeration was quantified in terms of gas-free dough density and gas void fraction using density measurements, while dough rheology was characterized in terms of the strain hardening index, failure strain and failure stress under large biaxial extensional deformation using the SMS Dough Inflation System. Increasing mixing speed had little effect on the gas-free dough density but increased the void fraction of gas occluded in dough. As mixing progressed, the gas-free dough density initially increased, more dramatically for the weak than the strong flour, before reaching a plateau at approximately 30 kJ kg^-1 energy input. The gas content tended to increase over the range of work inputs tested. For both flours, the strain hardening index, failure strain and failure stress increased with work input initially, followed by a decrease. The absolute values were all higher for the strong flour, while maximum values and the work input at which the maximum occurred depended on the mixing speed. These results show that both aeration and rheological characteristics of dough are dependent on both the total work input and the work input rate. The results also demonstrate the facility of the Dough Inflation System to describe the mechanical development of dough rheology over the course of high-speed mixing.