Aeration During Bread Dough Mixing: I. Effect of Direction and Size of a Pressure Step-change During Mixing on the Turnover of Gas

The aeration of bread dough during mixing has previously been modelled as a balance between gas entrainment and disentrainment into and out of the dough, from which the gas turnover time was determined. This paper tests this model by mixing dough in a high-speed Tweedy-type mixer which undergoes a pressure step-change midway through mixing. The volume of gas entrained in the dough following the pressure change was calculated from its density. The volume of gas entrained was found to reach a steady state much more quickly following a pressure step-decrease than an increase, appearing to signify gas turnover rates over twice as large. Thus, gas disentrainment was found to be enhanced following a pressure step-decrease in a manner not incorporated into the model. The size of the pressure step-decrease did not appear to affect the gas turnover time, but increasing the pressure step-increase size decreased the gas turnover times. The weak flour doughs exhibited higher gas turnover rates during mixing than the strong flour doughs, in both pressure stepchange directions and at all step-sizes