THE RATE-INDEPENDENCE OF THE MIXING OF WHEAT-FLOUR DOUGH TO PEAK DOUGH DEVELOPMENT

When examining quantitatively the material properties of wheat flour d ough? the need arises to model the mixing of the dough in terms of som e constitutive relationship which simulates the changing rheology of t he dough during the mixing. In formulating a mathematical model of the mixing one kev issue is the extent to which the mixing of the dough d isplays, at least with respect to certain mixers, rate-independent cha racteristics. Evidence is presented to support the hypothesis that, at least to first order, the evolving rheology, resulting from the mixin g of a wheat flour dough in a Mixograph(TM) (but not necessarily in so me other recording or commercial mixers), has a clear rate-independent character. When mixed on a variable speed 35 gm Mixograph(TM), flour water dough of constant moisture content, prepared from seven hours of widely differing protein contents, showed statistically significant d ifferences in the number of mixer revolutions required to reach peak d ough development and in their resistance at peak dough development. Fo r each of the flours, the number of revolutions was essentially consta nt at the five different speeds examined, whereas the resistance incre ased gradually (and steadily) as the mixer speed increased. (C) 1998 A cademic Press Limited.