Study of the anomalous capillary Bagley factor behavior of three types of wheat flour doughs at two moisture contents

The flow properties of wheat flour dough were evaluated using a capillary rheometer as a function of flour type (soft, hard and durum wheat flours) and dough moisture content (43 and 48% wb). The desctiption of experimental flow properties was conducted using the classical Bagley approach and assuming linear relationships between pressure drop and L/D ratio (R-2 ranging from 0.795 to 0.993). The entrance pressure drop (P-0) increased (from 40 to 18 70 kPa) with an increase in shear rate (from 40 to 1333 s(-1)) and a decrease in dough moisture content. Shear viscosities (7 to 160 Pa.s) and elongational viscosities (41 to 2840 kPa.s) demonstrated shear-thinning behaviors that were characterized using power law models. Elongational and shear flows were compared by the Trouton ratio. ne characterization of the capillary flow behavior for wheat flour dough was then discussed in regard with a possible nonlinear behavior of Bagley plots and related to possible changes in dough structure (i.e. dough hardening, strain hardening and dough deorientation).