Rheological properties of wheat flour dough and French bread enriched with wheat bran

- Bran addition led to lower mixing energy but higher elongational viscosity of dough.
- Higher elongational viscosity decreased expansion of bran added dough during proofing.
- Lower proofing expansion led to larger bread densities of fibres enriched breads.
- Firmer texture of fibres enriched breads was mainly due to increased density.
- For same overall fibre level, varying bran size reduces negative effects on texture.

Wheat flour doughs were elaborated with wheat-bran in various contents, up to 20%, and particle sizes of fractions, in order to study the specific role of rheological properties in processing high fibre breads. The addition of wheat bran, especially more than 10%, decreased the specific mechanical energy developed by the mixer, which was attributed to a deficient formation of the gluten network. It increased the elongational viscosity of the dough, measured by biaxial extension tests, likely through a solid particles effect. These changes explained the lower increase of porosity during proofing, assessed by digital camera and 2D image analysis. The loss of dough stability was rather attributed to the destabilizing effect of bran particles on the films separating gas bubbles. The resulting changes of bread texture, determined by image analysis and mechanical testing of breads, including crust and crumb, were governed by bread density, which was established at the end of proofing. These results help to understand the impact of wheat bran on dough rheological properties in order to design French breads with increased fibre content.