Selective modification of wheat bran affects its impact on gluten-starch dough rheology, microstructure and bread volume

Wheat bran incorporation in bread has multiple health benefits, but also a detrimental effect on overall bread quality. Bran is hypothesised to withdraw water from gluten, resulting in less optimal viscoelastic dough properties and a lower gas retention capacity, in turn resulting in a decreased bread loaf volume. In this study, wheat bran samples having different water retention capacities were produced and used to investigate this hypothesis. Gluten-starch model systems were used and the effect of substitution of part of the starch by bran in combination with different water absorptions and mixing times was evaluated. The properties of the gluten network in the doughs were investigated using rheological and microstructural analyses and these properties were linked to the final bread loaf volume. A proper gluten network microstructure, as visualised with CLSM, could be achieved in the presence of wheat bran. However, significant effects of the type of wheat bran, water absorption and mixing time on dough rheology and loaf volume were observed. Wheat bran addition decreased the strain hardening of dough despite optimisation of water absorption and mixing time. The deleterious effect of wheat bran on dough rheology increased by adding modified wheat bran with high water retention capacity and surface area. The results indicate that dynamic water redistribution after mixing and gas cell incorporation can have an effect on dough rheology when wheat bran is added to dough. The strain hardening behaviour of dough proved itself a valuable predictor of bread loaf volume also in the presence of (modified) wheat bran.