Fortification of wheat bread with an alternative source of bean proteins using raw and roasted Phaseolus coccineus flours: Impact on physicochemical, nutritional and quality attributes.

Wheat flour substitution with flours from raw and roasted beans of Phaseolus coccineus at 20 and 30% (flour basis) was studied in breadmaking. The rheological behavior of starch-proteins networks in the composite flour doughs, composition and quality attributes of breads, bread staling events, in vitro starch digestibility of bread crumbs, and volatiles profile, were evaluated using a multi-instrumental analytical approach. According to oscillatory rheological tests, wheat flour substitution with bean flour enhanced the dough's firmness (G′, η*), implying a greater dough resistance to flow and deformation. Nevertheless, the specific volume of breads with roasted beans flour improved, compared to those fortified with raw bean flour, and was comparable to control wheat bread. The texture profile analysis of breads with raw bean flour indicated a greater degree of crumb hardening at the end of storage, despite the lower extent of amylopectin retrogradation, as determined calorimetrically (DSC). FTIR spectroscopy for breads containing bean flour showed little differentiations in the secondary protein structures between fresh and stored crumbs; generally, the β-type structures (β-sheet, aggregates and β-turn) prevailed in all samples at the expense of other secondary conformational elements in the crumb protein networks. The in vitro starch digestibility of fortified bread crumb showed reduced glucose release responses compared to wheat flour bread. The typical "beany" flavor notes of fortified breads were masked using the roasted bean flour; this was corroborated by a modified profile of bread volatiles, resulting in a pleasant sensory appeal for the 20%-substituted product and a more favourable consumer acceptability. [Display omitted] • Wheat bread was fortified (20, 30 %) with flours from raw and roasted Phaseolus coccineus seeds. • All fortifications with bean flours increased water absorption and dough firmness. • The fortified breads showed greater crumb hardening upon storage. • Minor changes in protein conformational elements were noted by FTIR spectroscopy. • Fortified breads with roasted bean flour showed masking of 'beany flavor' notes. [ABSTRACT FROM AUTHOR]