Bean Pre-treatment Shapes the Techno-functional and Rheological-Pasting Behaviour of Wheat-Bean Flour Systems

Introduction: Legume flours can improve the nutritional and functional value of cereal products, but their incorporation into wheat matrices depends on particle size, hydration and interfacial properties, and rheological-pasting behaviour. This study compared wheat flour, flours prepared from boiled and soaked beans, and wheat-bean blends as model systems for fermented bakery applications.

Methods: Samples were characterized for particle size distribution, CIE L*a*b* colour, techno-functional properties, foaming and emulsifying behaviour, oscillatory rheology, and pasting characteristics using a Rapid Visco Analyser.

Results and Discussion: The studied systems differed clearly in particle size distribution. Soaked-bean flour contained the highest coarse fraction, with 38.31% retained on the 0.500 mm sieve, whereas boiled-bean flour was mainly retained on the 0.355 mm sieve and wheat flour on the 0.250 mm sieve. Bean pre-treatment also affected colour: the wheat-boiled bean blend showed the highest lightness, while the wheat-soaked bean blend was the darkest and shifted towards positive a* values. The incorporation of bean flour modified functional behaviour, particularly interfacial properties. Bean flours and blends showed higher emulsifying activity than wheat flour, with values of approximately 14.2-15.8 compared with 4.18 for wheat flour. Oscillatory rheology indicated a stronger elastic response in soaked-bean systems than in boiled-bean systems. This tendency was consistent with the pasting profiles. Boiled-bean flour showed the lowest final viscosity, 632.75 mPa·s, while wheat flour and the wheat-soaked bean blend maintained much higher values, 2388.75 and 2282.50 mPa·s, respectively.

Conclusions: Bean pre-treatment strongly shaped the functional and rheological-pasting behaviour of wheat-bean flour systems. Soaked-bean flour promoted stronger structure formation and maintained paste-building capacity in blends, whereas boiled-bean flour markedly reduced final viscosity. These differences show that wheat-bean systems can be tailored by selecting the bean-flour variant according to the desired colour, interfacial functionality and viscosity profile.