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Project

The Flow of Mixed-cereal Dough - Exploring the Rheology of Bread Dough Made with Blends of Wheat (Triticum aestivum L.) and Rye (Secale cereale L.) Flour

This PhD research delves into the complex world of mixed-cereal bread dough rheology, and more specific that of blended wheat flour-rye flour dough.

In wheat flour (WF) bread making a key determinant for the final bread quality is known to be the gluten network. This 3D network provides wheat flour dough with the necessary viscoelastic properties that allow to produce voluminous breads with a uniform crumb structure. Recent changes in consumers’ interests towards nutrient-dense foods have increased the popularity of non-wheat grains.

Doughs prepared from these non-wheat grains, however, do not possess the same ability as wheat to develop a strong gluten network, and consequently have different rheological properties resulting in a different final bread structure. Therefore, in order to produce bread doughs with the necessary rheological properties to obtain final breads of high quality that satisfy market demand, a strong understanding of the rheological properties of mixed-cereal bread dough and its various constituents is required.

A possibly fruitful strategy to produce bread of high quality with a high nutritional value is the blending of WF and a non-WF. For the latter rye flour (RF) was chosen in this PhD research. To this end, an elaborate study of the rheological properties of blended WF - RF doughs was performed. While linear dynamic measurements are routinely used to describe dough rheology, it were mainly the uniaxial extensional measurements that displayed significant potential. RF components appear to play a major role in the rheology of WF – RF doughs. It was hypothesized that especially arabinoxylan (AX) and protein play a key role in the rheology of blended WF - RF bread dough.

The impact of AX on dough rheology was investigated via an enzymatic approach using xylanases from Aspergillus aculeatus and Bacillus subtilis. Gas chromatography was used to characterize the AX population. The role of proteins in the rheology of doughs prepared from WF-RF blends was examined using redox agents. Potassium iodate, a strong oxidant, was used to increase the number of disulfide (SS) bonds in dough. L-cysteine, a commonly used reductant in the bread industry, decreased the amount of SS bonds. High-performance liquid chromatography (HPLC) and measurements of the amount of free sulfhydryl groups were used to characterize the protein fractions and assess the effects of the redox agents. The impact of both AX and proteins on dough rheology was investigated via uniaxial extensional and small-amplitude oscillatory shear measurements.

Finally, the use of constitutive equations to model dough extensional rheology was tackled. Dough is a complex multiscale material, which typically requires a substantial set of fitting parameters to describe its rheological behavior using the classical set of mechanical models. Instead, this PhD research focused on the use of a Fractional K-BKZ framework to model dough rheology with a limited number of parameters. In essence, this model combines the input of the linear fractional Maxwell model with a damping function in the non-linear K-BKZ framework. For the first time, the damping function was determined via stress relaxation measurements in extension.

Rheology serves as a powerful tool to investigate bread dough and can aid in the development of high-quality multigrain breads. This PhD research focused on a select number of constituents in blended WF-RF doughs, but the methodology and techniques can be extended to other types of constituents (starch, β-glucans, proteins other than wheat gluten and rye secalins, etc.) or multigrain systems as well. The fractional K-BKZ framework, that can accurately model dough uniaxial extensional behavior, is a next step towards an improved control of the bread making process.

Date:1 Sep 2016 →  23 Aug 2023
Keywords:rheology, bread dough, flour
Disciplines:Process engineering, Polymeric materials, Catalysis and reacting systems engineering, Chemical product design and formulation, General chemical and biochemical engineering, Separation and membrane technologies, Transport phenomena, Other (bio)chemical engineering, Condensed matter physics and nanophysics
Project type:PhD project