Wheat dough imitating artificial dough system based on hydrocolloids and glass beads

Effects of sugar beet pectin on the pasting, rheological, thermal, and microstructural properties of wheat starch

The effects of addition of sugar beet pectin (SBP) on the pasting, rheological, thermal, and microstructural properties of wheat starch (WS) were investigated. Results revealed that SBP addition significantly increased the peak viscosity, trough viscosity, breakdown value, final viscosity, and setback value of WS, whereas decreased the pasting temperature. SBP raised the swelling power (from 13.44 to 21.32 g/g) and endothermic enthalpy (ΔH, from 8.17 to 8.98 J/g), but decreased the transparency (from 9.70 % to 1.37 %). Regarding rheological properties, WS-SBP mixtures exhibited a pseudo-plastic behavior, and SBP enhanced the viscoelasticity, but decreased the deformability. Particle size distribution analysis confirmed that SBP promoted the swelling of WS granules. Fourier-transform infrared spectroscopy results suggested that the interactions between SBP and WS did not involve covalent bonding, and the formation of ordered structure was inhibited by SBP addition. Additionally, scanning electron microscopy observation found that the gel network of WS-SBP mixtures became more irregular, pore size gradually decreased, and the wall became thinner as the SBP concentration increased. These results indicated that SBP is a promising non-starch polysaccharide that can enhance the processing properties of WS.

Microscopic analysis of gluten network development under shear load-combining confocal laser scanning microscopy with rheometry

A comprehensive in-situ analysis of the developing gluten network during kneading is still a gap in cereal science. With an in-line microscale shear kneading and measuring setup in a conventional rheometer, a first step was taken in previous works toward fully comprehensible gluten network development evaluation. In this work, this setup was extended by an in-situ optical analysis of the evolving gluten network. By connecting a laser scanning microscope with a conventional rheometer, the evaluation of the rheological and optical protein network evolution was possible. An image processing tool for analyzing the protein network was applied for evaluating the gluten network development in a wheat dough during the shear kneading process. This network evaluation was possible without interruption or invasive sample transfer comparing it to former approaches. The shear kneading system was able to produce a fully developed dough matrix within 125% of the reference dough development time in a classical kneader. The calculated network connectivity values from frequency testing ranged over all samples was in good agreement with traditional kneaded wheat dough just over peak consistency.

Micro-Scale Shear Kneading-Gluten Network Development under Multiple Stress-Relaxation Steps and Evaluation via Multiwave Rheology

To evaluate the kneading process of wheat flour dough, the state of the art is a subsequent and static measuring step on kneaded dough samples. In this study, an in-line measurement setup was set up in a rheometer based on previously validated shear kneading processes. With this approach, the challenge of sample transfer between the kneader and a measurement device was overcome. With the developed approach, an analysis of the dynamic development of the dough is possible. Through consecutive stress–relaxation steps with increasing deformation, a kneading setup in a conventional rheometer is implemented. Fitting of the shear stress curve with a linearization approach, as well as fitting of the relaxation modulus after each kneading step, is a new way to evaluate the matrix development. Subsequently, multiwave rheology is used to validate the kneading process in-line. The shear kneading setup was capable of producing an optimally developed dough matrix close to the reference kneading time of 150 ± 7.9 s (n = 3). The linearization approach as well as the power-law fit of the relaxation modulus revealed gluten network development comparable to the reference dough. With this approach, a deeper insight into gluten network development and crosslinking processes during wheat flour dough kneading is given.

Impact of the particle-polymer interface on small- and large-scale deformation response in protein- and carbohydrate-based food matrices

Interfaces are important regarding the mechanical behavior of foods. In particle-polymer-based food systems, the rheological effect of interface characteristics between microscopic particles and viscoelastic polymers is controversial. By using a new approach of presenting defined glass beads surfaces, which imitate functional groups of starch particle surfaces, the adhesiveness and the adsorption mechanism between particle and polymeric food matrix (protein-/carbohydrate-based) can be controlled. The combination of defined particle-polymer interfaces with a comprehensive rheological analysis gives new insights into the effect of particle-polymer interfaces on the mechanical properties of food. Independent of the matrix-type, non-adhesive particles show the strongest network at low stress (protein-based: network strength A_f = 2.02 ± 0.16 ∗ 10⁴ Pas^1/z), but the fastest network breakdown under higher stress (fracture strain protein-based 4.40 ± 0.08). Adhesive particles behave inverse (A_f = 1.02 ± 0.24 *10⁴ Pas^1/z; fracture strain 5.38 ± 0.32). Consequently, particle supplemented protein-/carbohydrate-based matrices have properties similar to particle reinforced rubbers and exhibit a more or less pronounced Payne effect depending on the adhesiveness. Besides the adhesiveness, the adsorption mechanism affects the deformation behavior of particle-polymer based system. The highly adhesive but unspecific adsorption of carbohydrate-based polymers at cyano-functionalized surfaces shows a similar relaxation behavior as non-adhesive surface functionalization.

Thermally induced gluten modification observed with rheology and spectroscopies

The protein vital gluten is mainly used for food while interest for non-food applications, like biodegradable materials, increases. In general, the structure and functionality of proteins is highly dependent on thermal treatments during production or modification. This study presents conformational changes and corresponding rheological effects of vital wheat gluten depending on temperature. Dry samples analyzed by X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR) and thermalgravimetric analysis coupled with mass spectrometry (TGA-MS) show surface compositions and conformational changes from 25 to 250 °C. Above 170 °C, XPS reveals a decreased N content at the surface while FTIR band characteristics for β-sheets prove structural changes. At 250 °C, protein denaturation accompanied by a significant mass loss due to dehydration and decarbonylation reactions is observed. Oscillatory measurements of optimally hydrated vital gluten describing network properties of the material show two structural changes along a temperature ramp from 25 to 90 °C: at 56-64 °C, the temperature necessary to trigger structural changes increases with the ratio of gliadin to total protein mass, determined by reversed-phase high performance liquid chromatography (RP-HPLC). At a temperature of 79-81 °C, complete protein denaturation occurs. FTIR confirms the denaturation process by showing band shifts with both temperature steps.

Characterizing the impact of starch and gluten-induced alterations on gelatinization behavior of physically modified model dough

Gelatinization properties of physically modified starch-gluten matrices are often exclusively traced back to starch constitution without considering the state of gluten. Thus, gelatinization of model dough, combining reference (rS)/modified starch (mS) with reference (rG)/modified gluten (mG), was investigated using nuclear magnetic resonance and differential scanning calorimetry to relate structural alterations of biopolymers to their hydration properties. No differences were found in gelatinization onsets of model dough consisting of rS and mS combined with mG (starch: gluten = 50:50 (m/m)), although gelatinization enthalpy of mS mG (1.7 ± 0.4 J/g dm) was significantly lowered in comparison to rS mG (2.2 ± 0.2 J/g dm). Relaxation time T₂ was significantly reduced for mG in comparison to rG, demonstrating a tighter water binding of mG. This suggests that reduced gelatinization enthalpy of modified starch-gluten matrices is caused by a destruction of crystal parts of modified starch and by a tighter water binding of modified gluten.