Gluten Network Research Articles

Ultrasound-assisted separation of wheat flour: Enhancing the degree of separation and characterization analysis

A novel ultrasound-assisted separation (UAS) method was proposed to enhance the efficiency of gluten starch and wheat separation. Factor experiments were conducted to optimize UAS conditions. The results showed that the highest yield of gluten and starch was obtained under probe-type ultrasonic power, temperature, and time of 500 W, 35 °C, and 15 min, respectively. Compared to non-ultrasonic separation, dry basis yield and purity of gluten increased by 0.56% and 10.96%, while A-starch yield and purity increased by 21.75% and 5.56%. Additionally, UAS improved the color and the concentration of particle size distribution for gluten and starch. UAS did not affect gluten molecular weight and disrupt starch structure, but resulted in a denser structure of gluten network and caused more starch particles to be exposed. The viscoelasticity of gluten and starch separately increased and reduced with UAS, implying ultrasound aids in the dispersion of both starch and proteins.

Effects of Commercial Yeast on the Quality of Frozen Dough and Steamed Bread in Different Regions of China

This study delved into the impact of various commercial yeast strains from different geographic regions on the quality attributes of dough and steamed bread. The investigation encompassed aspects such as fermentation dynamics, texture profiles, and overall quality features of frozen dough and steamed bread products. Eighteen distinct commercial yeast strains were utilized to prepare dough samples. The findings revealed minimal disparity in the color and height-to-diameter ratio of the resulting steamed bread across all samples. However, frozen doughs formulated with commercial yeast sourced from the southern regions of China exhibited enhanced CO2 production, heightened freezing resilience, a more pronounced gluten network structure, increased flexibility, and reduced presence of weakly bound water that contributes to ice crystal formation within the dough matrix. Each yeast strain exhibited a CO2 production volume exceeding 900 mL. Notably, the strains sourced from the southern region of China displayed the most superior freeze-tolerance rate (mean 0.84), surpassing those originating from central China (0.81) and northern China (0.74). Textural analyses unveiled that frozen dough steamed bread produced with yeast strains from the northern region exhibited diminished pliability and chewiness. This comprehensive study serves as a valuable resource for the judicious selection of commercial yeast strains in the realm of industrial frozen dough and steamed bread production.

Effects of ferulic acid on the polymerization behavior of gluten protein and its components

The effects of ferulic acid (FA) at different concentrations on the aggregation behaviors of gluten and its components (gliadin and glutenin) were determined in this study. Results showed that the free sulfhydryl content of glutenin and gluten significantly reduced while the mean particle size of gluten increased following FA supplementation (0.5%). Moreover, β-sheet content of gluten increased by 20.40% compared with the control group when 0.5% FA was added. Contrarily, higher concentrations (1.0 and 1.5%) of FA significantly reduced tyrosine (TYR) bimodal ratio of glutenin. Furthermore, the concentrations increased the polarity of tryptophan (TRP) residues microenvironment, which promoted the formation of a disordered gluten structure. Additionally, SDS-PAGE showed that 0.5% FA supplementation promoted the formation of high molecular weight gluten by cross-linking and aggregation of low molecular weight gluten components. Using atomic force microscopy, it was confirmed that at 0.5% FA promoted the cross-linking aggregation of gluten molecules. Further, the microscopy analysis showed that higher doses of FA contributed to an uneven distribution of gluten aggregates and a disordered and loose structure of gluten network, which was not favorable for the formation of continuous and stable dough.

Effect of sweet potato flour on pasting, aggregation properties and dough quality of wheat flour

Sweet potato flour (SPF), as a functional substitute for wheat flour (WF), has gained popularity among consumers in the development of nutritious food products. However, the mechanism of SPF on gluten in dough remains unclear. Effects of SPF on the pasting characteristics, gluten aggregation properties, and the quality of dough were investigated. The results showed that SPF-WF exhibited low pasting properties, and pasting temperature increased by 22.35%–26.98%. SPF-WFs were lower in peak viscosity (62.57%–88.17%), trough viscosity (80.32%–96.67%), breakdown viscosity (11.58%–66.37%), final viscosity (70.72%–96.95%), setback viscosity (57.83%–97.33%), and peak time (16.26%–29.30%). Compared with WF dough, SPF-WF dough had higher hardness and lower elasticity. Microstructure images showed that SPF changed the pore size of the gluten network and caused starch to accumulate. SPF could accelerate gluten aggregation, decrease gluten network strength, and reduce aggregation energy, possibly due to the increase of disulfide bonds from 1.12% to 12.52% (P < 0.05). Moreover, SPF mediated medium molecular weight gluten as well as monomer gluten were polymerized into large molecular weights. In summary, SPF might mediate gluten aggregation and 10% substitution of SPF showed a significant level compared to others.

The resting process: a comprehensive review of the effects on dough properties and resulting noodles quality, including improvement strategies

SummaryThe production processes of different types of noodles are slightly different, but the main production process includes kneading, resting, rolling, sheeting and cutting. Among them, resting is an important step in noodle‐making that has a major impact on the final quality of the noodles. After the kneading is over, the dough needs to rest for a period of time before it can be pressed into sheets. The effectiveness of the dough resting process led to a more uniform and compact gluten network distribution and improved the texture and cooking properties of the noodles compared to those without resting. From the literature reviewed, reasonable dough resting times, temperatures and humidity can improve the quality of the finished product. This review aims to summarise the concept of the dough resting process and factors affecting dough resting, discuss the effect of the resting process on dough properties and noodle quality, and suggest specific improvement strategies.

Dynamic behavior of zein-gluten interaction during extruded noodle processing

The impact of adding zein on the gluten network during extruded noodle processing and the quality of the noodles by extrusion-cooking were investigated. These changes were studied by size exclusion-high performance liquid chromatography (SE-HPLC), free sulfhydryl (SH) measurement, non-covalent interactions, Fourier-transform infrared spectroscopy (FTIR), particle size analysis, confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM). Zein reduced the protein aggregation, resulting in a higher free sulfhydryl content and increased hydrogen bonds and hydrophobic interactions during noodle processing. Moreover, Zein reduced the relative content of β-sheets by 4.54% and 7.48% at the extrusion and cooking stages, respectively. Zein decreased the particle size during extrusion but increased it during cooking. Zein improved the compactness and strength of noodle microstructure during cooking, exhibited higher hardness and impeded water mobility compared to extruded noodles made only with wheat flour (WF). The extruded noodles containing zein showed a significant increase of 26.10% and 61.11% in tensile strength and distance, respectively. Zein did not cause significant changes in the cooking loss and water absorption in the extruded noodles. Research on the impact of zein on protein during the processing of extruded noodles could provide a dependable approach and valuable mechanistic insights for improving the quality of extruded noodles.

Effect of salt and kansui on rheology, water mobility and physicochemical properties of long-chain inulin non-fermented dough and its noodles quality

Salt and kansui are usually added to flour to enhance the quality of flour products. However, the technical roles in long-chain inulin (FXL) dough formation are not well understood. The physicochemical properties and texture changes of FXL dough and noodles after adding salt and kansui were studied. The data revealed that the salt and kansui increased the G′, and G″, disulfide bond content, and the β-sheet content of the FXL dough. SEM results showed that low salt and kansui contents had different effects on the gluten network, especially 1% kansui, which had the best effect on the gluten network structure. Samples supplemented with 1.5% kansui significantly increased hardness and cooking loss (p < 0.05), with values of 84.53 N and 5.48%, respectively. Salt and kansui increased the crystallinity of starch measured by XRD. Therefore, adding salt and kansui may be a feasible approach to alleviate fibre enriched flour products.

Structural characteristics variations of dough incorporated with long-chain inulin modified by phosphorylation

In the study, long-chain inulin (FXL) was modified by phosphorylation (PFXL) to obtain new characteristics for improving the quality of dough. The secondary structure, disulfide bond content, surface hydrophobicity, and microstructure of gluten in dough, as well as the emulsification properties of gluten, were investigated. The results showed that the PFXL could affect the gluten structure through hydrogen bonding interactions and hydrophobic interactions, thus increasing the contents of β-sheets structure, α-helices structure and the disulfide bond, and decreasing the surface hydrophobicity of the dough. And the emulsification activity and stability of gluten were also improved. A more stable and ordered gluten network structure was promoted to form mainly through a liquid lamellar film formed by PFXL. Generally, the phosphorylation modification for FXL is an effective alternative to increasing the additive amount of dietary fiber in the dough and improving its quality.

Evaluation of the effects of thermal processing on antioxidant activity and digestibility of green tea noodles: Based on polyphenol stability and starch structure

The health benefits of green tea noodles (GTN) are strongly influenced by polyphenols' thermal stability and starch's thermal denaturation. This study aimed to comprehensively assess the influence of different thermal processing methods (i.e., steaming, boiling, roasting and frying) on the antioxidant activity and in vitro starch digestibility of GTN. As a result of thermal processing, the polyphenol content and antioxidant activity decreased, with correlation analysis showing a significant increase in polyphenol retention as antioxidant activity increased. GTN showed the greatest polyphenol stability during steaming compared with other thermal processing. Under the optimal cooking time, steaming and frying processing methods remarkably delayed the starch hydrolysis rate and reduced the estimated glycemic index (eGI). Further analysis proved that polyphenol content and retention rate, starch structure and the state of starch in the gluten network directly affected the in vitro starch digestion properties of GTN. Thus, steam processing will be an effective method for maximizing the functional properties of GTN from a healthy perspective.

Whole wheat flour replaced by sprouted wheat improves phenolic compounds profile, rheological and bread-making properties

This study investigated the effect of whole wheat flour partially replaced by sprouted whole wheat flour on phenolic profile, dough rheological properties and bread characteristics. A 3 × 3 factorial design was used to evaluate three sprouting times (24, 48 and 72 h) and three replacement percentages (5, 15 and 25%) compared to the control sample (whole wheat flour). Total amylolytic activity (+43%), α-amylase (+73%) and antioxidant activity (+3.8 times higher) of flours progressively increased with sprouting times. However, it did not change the total phenolic content. The progressive increase of sprouting time and replacement levels can negatively impact the dough and bread-making due to a weakened gluten network and reduced dough strength caused by the increased enzymatic action. Moreover, bread firmness and chewiness were significantly increased. Eighty-eight phenolic compounds were annotated by metabolomics tools. Phenolic acids had the highest ion abundance due to the isomers of ferulic acid. Principal Components Analysis showed great variability of phenolic compounds abundance in sprouting time (99%) and replaced flours (87%). These results suggest that sprouted wheat flours can be incorporated into baked products, although improving the bread characteristics is highly dependent on the sprouting time and its replacement levels.

The Effect of Freeze-Thaw Cycles on the Microscopic Properties of Dumpling Wrappers.

Dumplings are a traditional Chinese food welcomed by Chinese people. Research has indicated that process of quick-frozen wheat cultivars and their gliadins are all related to the quality and shelf-life of dumplings. Therefore, the effect of freeze-thaw cycles on the textural properties and microscopic characteristics of two types of quick-frozen dumpling wrappers (Zhaomai and Wenmai 19) and conformation of their gliadins were investigated. Scanning electron microscopy showed that Wenmai 19 dumpling wrappers had apparent damage after the first cycle, but Zhaomai wrappers did not reveal significant changes until the fourth cycle. The particle size distribution in the starch granules of Wenmai 19 wrappers varied in terms of mechanical damage, but Zhaomai delayed or avoided such effects. FT-IR found a loose protein structure of the gliadins. Differential scanning calorimetry showed that gliadins of Wenmai 19 degenerated more than those of Zhaomai. The crosslinking of gliadin and glutenin maintained a high-quality gluten network, thus protecting the gliadin stability from ice crystals. In turn, the gliadin maintained the strength of the gluten network. Therefore, raw flours with high-quality protein networks are more suitable for frozen dumplings. Freeze-thaw cycles dramatically decreased the textural characteristics of dumpling wrappers and the microscopic characteristics of their gliadin proteins. Concerning wheat cultivars with weak gluten, flours with high-quality protein networks are more suitable as raw materials for frozen dumplings.

Effect of sheeting stress and heating on the molecular chain structure, size, and conformation of gluten proteins during noodle processing

In this paper, the changes in molecular structure, size distribution, and conformation of gluten induced by the mechanical stress during sheeting and the heating effect during cooking of noodles were investigated by atomic force microscopy (AFM), X-ray scattering (SAXS), and size-exclusion chromatography multi-angle laser light scattering (SEC-MALLS). AFM results showed that the height and width of gluten molecular chains were decreased after calendering and increased post-cooking. Calendering reduced the molecular size and compacted the gluten network (increased Dm). The SDS extractable gluten components showed a quasi-spherical chain conformation but gradually changed to a random coil conformation due to heating. According to SEC-MALLS profiles, calendering and appropriate heating (4 min) promoted the homogeneity of molecular mass of glutenin polymer. The mechanical depolymerization and the heat-promoted polymerization of gluten could be due to the breakage and formation of disulfide bonds and the interconversion of sulfhydryl groups.

Effects of Wheat Flour Substitution with High‐Amylose Corn Flour on the Quality of Dough and Chinese Steamed Bread

AbstractIn order to increase the nutritional value of Chinese steamed bread (CSB), high‐amylose corn flour (HACF) is used to partially replace wheat flour (WF) in the preparation of CSB. In CSB prepared with 0–50% HACF, the study examines the thermomechanical characteristics of the dough, starch–gluten network, quality, and in vitro digestibility. According to Mixolab data, the addition of HACF reduces dough stability and increases the thermal stability of pasting. In doughs with HACF concentrations &gt;30%, scanning electron microscopy observations reveal that the starch–gluten connections are weaker and the network structure is discontinuous. The addition of HACF reduces the specific volume and increases the hardness, gumminess, and chewiness of the CSB. Compared with the WF‐CSB, the content of resistant starch increases from 12.01% to 28.49% in the HACF‐CSB, whereas there is a reduction in the glycemic index from 94.39 to 57.55. In summary, the addition of 30% HACF can increase the resistance of CSB and enhance its nutritional value without unduly reducing the desirable organoleptic qualities.

Effect of sodium carbonate on the properties of seventy percent of Tartary buckwheat composite flour-based doughs and noodles and the underlying mechanism.

The impact of Na2 CO3 on the properties of doughs and noodles containing 70% Tartary buckwheat flour was investigated. Low-field 1 H nuclear magnetic resonance showed the mobility of water in the doughs significantly declined with the addition content of alkali from 0% to 0.9%. Na2 CO3 promoted the transformation from free sulfhydryl groups to disulfide bonds in doughs because the sulfhydryl groups in cysteine preferred to form thiolate anion and then oxidate under alkaline conditions. As for non-covalent chemical interactions, a significant increase of hydrogen bonds and a decrease of hydrophobic interactions were observed after Na2 CO3 addition. Quantitative analysis of microstructure showed that more uniform and denser gluten networks with higher branching rate and shorter average protein length and width formed in the doughs with 0.3%-0.6% of Na2 CO3 . The aggregated glutenin macropolymer and enhanced protein structure led to significantly stronger tensile of Tartary buckwheat dough sheets, which could meet the demand of continuous processing in the factory. Dough with alkali had higher swelling power and pasting viscosities, contributing to higher water absorption, and improved textural attributes of cooked noodles. This study demonstrated the possibility of adding Na2 CO3 at a moderate level for promoting the sheeting, cooking, and eating properties of high Tartary buckwheat flour composite noodles.

Radio frequency disinfestation of Tribolium castaneum (Herbst) in semolina: An emerging thermal technique

AbstractTribolium castaneum (Herbst) infestation is inevitable during the storage of semolina and its derivative products. This study applied the emerging radio frequency (RF) heating technology to disinfest T. castaneum in semolina, using a 40.68 MHz, 10 kW RF unit. In the context of considering the quality of semolina, .8 A RF current load with 8 min exposure time was found to be optimum and effective for attaining 100% disinfestation of T. castaneum in semolina. Changes in moisture content, color and gluten content were determined in RF treated semolina to evaluate the effect of RF heating. Mortality of all life stages of T. castaneum was 100% at 64.40 ± 1.40°C of semolina during RF heating. The susceptibility of T. castaneum to RF heating was egg &gt; pupa &gt; larva &gt; adult. Gluten variance was minor, confirmed by SEM micrographs showing slight differences in structure compared to untreated semolina. This supports RF as an eco‐friendly method for semolina disinfestation, making it a promising innovation.Practical ApplicationsThis study applied RF disinfestation method for T. castaneum in semolina, research findings in the study indicates that RF treatment for disinfestation of T. castaneum obtained a good result with 100% mortality. The RF treated semolina had a less color variance, significant moisture reduction, compared to control and slight difference in gluten network and starch molecule structure of RF treated semolina compared to untreated semolina.

Precooking treatments affect the sensory and tensile properties of autoclaved recooked noodles via moisture distribution and protein structure.

To improve the quality of autoclaved recooked noodles (ARNs), this study explored the effects of precooking on the sensory and tensile properties of ARNs from the perspectives of changes in protein structure and water distribution. The results showed that the ARNs of two kinds of pretreatments (Boiling 2min, Boiling 1min+Steaming 2min) presented the best sensory quality (average score≥7.50) and high tensile properties (tensile distance≥45.24mm). After autoclaving and recooking, the proportion of tightly bound water increased by 11.30%-12.52%, resulting in stronger water-solid interaction. The results of laser confocal microscopy (CLSM) proved that a strengthened gluten network (protein percentage area≥40.28%; junction density≥10.96×10-4) appeared. Therefore, appropriate precooking treatment could effectively improve the sensory quality and tensile properties of ARNs by enhancing the tightly bound water ratio and strengthening the gluten network.

Investigation of the cryoprotective mechanisms of silver carp muscle hydrolysate for frozen dough exposed to multiple freeze-thaw cycles

This study aimed to elucidate the cryoprotective mechanisms associated with silver carp muscle hydrolysate (SCMH) in the context of frozen dough subjected to 0–6 freeze-thaw (FT) cycles. The presence of SCMH in the frozen dough matrix effectively mitigated the reduction in yeast viability, as evidenced by a mere 3.7% decrease in OD660 compared to a 7.6% decline observed in the control group after 6 FT cycles. Furthermore, the incorporation of SCMH exhibited a progressive increase in the concentration of numerous free amino acids (e.g., Threonine, Alanine, Leucine, and Lysine) throughout the FT cycles. Additionally, the introduction of SCMH into the dough formulation yielded multiple benefits. It substantially curtailed water loss and hindered the shift of water from T21 to T22 during FT cycles. Moreover, it exerted an inhibitory effect on the growth of ice crystals, as indicated by a 49% reduction in the average ice crystal area following 6 FT cycles. This multifaceted cryoprotective action contributed to a subsequent decrease in cryodamage to the dough matrix, gluten network structure, and yeast cells. In summary, these findings underscore the considerable potential of integrating SCMH as a cryoprotective agent to enhance the overall quality of frozen dough products.

Multiphoton microscopy is a nondestructive label-free approach to investigate the 3D structure of gas cell walls in bread dough

During the different steps of bread-making, changes in the microstructure of the dough, particularly in the gas cell walls (GCW), have a major influence on the final bread crumb texture. Investigation of the spatial conformation of GCWs is still a challenge because it requires both high resolutions and 3D depth imaging. The originality of the present work lies in the use of label-free non-destructive multiphoton microscopy (NLOM) to image the 3D structure of GCWs, shedding light on their behavior and organization in wheat bread dough. We demonstrated that second and third harmonic generation (SHG, THG) allow imaging, respectively, of starch granules and interfaces in bread dough, while the gluten matrix was detected via two-photon excitation fluorescence (TPEF). Last, a distinction between the gluten network and starch granules was achieved using gluten endogenous fluorescence (EF) imaging, while the position, size, and 3D orientation of starch granules in GCWs were determined from harmonic imaging, made possible by the acquisition of backward and forward SHG with linear polarization. These innovative experiments highlight the strengths of NLOM for a label-free characterization of bread dough microstructure for the first time, in order to understand the role of starch granules in dough stabilization.

Unravelling the relationships between wheat dough extensional properties, gluten network and water distribution

Wheat flour doughs were prepared from four commercial wheat flours at different mixing times and hydration levels in order to obtain variations in their rheological properties and gluten network structure. Their rheological behavior was assessed by Dynamic Mechanical Analysis (DMA) for their viscoelastic properties and by Lubricated Squeezing Flow (LSF) for their extensional properties. Gluten network structure was determined by quantitative analysis of confocal microscopy (CLSM) images. Among the rheological properties, the consistency index (k) derived from the extensional viscosity and the elastic modulus ratio (E′Max/E′Min) varied between 10 and 42 kPa.sn, and 4 and 26, respectively. They were found to be consistently linked to the gluten network structure. This structure was primarily described by the morphological descriptor, “protein width”, which defines the thickness of protein strands, the average value of which varied between 1.7 and 2.5 μm. Both rheological properties and morphological criteria were significantly influenced by dough hydration rather than by mixing time, whereas the flour characteristics did not play a major role. Interpretation of these results, supported by previous 1H time domain nuclear magnetic resonance (TD-NMR) results concerning water distribution profiles, showed that an optimal dough is defined by a high dough consistency index (k) and a highly cross-linked gluten network (low E'Max/E'Min ratio), presenting thin protein strands.

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.