Structural, thermal and rheological properties of gluten dough: Comparative changes by dextran, weak acidification and their combination

Mechanism of structural and functional changes of matcha bread dough during freezing storage

This study aimed to investigate the effects of freezing duration and matcha concentration on the rheological properties, moisture distribution, and multiscale structure of dough. The results indicated that both freezing and high concentrations of matcha (≥1 %) significantly reduced the stiffness of the dough matrix, restricted its ability to expand during fermentation, and disrupted the structure of gluten protein. Furthermore, freezing induced moisture redistribution within the dough. Specifically, the water content in the 0 % matcha dough decreased by 1.5 %, indicating a weakening of protein-moisture interactions, disruption of disulfide bond conformations, and inhibition of disulfide bond aggregation in gluten proteins, thereby destabilizing the gluten network. Additionally, freezing negatively impacted yeast gas production capability, while matcha addition did not influence yeast activity. Moreover, low concentrations of matcha did not significantly impact the multiscale structure of the dough. This study provided crucial scientific insights for recipe optimization and quality control in bread production.

Mechanism underlying the effect of soluble oat β-glucan and tea polyphenols on wheat gluten aggregation characteristics

The mechanism of how the coexistence of oat β-glucan (OβG) and tea polyphenols (TP) impacts gluten aggregation properties was investigated. The OβG might form interchain hydrogen bondings and compete for water with gluten, which could increase gluten aggregation and the gluten network's expansion, leading to its increasing average particle size (by 17.23 %) with 5%OβG. The physicochemical characteristics of TP and OβG + TP groups showed similar changing trends, indicating the predominant effect of TP; however, the effect was, to some extent, enhanced with the presence of OβG. This might be because OβG induced a more expanded network of gluten, favoring the access and attack of TP to unfold or disrupt the gluten structure by breaking disulfide bonds, as confirmed by the red-shifts in fluorogram, increasing content of free sulfhydryl by 250 % (without OβG) and 312 % (with OβG), and decreasing particle size of gluten by 10.43 % (without OβG) and 21.08 % (with OβG) when the addition of TP was 2 %. Moreover, with the increasing of TP, the tremendous unfolding or disrupting gluten structure exposed more amino acids whereas decreased the intermolecular contacts and extended chains of gluten, consequently leading to the increasing hydrogen bonds and hydrophobic interactions while reducing the content of β-sheets, respectively.

Wheat gliadin/xanthan gum intermolecular complexes: Interaction mechanism and structural characterization

In this study, the interactions between wheat gliadin (GL) and xanthan gum (XG) were investigated to design new systems with potential applications as a gluten-free substitute product. Combining spectral with morphological and molecular docking methods allowed the establishment of the complexation mechanism between globular hydrophobic GL and the hydrophilic XG with an extended and partially disordered backbone. GL maintains intact its hydrophobic core even at high GL/XG ratios and organizes into small aggregate-type assemblies. The stable and uniform complexes have a low GL content, based on intermolecular hydrogen bonds and hydrophobic interactions. The GL/XG combining ratio influences the size, structure and interaction mechanism of the microparticles. The preferred sites of interaction and the binding affinities were determined by molecular docking on GL libraries and XG models. This research may provide significant knowledge for the development of low-GL wheat food products using a dietary fiber polysaccharide as a functional compound.

Enhancing bread anti-staling with glucose-derived Maillard reaction products: In-depth analysis of starches, gluten networks, and moisture status

In this study, six types of amino acids (Ala, Phe, Glu, Gly, Ser, and Lys) were combined with glucose to produce Maillard reaction products (MRPs) named G-Ala, G-Phe, G-Glu, G-Gly, G-Ser and G-Lys. The effect of MRPs on bread staling was evaluated through texture and sensory analyses during storage. Furthermore, the study comprehensively analyzed the anti-staling mechanisms of MRPs by examining moisture content, starches, and gluten network changes. The results indicated that G-Gly and G-Glu delayed bread staling, with G-Gly showing the most significant effect. Compared with control, the staling rate and starch crystallinity of G-Gly bread decreased by 24.07% and 7.70%, respectively. Moreover, G-Gly increased the moisture content (3.48%), weakly bound water mobility (0.77%), and α-helix content (1.00%) of bread. Component identification and partial least squares regression further confirmed the aldonic acid, heterocyclic acids and heterocyclic ketones in MRPs inhibit water evaporation, gluten network loosening, and starch degradation, thereby delaying bread staling.

Effects of konjac glucomannan with different degrees of deacetylation on the properties and structure of wheat gluten protein

The properties and structure of gluten protein with different deacetylation degrees of konjac glucomannan (KGM) were investigated, in an attempt to improve the quality of gluten protein in flour products. Results showed that deacetylated KGM (DKGM) could improve the textural properties and enhance the thermal stability of gluten protein. DKGM increased the water holding capacity and shortened the T2 relaxation time of gluten after removing some acetyl groups. As the deacetylation degree increased, the hardness and adhesiveness of gluten gels gradually increased, while the springiness decreased. In addition, the presence of DKGM promoted the conversion from free sulfhydryl to disulfide bonds and increased the β-sheet content in gluten protein. The low-deacetylation KGM decreased the surface hydrophobicity and fluorescence intensity of gluten protein, and the microstructures of gluten gels became more compact. Compared with gluten protein-KGM complex gel, the degradation temperature of gluten protein-DKGM complex gels was observed to increase by >3 °C. Overall, the low-deacetylation KGM was beneficial for improving the physicochemical properties and maintaining the network structure of gluten protein. This study provides valuable references and practical insights to improve gluten quality in the flour industry.

Effect of different molecular weight β-glucan hydrated with highland barley protein on the quality and in vitro starch digestibility of whole wheat bread

Whole wheat bread has high nutritional value, but it has inferior baking quality and high glycemic index, which needs to be improved by methods such as adding protein and β-glucan. This study investigated the effects of β-glucan and highland barley protein of different molecular weights (2 × 104, 1 × 105, and 3 × 105 Da) and different hydrate methods (pre-hydrate and not pre-hydrate) on the characteristics of whole wheat dough and bread. The mixing properties and rheological properties demonstrated that β-glucan pre-hydrated with highland barley protein were able to reduce the dough tan δ, reduce the dough viscoelasticity, while enhance the gluten network structure and dough deformation resistance. Compared to the control sample, the medium molecular weight pre-hydrate bread had a better specific volume of 3.21 mL/g, lower hardness of 527.28 g. In vitro starch digestion characteristics and ATR-FTIR showed that low and high molecular weight pre-hydrate increased the short-range ordered structure of starch and reduced the starch digestibility, while not pre-hydrated medium molecular weight hydrate had the lowest level of starch digestibility.

Improvement on wheat bread quality by in situ produced dextran-A comprehensive review from the viewpoint of starch and gluten

Deterioration of bread quality, characterized by the staling of bread crumb, the softening of bread crust and the loss of aroma, has caused a huge food waste and economic loss, which is a bottleneck restriction to the development of the breadmaking industry. Various bread improvers have been widely used to alleviate the issue. However, it is noteworthy that the sourdough technology has emerged as a pivotal factor in this regard. In sourdough, the metabolic breakdown of carbohydrates, proteins, and lipids leads to the production of exopolysaccharides, organic acids, aroma compounds, or prebiotics, which contributes to the preeminent ability of sourdough to enhance bread attributes. Moreover, sourdough exhibits a "green-label" feature, which satisfies the consumers' increasing demand for additive-free food products. In the past two decades, there has been a significant focus on sourdough with in situ produced dextran due to its exceptional performance. In this review, the behaviors of bread crucial compositions (i.e., starch and gluten) during dough mixing, proofing, baking and bread storing, as well as alterations induced by the acidic environment and the presence of dextran are systemically summarized. From the viewpoint of starch and gluten, results obtained confirm the synergistic amelioration on bread quality by the coadministration of acidity and dextran, and also highlight the central role of acidification. This review contributes to establishing a theoretical foundation for more effectively enhancing the quality of wheat breads through the application of in situ produced dextran.

Noncovalent Conjugates of Anthocyanins to Wheat Gluten: Unraveling Their Microstructure and Physicochemical Properties

Intake of polyphenol-modified wheat products has the potential to reduce the incidence of chronic diseases. In order to determine the modification effect of polyphenols on wheat gluten protein, the effects of grape skin anthocyanin extract (GSAE, additional amounts of 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%, respectively) on the microstructure and physicochemical properties of gluten protein were investigated. The introduction of GSAE improves the maintenance of the gluten network and increases viscoelasticity, as evidenced by rheological and creep recovery tests. The tensile properties of gluten protein were at their peak when the GSAE level was 0.3%. The addition of 0.5% GSAE may raise the denaturation temperature of gluten protein by 6.48 °C-9.02 °C at different heating temperatures, considerably improving its thermal stability. Furthermore, GSAE enhanced the intermolecular hydrogen bond of gluten protein and promoted the conversion of free sulfhydryl groups to disulfide bonds. Meanwhile, the GSAE treatment may also lead to protein aggregation, and the average pore size of gluten samples decreased significantly and the structure became denser, indicating that GSAE improved the stability of the gluten spatial network. The positive effects of GSAE on gluten protein properties suggest the potential of GSAE as a quality enhancer for wheat products.

Leuconostoc citreum: A Promising Sourdough Fermenting Starter for Low-Sugar-Content Baked Goods

This review highlights Leuconostoc citreum's promising possibilities as a proficient mannitol producer and its potential implications for sugar reduction, with a focus on its use in sourdough-based baked good products. Mannitol, a naturally occurring sugar alcohol, has gained popularity in food items due to its low calorie content and unique beneficial qualities. This study summarizes recent research findings and investigates the metabolic pathways and culture conditions that favor increased mannitol production by Leuconostoc citreum. Furthermore, it investigates the several applications of mannitol in baked goods, such as its function in increasing texture, flavor and shelf life while lowering the sugar content. Sourdough-based products provide an attractive niche for mannitol integration, as customer demand for healthier and reduced-sugar options increases.

Enhancement of Textural and Sensory Characteristics of Wheat Bread Using a Chickpea Sourdough Fermented with a Selected Autochthonous Microorganism

A traditional Greek sourdough, based on the fermentation of chickpea flour by an autochthonous culture, was evaluated as a wheat bread improver. The dominant indigenous microflora (Clostridium perfringens isolates) was identified by 16S rDNA analysis, and a selected strain (C. perfringens CP8) was employed to ferment chickpea flour to obtain a standardized starter culture (sourdough) for breadmaking. In accordance with toxin-typed strain identification, all isolates lacked the cpe gene; thus, there is no concern for a health hazard. Loaf-specific volumes increased with the addition of liquid, freeze-dried, and freeze-dried/maltodextrin sourdoughs compared to control bread leavened by baker's yeast only. Following storage (4 days/25 °C), the amylopectin retrogradation and crumb hardness changes (texture profile analysis) revealed a lower degree of staling for the sourdough-fortified breads. Modifications in the protein secondary structure of fortified doughs and breads were revealed by FTIR analysis. High amounts of organic acids were also found in the sourdough-supplemented breads; butyric and isobutyric acids seemed to be responsible for the characteristic 'butter-like' flavor of these products (sensory analysis). Overall, the addition of liquid or freeze-dried chickpea sourdough in wheat bread formulations can improve the specific volume, textural characteristics, and sensorial properties of loaves, along with extending bread shelf life.

Thermomechanical Stress Analysis of Hydrated Vital Gluten with Large Amplitude Oscillatory Shear Rheology

Vital gluten is increasingly researched as a non-food product for biodegradable materials. During processing, the protein network is confronted with increased thermal and mechanical stress, altering the network characteristics. With the prospect of using the protein for materials beyond food, it is important to understand the mechanical properties at various processing temperatures. To achieve this, the study investigates hydrated vital gluten under thermomechanical stress based on large amplitude oscillatory shear (LAOS) rheology. LAOS rheology was conducted at increasing shear strains (0.01-100%), various frequencies (5-20 rad/s) and temperatures of 25, 45, 55, 65, 70 and 85 °C. With elevating temperatures up to 55 °C, the linear viscoelastic moduli decrease, indicating material softening. Then, protein polymerization and the formation of new cross-links due to thermal denaturation cause more network connectivity, resulting in significantly higher elastic moduli. Beyond the linear viscoelastic regime, the strain-stiffening ratio rises disproportionately. This effect becomes even more evident at higher temperatures. Lacking a viscous contribution, the highly elastic but also stiff network shows less mechanical resilience. Additionally, at these elevated temperatures, structural changes during the protein's denaturation and network shrinkage due to water evaporation could be visualized with confocal laser scanning microscopy (CLSM).

Effect of fermentation methods on properties of dough and whole wheat bread

BACKGROUND

Whole wheat bread is high in nutritional value but poor in technological quality; therefore, research on how to improve its technological quality has attracted extensive attention. The effects of fermentation methods, including straight dough(STD), sourdough (SOD), sponge dough (SPD), and refrigerated SPD (RSD) methods, on the dough and bread quality of whole wheat bread were investigated, focusing on pasting properties, rheological properties, thermal properties, microstructure, basic quality, and starch digestibility.

RESULTS

The rapid viscosity analysis and rheological results demonstrated that SOD had the highest pasting temperature and the lowest viscosity, indicating an inhibition of starch pasting and partial protein hydrolysis, whereas the opposite trend presented by SPD and RSD indicated a greater starch hydration and a stronger gluten network. Thermal gravimetric analysis and differential scanning calorimetry results indicated reduced starch thermal degradation and increased starch pasting enthalpy in SOD and RSD. Scanning electron microscopy images revealed that the starch granules of SOD and RSD were tightly wrapped by a gluten network. SOD and RSD breads had the largest specific volume, the softest texture, and the lowest glycemic index.

CONCLUSION

The effects of different fermentation methods on dough and bread structure can provide instructive information for future studies on their applications in whole wheat bread production. © 2023 Society of Chemical Industry.

Study of Physico-Chemical Properties of Dough and Wood Oven-Baked Pizza Base: The Effect of Leavening Time

The research objective was to investigate the morpho-rheological, chemical, and structural changes of dough and Neapolitan pizza TSG as the leavening time varies and to evaluate their effects on the digestibility of starch and on the formation of acrylamide during baking. Pizza dough leavening was monitored for 48 h at 22 °C/80% RH, and the analyses were conducted at selected leavening times (0, 4, 8, 16, 24, and 48 h). It was observed that in 30 h the volume tripled and the viscoelastic dough relaxed in the first 4 h, as evidenced by the lower value of the relaxation percentage “a” and the higher rate of decay “b”, associated with a high value of the compression work, indicating the presence of a very strong gluten mesh. In the following hours, the dough lost elasticity, and in fact, the G’ modulus decreased due to the weakening of the weak interactions between the gluten proteins and the starch. This suggests that a long leavening improved the extensibility of the pizza disc, facilitating the action of the pizza maker. Thermal (TGA and DSC) and morphological (SEM) analyses evidenced the highest water removal rate from the dough, a wider starch gelatinization temperature range, a ∆H of 0.975 ± 0.013 J/g, and a more open and weak gluten structure in dough balls leavened for 16 h. As the leavening time increased, both dough and pizza base samples showed an increase in reducing sugars and free amino groups, while the rapidly digestible starch decreased in the dough following the metabolism of the yeasts and increased in the pizza base due to the starch gelatinization that occurs during baking, which makes it much more susceptible to α-amylase. Finally, the levels of acrylamide remained at the same values despite the higher availability of reducing sugars and its precursors during leavening.

Rheo-Fermentation Dough Properties, Bread-Making Quality and Aroma Characteristics of Red Bean (Vigna angularis) Sourdough Induced by LAB Weissella confusa QS813 Strain Fermentation

This study investigated the impact of in situ-formed exopolysaccharides (EPS) in red bean (Vigna angularis) sourdough fermented by Weissella confusa QS813 on dough rheo-fermentation properties, bread-making quality and aroma characteristics of red bean sourdough bread. The EPS formed in red bean sourdough and sourdough-induced acidification improved the maximum dough fermentation height, gas retention coefficient and viscoelastic properties of dough. Doughs had a lower increase rate of total SDS-soluble gluten proteins, a low decline in GMP content and similar free sulfhydryl content to wheat dough. Resultantly, breads showed declines in baking loss and hardness, increase in specific volume and lower moisture loss and staling rate after 7 days of storage. Finally, despite a reduction in the total content of aroma compounds, new aroma compounds such as acetic acid and higher contents of 3-methyl-1-butanol and 2,3-butanediol were enriched in red bean sourdough bread. Sourdough acidification probably promoted interaction of EPS with gluten or red bean proteins through bond interactions to form structures which stabilized gluten in dough and increased water-binding ability in red bean sourdough bread. This study provided a better understanding of the role of EPS in sourdough in improving bread quality and of promising strategies to address consumer demand for nutritious and clean-label products.

Effect of wheat bran dietary fiber on structural properties and hydrolysis behavior of gluten after synergistic fermentation of Lactobacillus plantarum and Saccharomyces cerevisiae

The effect of synergistic fermentation of Lactobacillus plantarum and Saccharomyces cerevisiae on the structural properties and aggregation behavior of gluten containing different wheat bran dietary fiber (WBDF) levels (0, 3, 6, 9, and 12%) was investigated. The results showed that WBDF addition affected the aggregation behavior of gluten at the molecular level, while WBDF significantly induced depolymerization behaviors in large aggregated gluten proteins (Molecular weight > 130 kDa) under reducing conditions (p < 0.05). In terms of secondary structure, WBDF significantly reduced glutamine side chain levels and reduced antiparallel β-sheet structures from 28.57 to 24.53% (p < 0.05). In addition, WBDF thermal properties and its water holding capacity were the main factors causing changes in thermal properties in the overall gluten system. This study provides new data for the improved production of sourdough whole grain and/or high fiber flour products.

Conformational and thermal properties of gluten in wheat dough as affected by bacterial cellulose

Bacterial cellulose (BC), an important category of polysaccharides, was investigated as a texture improver in bakery products. This study focused on the changes in the conformational and thermal properties of gluten in the wheat dough system as affected by BC. Significant reductions in the free-SH content, fluorescence intensity, and surface hydrophobicity index (H₀) were observed as a result of the increased BC addition. The electrophoresis profile (SDS-PAGE) and size exclusion (SE-HPLC) revealed the variation in molecular weight distribution, and the increase in the content of the 40-91 kDa molecular weight was at the expense of a decrease in the amount of the corresponding 10-40 kDa. When 0.1 % BC was added, both the α-helix and β-sheet contents increased as a result of enhanced chemical interactions, thereby contributing to the gluten matrix with higher thermal stability. Further supplementation interfered with the current ordered gluten structure, which could be supported by the lower α-helix/β-sheet content ratio and the decreased degradation temperature (T_d) of gluten with 0.2 % BC. However, the observed decrease in the ratio of β-turns to β-sheets and weight loss at 600 °C indicated that a reconstructed gluten matrix induced by extra BC addition was formed to maintain the structural stability.

Understanding the influence of pullulan on the quality changes, water mobility, structural properties and thermal properties of frozen cooked noodles

Pullulan is widely applied in the food industry due to its unique physicochemical properties, but little information is known about its effects on the quality of frozen cooked noodles (FCNs), nor the underlying mechanism. In this study, the addition of 0.3% and 0.5% pullulan resulted in better texture and cooking properties, and minor chrominance differences, and it significantly (P < 0.05) decreased the freezable water content and retarded the water migration. Pullulan inhibited the depolymerization of the glutenin macropolymer during 0-8 weeks of frozen storage. Meanwhile, pullulan caused slightly decreased α-helixes and increased β-turns, as well as decreased degradation temperature, further suggesting that pullulan influenced the gluten network. A more compact microstructure was shown in the pullulan-fortified FCNs. This study provides a theoretical basis for the positive effects of pullulan on the quality of FCNs from the perspectives of water state and protein structure.

Effect of grape seed power on the structural and physicochemical properties of wheat gluten in noodle preparation system

Noodles were prepared using wheat flour supplemented with 1%, 3%, and 5% grape seed power (GSP). The farinograph properties of wheat flour, the textural properties of the dough, and thermal properties of the gluten were determined. The microstructure was analyzed by scanning electron and atomic force microscopy, and the effects of the addition of GSP on the physicochemical and structural properties (free sulfhydryl content, surface hydrophobic region, and secondary structure) of wheat gluten protein were analyzed. 1% GSP promoted the aggregation of gluten proteins by promoting hydrophobic interactions and hydrogen bonding, thus enhanced the noodle quality. Whereas, 3% and 5% GSP addition disrupted the disulfide bonds between gluten protein molecules and formed macromolecular aggregates linked to gluten proteins through non-covalent bonds and hydrophobic interactions, which prevented the formation of the gluten protein reticulation structure. Our study emphasized the interaction between wheat proteins and GSP in noodle making dough.

Effects of Physical and Chemical Factors on the Structure of Gluten, Gliadins and Glutenins as Studied with Spectroscopic Methods

This review presents applications of spectroscopic methods, infrared and Raman spectroscopies in the studies of the structure of gluten network and gluten proteins (gliadins and glutenins). Both methods provide complimentary information on the secondary and tertiary structure of the proteins including analysis of amide I and III bands, conformation of disulphide bridges, behaviour of tyrosine and tryptophan residues, and water populations. Changes in the gluten structure can be studied as an effect of dough mixing in different conditions (e.g., hydration level, temperature), dough freezing and frozen storage as well as addition of different compounds to the dough (e.g., dough improvers, dietary fibre preparations, polysaccharides and polyphenols). Additionally, effect of above mentioned factors can be determined in a common wheat dough, model dough (prepared from reconstituted flour containing only wheat starch and wheat gluten), gluten dough (lack of starch), and in gliadins and glutenins. The samples were studied in the hydrated state, in the form of powder, film or in solution. Analysis of the studies presented in this review indicates that an adequate amount of water is a critical factor affecting gluten structure.

Wheat Bread Fortification by Grape Pomace Powder: Nutritional, Technological, Antioxidant, and Sensory Properties

Grape pomace powder (GPP), a by-product from the winemaking process, was used to substitute flour for wheat bread fortification within 0, 5, and 10 g/100 g. Rheological properties of control and fortified doughs, along with physicochemical and nutritional characteristics, antioxidant activity, and the sensory analysis of the obtained bread were considered. The GPP addition influenced the doughs' rheological properties by generating more tenacious and less extensible products. Concerning bread, pH values and volume of fortified products decreased as the GPP inclusion level increased in the recipe. Total phenolic compounds and the antioxidant capacity of bread samples, evaluated by FRAP (ferric reducing ability of plasma) and ABTS (2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid)) assays, increased with GPP addition. Moreover, the GPP inclusion level raised the total dietary fiber content of bread. Regarding sensory evaluation, GPP fortification had a major impact on the acidity, the global flavor, the astringency, and the wine smell of bread samples without affecting the overall bread acceptability. The current results suggest that GPP could be an attractive ingredient used to obtain fortified bread, as it is a source of fiber and polyphenols with potentially positive effects on human health.

Physicochemical Effects of Lactobacillus plantarum and Lactobacillus casei Cocultures on Soy-Wheat Flour Dough Fermentation

In contemporary food production, an important role is given to the increase in the nutritional quality of foodstuff. In the bakery industry, one of the main cereals used is wheat flour (WF), which creates bread with proper sensory evaluation but is nutritionally poor. Soy-flour (SF) has increased nutrient content, and its consumption is recommended due to several health benefits. Dough fermentation with lactic acid bacteria (LAB) increases bread shelf life, improves flavor, and its nutritional quality, mostly due to its high organic acid production capability. In the present study, the addition of SF to WF, through fermentation with the cocultures of Lactobacillus plantarum and Lactobacillus casei was analyzed. Three different batches were performed by using WF supplemented with SF, as follows: batch A consisting of 90% WF and 10% SF; batch B-95% WF and 5% SF; batch C-100% WF. The fermentation with these two LABs presented several positive effects, which, together with increased SF content, improved the dough's rheological and physicochemical characteristics. The dynamic rheological analysis exhibited a more stable elastic-like behavior in doughs supplemented with SF (G' 4936.2 ± 12.7, and G″ 2338.4 ± 9.1). Organic acid production changes were the most significant, especially for the lactic, citric, and tartaric content.