Protein polymerization and water mobility in whole-wheat dough influenced by bran particle size distribution

Impact of wheat bran dietary fiber on gluten aggregation behavior in dough during noodle processing

We herein evaluated the impact of adding wheat bran dietary fiber (WBDF) on the aggregation behavior of gluten in dough at various stages of the noodle-making process. Scanning electron microscopy and confocal laser scanning microscopy images confirmed the effective insertion of WBDF particles into the gluten matrix. Importantly, the gap between WBDF and gluten widened during the rolling process. The addition of WBDF led to a reduction in glutenin macropolymer (GMP) content and an elevation in sulfhydryl content, induced the depolymerization behaviors at the molecular level. Additionally, it facilitated the conversion of α-helices and β-turns into β-sheets and random coils within the dough. Moreover, the processing and addition of WBDF contributed to a decrease in weight loss, whereas the degradation temperature remained constant. Resting decreased the sulfhydryl content, whereas sheeting and cutting increased it, further fostering protein depolymerization in the presence of WBDF. These actions significantly increased the β-sheets and random coils content at the expense of β-turns and α-helices content. Significantly, controlled processing emerged as a crucial factor in enhancing gluten depolymerization induced by WBDF in the dough. This comprehensive study provides a nuanced perspective on controlling dough processing to strike a balance between dietary fiber-rich and high-quality foods.

Unraveling the deterioration mechanism of dough during whole wheat flour processing: A case study of gluten protein containing arabinoxylan with different molecular weights

This study aims to the effect of arabinoxylan (AX) on gluten quality. Ultrasonic treatment is utilized to degrade water unextractable arabinoxylans (WUAX) from wheat bran, which obtains three molecular weights of AX. The results indicate that the shear viscosity and particle size of AX were decreased and the ζ-potential was increased after ultrasonic treatment. Analysis of the gluten shows that the free SH of gluten with 6% WUAX, SAX10, and SAX30 (ultrasound duration for 10 min and 30 min) was increased by 51.9%, 48.1%, and 17.0%, respectively, whereas the free SH of 2% SAX30-gluten was increased by 19.8%. Furthermore, WUAX impaired the viscoelasticity properties of gluten, while SAX30 improved the viscoelasticity of gluten. WUAX induced the open, fragile, and discontinuous structure of gluten. On the contrary, SAX30 promoted the formation of the compact and regular gluten structure. Overall, ultrasonic as a non-chemical treatment could be used to improve the quality of whole-wheat foods.

Impact of supplement of Qingke flours on physiochemical properties, sensory and in vitro starch digestibility of wheat bread and its enhancement by bread quality improvers

The aim is to upgrade the formulation to produce wheat bread with lower starch digestibility by supplemented with Qingke flour. Physiochemical properties of multi-scale Qingke flours were examined to select the most satisfied Qingke flour for breadmaking. Data showed multi-scale Qingke samples differed in total starch content, water/oil binding capacity, freeze-thaw stability, but had similar swelling capacity and thermodynamic properties. Addition of Qingke flours significantly reduced the total in vitro starch digestion of bread from 80% to 41% and decreased the rapidly digested starch content from 53% to 27%. However, Qingke flours caused a worse bread quality, texture and sensory e.g. lower bread specific volume (4.26-3.3 mL/g), larger hardness (398-1170 g) and chewiness (296-707 mJ). Meanwhile, hydroxypropyl methylcellulose, sodium stearoyl lactylate and transglutaminase could improve the bread quality and sensory. Lastly, results revealed Qingke-supplemented bread could generate new volatile compounds, hence having a different aroma compared to original wheat bread.

Use of a compound modifier to retard the quality deterioration of frozen dough and its steamed bread

To retard the quality deterioration of the dough during frozen storage, the effects of a compound modifier (CM) comprised of sodium stearoyl lactate, VC, and β-glucanase on the properties of the frozen dough, as well as the quality of the frozen dough steamed bread were investigated. The results revealed that CM restricted the migration of water in the dough and improved its rheological properties. Furthermore, CM minimized the deterioration of specific volume and textural properties, and prevented starch retrogradation in the frozen dough steamed bread. Moreover, the addition of CM strengthened the secondary structure of gluten protein and formed a more resilient gluten network. The microstructure of the frozen dough steamed bread showed that CM reduced the damage caused by ice crystals on the gluten network. Overall, the use of CM strengthened the gluten network and effectively delayed the quality deterioration of the frozen dough, thus is potential as an improver for frozen dough.

Extrusion Modification of Wheat Bran and Its Effects on Structural and Rheological Properties of Wheat Flour Dough

The study investigated the extrusion modification of wheat bran and its effects on structural and rheological properties of wheat flour dough. Extruded bran showed better solubility of dietary fiber and structural porosity, leading to higher hydration and swelling power. Addition of extruded bran to dough caused water redistribution as an intensive aggregation of bound water to gluten matrix with reduced mobility. The bran-gluten interaction influenced by water sequestering caused partial gluten dehydration and conversion of β-turn into β-sheet, which demonstrated the formation of a more polymerized and stable gluten network. Farinographic data confirmed the promotion of dough stability with extruded bran addition at lower gluten content, while viscoelastic data suggested improved dough elasticity at all gluten contents by increasing elastic moduli and decreasing loss tangent. This study would be useful for interpreting the modification effect and mechanism of extrusion on cereal brans and provide valuable guidance for applying it as an effective modification technology on the commercial production of cereal bran and its flour products.

Study of ultrasonic treatment on the structural characteristics of gluten protein and the quality of steamed bread with potato pulp

Physicochemical properties and microstructure of gluten protein, and the structural characteristics of steamed bread with 30 % potato pulp (SBPP) were investigated by ultrasonic treatments. Results showed that 400 W ultrasonic treatment significantly (P < 0.05) increased the combination of water and substrate in the dough with 30 % potato pulp (DPP). The contents of wet gluten, free sulfhydryl (SH), and disulfide bond (SS) were influenced by ultrasonic treatment. Moreover, UV-visible and fluorescence spectroscopy demonstrated that the conformation of gluten protein was changed by ultrasonic treatment (400 W). Fourier transform infrared (FT-IR) illustrated that the β-sheet content was significantly (P < 0.05) increased (42 %) after 400 W ultrasonic treatment, and the surface hydrophobicity of gluten protein in SBPP increased from 1225.37 (0 W ultrasonic treatment) to 4588.74 (400 W ultrasonic treatment). Ultrasonic treatment facilitated the generation of a continuous gluten network and stabilized crumb structure, further increased the specific volume and springiness of SBPP to 18.9 % and 6.9 %, respectively. Those findings suggested that ultrasonic treatment would be an efficient method to modify gluten protein and improve the quality of SBPP.

The use of time domain 1 H NMR to study proton dynamics in starch-rich foods: A review

Starch is a major contributor to the carbohydrate portion of our diet. When it is present with water, it undergoes several transformations during heating and/or cooling making it an essential structure-forming component in starch-rich food systems (e.g., bread and cake). Time domain proton nuclear magnetic resonance (TD ¹ H NMR) is a useful technique to study starch-water interactions by evaluation of molecular mobility and water distribution. The data obtained correspond to changes in starch structure and the state of water during or resulting from processing. When this technique was first applied to starch(-rich) foods, significant challenges were encountered during data interpretation of complex food systems (e.g., cake or biscuit) due to the presence of multiple constituents (proteins, carbohydrates, lipids, etc.). This article discusses the principles of TD ¹ H NMR and the tools applied that improved characterization and interpretation of TD NMR data. More in particular, the major differences in proton distribution of various dough and cooked/baked food systems are examined. The application of variable-temperature TD ¹ H NMR is also discussed as it demonstrates exceptional ability to elucidate the molecular dynamics of starch transitions (e.g., gelatinization, gelation) in dough/batter systems during heating/cooling. In conclusion, TD NMR is considered a valuable tool to understand the behavior of starch and water that relate to the characteristics and/or quality of starchy food products. Such insights are crucial for food product optimization and development in response to the needs of the food industry.

Impact of Native Form Oat β-Glucan on the Physical and Starch Digestive Properties of Whole Oat Bread

To investigate the effect of oat bran on bread quality and the mechanism of reducing the glycemic index (GI) of bread, wheat bran (10%, w/w, flour basis), oat bran (10%), and β-glucan (0.858%) were individually added to determine the expansion of dough, the specific volume, texture, color, GI, starch digestion characteristics, and α-amylase inhibition rate of bread. The results showed that the incorporation of wheat bran and oat bran both reduced the final expanded volume of the dough, decreased the specific volume of the bread, and increased the bread hardness and crumb redness and greenness values as compared to the control wheat group. The above physical properties of bran-containing bread obviously deteriorated while the bread with β-glucan did not change significantly (p < 0.05). The GI in vitro of bread was in the following order: control (94.40) > wheat bran (69.24) > β-glucan (65.76) > oat bran (64.93). Correspondingly, the oat bran group had the highest content of slowly digestible starch (SDS), the β-glucan group had the highest content of resistant starch (RS), and the control group had the highest content of rapidly digestible starch (RDS). For the wheat bran, oat bran, and β-glucan group, their inhibition rates of α-amylase were 9.25%, 28.93%, and 23.7%, respectively. The β-glucan reduced the bread GI and α-amylase activity by intertwining with starch to form a more stable gel network structure, which reduced the contact area between amylase and starch. Therefore, β-glucan in oat bran might be a key component for reducing the GI of whole oat bread.

Recombinant Rice Quiescin Sulfhydryl Oxidase Strengthens the Gluten Structure through Thiol/Disulfide Exchange and Hydrogen Peroxide Oxidation

Recombinant rice quiescin sulfhydryl oxidase (rQSOX) has the potential to improve the flour processing quality, but the mechanisms remain unclear. The effects of rQSOX on bread quality, dough rheology, and gluten structure and composition, with glucose oxidase as a positive control, were investigated. rQSOX addition could improve the dough processing quality, as proved by enhanced viscoelastic properties of dough as well as a softer crumb, higher specific volume, and lower moisture loss of bread. These beneficial effects were attributed to gluten protein polymerization and gluten network strengthening, evidenced by the improved concentration of SDS-insoluble gluten and formation of large gluten aggregates and the increased α-helix and β-turn conformation. Furthermore, decreased free sulfhydryl and increased dityrosine in gluten as well as improved H₂O₂ content in dough suggested that the rQSOX dough strengthening mechanism was mainly based on the formation of disulfide bonds and dityrosine cross-links in gluten by both thiol/disulfide direct exchange and hydrogen peroxide indirect oxidation pathways.

Impact of Fermented Wheat Bran Dietary Fiber Addition on Dough Rheological Properties and Noodle Quality

This study aimed to evaluate the effect of fermented wheat bran dietary fiber (FWBDF) on the rheological properties of the dough and the quality of noodles and to compare it with the effect of the unfermented WBDF (UWBDF). WBDF was fermented with Auricularia polytricha. The results showed that adding UWBDF/FWBDF increased the storage modulus G' and loss modulus G” of the dough, converted α-helices and β-turns into β-sheets and random coils, respectively, inhibited water flow, increased cooking loss, and decreased the maximum resistance in the noodles. The formed gluten network had a more random and rigid structure, resulting in the deterioration of the quality of noodles. Furthermore, the number of α-helices and the peak proportions of weakly bound water A₂₂ increased but the number of β-sheets and cooking loss decreased in the FWBDF group compared with the UWBDF group. FWBDF (≤4%) improved the hardness of noodles, while UWBDF decreased it. These changes indicated that fermentation could reduce the destructive effects of WBDF on the quality of noodles, providing a new perspective on balancing dietary fiber-rich and high-quality foods.

Effects of Wheat Bran Micronization on the Quality of Reconstituted Whole-Wheat Flour and Its Cooked Noodles

The particle size of wheat bran plays an important role in the quality of reconstituted whole-wheat flour and its products. The effects of wheat bran particle size on the quality of reconstituted whole-wheat flour and its cooked noodles were analyzed; the mean particle size (D50) of wheat bran ranged from 26.05 to 46.08 μm. Results show that the decreases in D50 of wheat bran induced the changes in the quality of whole-wheat flour and its noodles. Specifically, the damaged starch content, water absorption, and the solvent retention capacity of sodium carbonate and sucrose of whole-wheat flour increased at various degrees, while pasting viscosity decreased, and the gluten index and SDS-sedimentation volume increased first and then decreased. The cooking yield, cooking loss, and break rate of fresh noodles decreased first and reached a trough at D50 of 26.05 μm, and then increased. The adhesiveness of cooked noodles increased, the score of smoothness, taste, appearance, and color increased to a stable value, but the hardness, springiness, cohesiveness, resilience, firmness score, and elasticity score increased first and then decreased. These turning points of changing trends of indexes mostly occurred when the D50 of wheat bran was 26.51 μm. In conclusion, whole-wheat noodles with wheat bran of D50 of 26.51 μm addition exhibit better cooking, textural, and sensory properties than those with smaller or larger wheat bran. Excessive crushing of wheat bran not only costs highly in terms of energy, but also has a negative impact on the quality of the noodles.

Quality Characteristics and Antioxidant Activity of Fresh Noodles Formulated with Flour-Bran Blends Varied by Particle Size and Blend Ratio of Purple-Colored Wheat Bran

This study explored the noodle-making performance of flour blends with different particle sizes and blending ratios of purple-colored wheat bran and their antioxidant properties. The bran particle size was reduced using an ultra-centrifugal mill equipped with 1, 0.5, and 0.2 mm sieves. The damaged starch and swelling capacity of the bran were analyzed. Quality of the flour-bran blends at different blending ratios was analyzed by solvent retention capacity (SRC). Noodles made from the blends and their corresponding antioxidant activities were examined. The damaged starch and swelling capacity of bran were higher for smaller particles than for larger particles. Water and sodium carbonate SRC values of blends increased as the bran particle size decreased. The smaller the bran particles incorporated in the cooked noodles, the greater firmness and springiness measured. The antioxidant activity of noodles made with blends reflected better embedding of the small particles of bran than the large particles into noodle sheets. Small bran particles significantly enhanced noodles’ quality and antioxidant activity at higher blending ratios than large bran particles. Particle size reduction of bran enhanced the noodle-making performance of flour blended with purple-colored wheat bran; this could increase the utilization of bran to produce noodles with health benefits.

Whole-flours from hard and soft wheat genotypes: study of the ability of prediction test to estimate whole flour end-use

The aims of this work were to assess the influence of the physicochemical composition of whole flour from soft and hard wheat genotypes on cookie and bread properties, as well as the ability of the prediction tests to estimate the whole meal flour end-use. Flours from hard and soft wheat genotypes proved to have different chemical composition and particle size distribution. Flours from hard wheat had lower particle average size and dietary fiber content, and higher lipid and wet gluten contents than flours from soft wheat. Particle size distribution, water absorption capacity and chemical composition of whole flours strongly influenced bread and cookie making performance. Considering prediction tests, flours from different wheat types were successfully discriminated using SDS-SI, SRC lac, and GI. However, rather weak correlations were found between the prediction test and the cookie and bread quality parameters. The prediction test, standardized for refined flours, showed a poor performance when whole flours were used. Nevertheless, grain texture and whole flour physicochemical properties did affect bread and cookie quality parameters, thus classical prediction tests should be modified in order to estimate the end-use performance of whole flours. Moreover, a standardization of the milling process should be considered.

Insight into molecular and rheological properties of sprouted sorghum flour

This work investigated the effect of sprouting and drying post-sprouting on technological functionalities of sorghum flour as probed by Low-resolution Proton Nuclear Magnetic Resonance (¹H NMR) and Dynamic Mechanical Analysis (DMA). Multivariate statistics were used to assess the effect of flour (from sprouted and unsprouted sorghum, and wholewheat) and hydration level on flour-water systems molecular and viscoelastic properties. Overall, sorghum-based systems showed greater molecular mobility explaining poorer viscoelastic properties than those obtained from wheat. Sprouting affected the molecular properties of sorghum flour-water systems, while no differences were observed in the two sprouted samples dried in different conditions. However, sprouting did not affect the viscoelastic properties of sorghum-water systems. These results bolster the use of sprouted sorghum in composite flours for the development of sustainable finished products with high nutritional value and satisfactory technological and organoleptic properties.

Effects of the size distribution of wheat starch on noodles with and without gluten

To understand the effects of A- and B-type wheat starch on noodle quality, two noodle models with (Model 1) and without (Model 2) gluten were constructed with five different ratios of A- to B-granules (100A-0B, 75A-25B, 50A-50B, 25A-75B, and 0A-100B). With increasing proportions of B-granules, the noodle structures of Models 1 and 2 became increasingly dense. The cooking loss, water absorption, proportion of free water, chewiness, cohesiveness and resilience decreased from 35.64 to 15.49%, 240.92 to 228.58%, 88.89 to 85.98%, 21.93 to 13.24 N, 0.77 to 0.56, and 0.61 to 0.36, respectively, with the increased proportion of B-granules in Model 2, while those parameters normally presented "V" or inverted "V" trends in Model 1. Compared to their counterparts in Model 2, gluten networks with 25-50% B-granules had an outstanding ability to increase the percentage of tightly bound water, hardness, chewiness and springiness by 4.50%, 24.07 N, 25.05 N, and 0.17 at most and reduce the proportion of free water and water absorption by 5.56 and 73.70% at most, respectively. The results indicated that the effect of the gluten network on noodle qualities may partially depend on its structure, which is shaped by the granule size distribution. Compared to the other characteristics of noodles, the springiness was influenced by a more complicated mechanism involving A- and B-granules in Model 2, while it was strongly affected by the gluten network under the given experimental conditions in Model 1.

Use of the 1H NMR technique to describe the kneading step of wholewheat dough: The effect of kneading time and total water content

The kneading step of wholewheat flour (WWF) dough was monitored using low-resolution ¹H nuclear magnetic resonance (NMR). The tested variables were kneading time and total water content. Two ¹H Free induction decay (FID) (A and B) and four ¹H T₂ Car-Purcell-Meiboom-Gill (CPMG) (C, D, E and F) proton populations were observed and the attribution to the different proton domains was made based on the literature and data acquisition. Kneading time significantly increased the mobility and the relative abundance of popA, the relative abundance and strength of protons of popC, D and E, while significantly reducing the relative amount of popF and increasing its mobility. This evolution of the proton populations during kneading was interpreted as chemical/physical transformations of the flour constituents. The use of WWF may reveal the changes in molecular dynamics underlying the higher water requirements of unrefined doughs, often associated with improved bread quality.

Protein polymerization in dumpling wrappers influenced by folding patterns

The influences of folding patterns on the protein polymerization in dumpling wrappers were investigated. The dumpling dough sheet after the compounding rollers was folded with various patterns (control with no angle, 15°, 25°, 35° and 45° folding), before going through the sheeting and reduction rolls. Protein secondary structure, free sulfhydryl content, protein electrophoretic profiles, and texture of dumpling wrappers were determined. Results showed that folding could increase the proportion of α-helix conformation, and produce dumpling wrappers with enhanced toughness but reduce wrapper extensibility. The wrapper with 45° folding showed lower -SH content than the control and other folding angles. However, only a few variations in SDS band pattern and intensities were observed at the molecular weight position of around 35 kDa. Briefly, folding process could influence the gluten formation during the preparation of dumpling wrappers; the folding angle at 45° produced stronger gluten network and tougher wrappers.

The thermal stability, structural changeability, and aggregability of glutenin and gliadin proteins induced by wheat bran dietary fiber

Wheat bran dietary fiber (WBDF) has been reported to be responsible for the low quality of whole wheat flour products due to its destructive effect on the gluten matrix. Glutenin and gliadin are the major components of gluten protein and contribute to a proper gluten structure. In this study, the thermostability, surface hydrophobicity, fluorescence characteristics, free sulfhydryl contents, and molecular weight distributions of glutenin- and gliadin-rich fractions were determined after the addition of WBDF. The addition of WBDF to glutenin resulted in an increased surface hydrophobicity and free sulfhydryl content, as well as a red-shift of the fluorescence spectrum. However, the WBDF-modified gliadin fraction changed slightly mainly due to its spherical conformation. Size exclusion chromatography profiles revealed increasing soluble gliadin aggregates and decreasing high molecular weight glutenin fractions as a result of WBDF incorporation. The results from the thermostability analyses exhibited decreased weight loss and decomposition temperatures for both glutenin and gliadin proteins at high WBDF concentration. Our results suggest that changes in the gluten matrix caused by WBDF may largely rely on glutenin structure variation.

Effects of Milling Methods and Cultivars on Physicochemical Properties of Whole-Wheat Flour

The aim of the present study was to investigate the influence of milling methods (jet mill (JM) and hammer mill (HM)) and wheat cultivars (Keumkang (K), Jokyung (J), and Anzunbaengi (A)) on physicochemical and dough properties of whole-wheat flour (WWF). The color, particle size, starch damage (SD), falling number (FN), water absorption index (WAI), water solubility index (WSI), pasting and Mixolab® properties, and dough extensibility of WWF were measured. Significant differences were observed in proximate compositions as well as in color, particle size, FN, and WAI between the distinct milling methods and cultivars (p<0.001). The particle sizes of each cultivar milled with a HM (K: 188.5 µm; J: 115.7 µm; A: 40.34 µm) were larger than those milled with a JM (K: 41.8 µm; J: 50.7 µm; A: 20.8 µm). The final viscosity of WWF milled with a HM (K: 1304 cP; J: 1249 cP; A: 1548 cP) was higher than that of cultivars milled with a JM (K: 1092 cP; J: 1062 cP; A: 994 cP). Dough extensibility and resistance to extension also differed among the cultivars, and the C2 Mixolab® parameter (an indicator of protein weakening) was influenced by the milling method. Overall, results from principal component analysis showed that, among the three cultivars, Keumkang WWF was the most affected by the milling method.

Thermo-mechanical properties of dough enriched with wheat bran from different wheat variety

Wheat bran is the by-product derived from the wheat milling and represents a good source of dietary fiber. Consumption of wheat bran is associated with many health benefits. The hydration properties (water holding, water retention and swelling capacity) and oil binding capacity of bran from various wheat variety were investigated. It was showed that the water holding capacity of bran ranged from 2.27 to 2.98 g.g-1, which were approximately four times higher compared to wheat flour. Also, it was observed that commercial wheat bran was characterised with the highest swelling capacity (5.21 mL.g-1) and the lowest water retention and oil binding capacities (1.38 and 1.35 g.g-1, respectively). Mixing and pasting properties of wheat dough with addition of bran at different level (5, 10 and 15%) were studied using Mixolab. From the results it was concluded that water absorption and dough development time increased with addition of different bran, while dough stability decreased. Moreover, with increasing addition level of different bran significantly affected the thermo-mechanical properties of wheat dough. The lowest effect on protein weakening was found after addition of spelt bran. The higher starch pasting ability of enriched dough was recorded after incorporation of bran from crossbreed Lubica. Furthermore, it was found that dough enriched with the commercial wheat bran was characterized by the lowest values of C3 (lower starch pasting ability), C4 (lower stability of hot formed gel) and C5 (lower starch retrogradation) parameters.