Konjac glucomannan-induced changes in thiol/disulphide exchange and gluten conformation upon dough mixing

Aqueous ozone effects on wheat gluten: Yield, structure, and rheology

This study investigates the impact of aqueous ozone (AO) on the yield, molecular structure, and rheological properties of wheat gluten separated using the batter procedure. Employing strong gluten flour (SGF) and weak gluten flour (WGF), we demonstrate that AO pretreatment significantly enhances the yield and purity of separated starch and gluten. Surface hydrophobicity, free sulfhydryl groups, Fourier transform infrared spectroscopy (FTIR), Raman, and size exclusion-high-performance liquid chromatography (SE-HPLC) analyses were used to evaluate the effects of AO on the molecular structure of gluten. Our analysis reveals that low concentrations of AO induce specific modifications in gluten proteins. AO treatment increases cross-linking in glutenin macropolymer (GMP), reduces surface hydrophobicity, and stabilizes secondary and tertiary structures. These changes include an increase in β-sheet content by approximately 9% and a corresponding decrease in β-turn structures, leading to enhanced viscoelastic properties of the gluten. The research highlights AO's potential as a sustainable and efficient agent in wheat flour processing, offering advancements in both product quality and eco-friendly processing techniques. Future research should optimize AO treatment parameters and explore its effects on different cereal types further to enhance its applicability and benefits in food processing. PRACTICAL APPLICATION: Our work substantially advances the existing knowledge on wheat flour processing by demonstrating the multifaceted benefits of AO pretreatment. We unveil significant improvements in the yield and purity of starch and gluten when compared to conventional separation methods. Moreover, our in-depth analysis of molecular changes induced by AO, including increased cross-linking, alterations in surface hydrophobicity, and modifications in glutenin macropolymer content, provides new insights into how AO affects the viscoelastic properties of gluten. This contribution is pivotal for the development of more efficient, sustainable, and eco-friendly wheat flour processing technologies.

Stereo-hindrance effect and oxidation cross-linking induced by ultrasound-assisted sodium alginate-glycation inhibit lysinoalanine formation in silkworm pupa protein

Silkworm pupa protein isolate (SPPI) is rich in amino acids, making it chemically reactive, degradable, and easy to form lysinoalanine (LAL). We investigated how conformational cross-linking, induced by ultrasound-assisted sodium alginate, could inhibit the formation of LAL during the preparation of SPPI. Glycoconjugated SPPI (using 1 % sodium alginate under ultrasonication) showed the lowest LAL content i.e., 7.403 μg·mg-1, representing a 49.58 % decrease, with reference to the control. The ionic, hydrogen, and covalent bonds in the glycoconjugate increased by 171.79 %, 8.48 %, and 35.56 %, respectively. Glycation decreased arginine by 28.92 % and caused the oxidation of tyrosine, methionine and proline to form carbonyl groups. Some precursor amino acids, including lysine, serine, cysteine and threonine were not degraded during the combined treatment. The macromolecular aggregation caused by structural modifications strengthened the steric resistance of LAL cross-linking. The study outcomes provide a novel approach and theoretical basis for inhibition of LAL formation in SPPI.

Adenosine monophosphate boosts the cryoprotection of ultrasound-assisted freezing to frozen surimi: Insights into protein structures and gelling behaviors

Ultrasound-assisted freezing (UAF) is a clean technique for meat cryoprotections; however, its effectiveness is still limited compared to conventional cryoprotectants, e.g., sugars, polyols, especially at high dosages. To resolve this problem, a synergistic cryoprotection strategy was developed in this study. Adenosine monophosphate (AMP), an adenosine-type food additive, was introduced into frozen surimi at a considerably reduced content (0.08%), yet substantially enhanced the efficiency of UAF to comparable levels of commercial cryoprotectant (4% sucrose with 4% sorbitol). Specifically, UAF/AMP treatment retarded denaturation of surimi myofibrillar protein (MP) during 60-day frozen storage, as evidenced by its increased solubility, Ca2+-ATPase activity, sulfhydryl content, declined surface hydrophobicity, particle size, and stabilized protein conformation. Gels of UAF/AMP-treated surimi also demonstrated more stabilized microstructures, uniform water distributions, enhanced mechanical properties and water-holding capacities. This study provided a feasible approach to boost the cryoprotective performance of UAF, thus expanding its potential applications in frozen food industry.

Effect of highland barley treated with heat-moisture on interactions between gluten and starch granules in dough

This study aimed to investigate the effect of heat-moisture treatment (HMT)-modified highland barley (HB) on interactions between gluten and starch granules in dough. The results demonstrated that HB addition increased the water absorption, weakened the extensibility, increased the storage modulus (G') and loss modulus (G″), decreased tan δ (G"/G') of dough. The textural and stress relaxation results showed that HB increased the hardness and elastic modulus (E2) of the dough, requiring more stress to compress the dough. Also, the increase in sulfhydryl and surface hydrophobicity all confirmed the addition of HB induced the deterioration of gluten network structure. Furthermore, HMT-HB improved farinograph quality number of flour, decreased tan δ of dough compared with HB. The E2, coefficient of viscosity (η) and hardness increased, while the relaxation time (τ) decreased with increasing HMT strength of HB, suggesting the formation of a tighter dough structure. The secondary structure and microstructure analyses revealed that the HMT could reduce the damage of HB to dough quality. These results indicated that HMT had the potential to enhance the interaction between starch and protein, leading to a denser dough matrix. This study facilitates the basic theory for the comprehensive utilization of HB in the food industry.

Rheological, thermal, and structural properties of heat-induced gluten gel: Effects of starch with varying degrees of debranching

This study evaluated the effects of starch with varying degree of debranching on the rheological, thermal, and structural properties of heat-induced gluten gel. As the duration of starch debranching treatment increased from 0 to 8 h, the viscoelasticity of the gel containing debranched starch (DBS) improved. Compared with the gluten gel (G), the gel strength of the G + DBS (8 h) sample increased by 65.2 %. The degradation temperature of gluten was minimally affected by DBS, while the weight loss rate increased by 4.4 %. Furthermore, the α-helical structure of gluten decreased, concomitant with an increase in β-sheet content. Notably, DBS treated for 8 h exhibited more hydrogen bonds with the tyrosine of gluten and triggered disulfide bridge conformation to transition from g-g-g to t-g-g, thereby reducing the stability of the molecular conformation of gluten proteins, as evidenced by the decreased height and width of the molecular chains observed in atomic force microscopy images. Overall, the composite gel structure induced by DBS exhibited a more continuous and homogeneous owing to the improved compatibility between DBS and gluten proteins, favoring the formation of a robust gel. These findings provide valuable insights for utilizing DBS to enhance gluten gel properties.

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.

Interaction of wheat bran dietary fiber-gluten protein affects dough product: A critical review

Wheat bran dietary fiber (WBDF) is an emerging food additive used for improving the nutritional value of dough products, albeit its adverse effects cannot be ignored. The dilution effect, mechanical shear effect, competitive water absorption, and steric hindrance of WBDF, as well as the non-covalent binding between WBDF and gluten protein, are considered the key mechanisms underlying the WBDF-gluten protein interaction. However, current studies on the interaction are mostly limited to the impact of the interaction on gluten protein and are rarely focused on the quality of products. Therefore, the effects of the interaction on the structural characteristics and aggregation behavior of gluten protein and multiple involved mechanisms are discussed in this review. On this basis, these changes are systematically related to the gluten network structure, dough properties, and product quality. Mitigation measures corresponding to negative impacts also need to be elaborated to guide and standardize the production and development of dough products containing WBDF.

Effect of heat treatment on conformation and aggregation properties of wheat bran dietary fiber-gluten protein

To understand the heat mediated cross-linking mechanism of gluten in the presence of wheat bran dietary fiber (WBDF), the effect of heat treatment on conformation and aggregation properties of wheat bran dietary fiber-gluten protein was comparatively investigated in this study. The results showed G' and G" increased after adding WBDF, then decreased after heating. The SE-HPLC, chemical interaction and surface hydrophobicity analysis revealed the WBDF participated in the rearrangement of intermolecular interactions and induced depolymerization behavior behavior of gluten via disulfide and non-covalent bonds at low temperatures (25 °C and 60 °C), but heating (at 95 °C) promoted these interactions via disulfide bonds. Besides, changes in the secondary structure of gluten protein induced by WBDF during heating were correlated with the steric hindrance and hydroxyl groups on WBDF. These results suggested that WBDF impeded the cross-linking and aggregation of gluten through the rearrangement of chemical bonds and physical entanglements, then this effect was weakened at high temperatures, most likely by improving the disulfide bonds among gluten proteins. This study consummates the understanding of the cross-linking mechanisms of gluten with WBDF during heating, and provides the theoretical basis for improving the quality and acceptability of whole wheat-based products.

Interaction with wheat starch affect the aggregation behavior and digestibility of gluten proteins

Understanding the interplay between gluten and wheat starch is crucial for elucidating the digestibility mechanism of gluten in wheat-based products. However, this mechanism remains under-investigated. This study sought to elucidate the influence of starch-induced protein structural modifications on gluten digestion. Our findings revealed that starch considerably enhanced gluten digestion. In the presence of starch, gluten protein digestibility increased from 10.91 % (in the control group with a gluten-to-starch ratio of 1:0) to 14.40 % (in the complex with a gluten-to-corn starch ratio of 1:1). The diminished gluten protein digestibility due to starch may be ascribed to modifications in protein configuration and aggregation behavior. Morphological studies suggested that starch not only functioned as filler particles but also diluted the gluten matrix. A protein network assessment further affirmed that both the junction density and branching rate of gluten proteins decreased notably by 29.9 % and 25.1 %, respectively. Conversely, lacunarity increased by 1.92-fold, compromising the cohesiveness and connectivity of the gluten matrix. Elevated starch concentrations suppressed the formation of disulfide bonds, impeding gluten protein aggregation. Concurrently, gluten-starch interactions were governed by hydrogen bonds and hydrophobic associations. In summary, starch augmented gluten protein digestibility by curtailing their polymerization. This revelation might offer novel perspectives on optimizing gluten protein digestion and utilization.

Structure-activity relationship between gluten and dough quality of sprouted wheat flour based on air classification-induced component recombination

BACKGROUND

Air classification can separate sprouted wheat flour (SWF) into three types: coarse wheat flour (F1), medium wheat flour (F2) and fine wheat flour (F3). The gluten quality of SWF can be indirectly improved by removing inferior parts (F3). In order to reveal the underlying mechanism of this phenomenon, the composition and structural changes of gluten, as well as the rheological properties and fermentation characteristics of gluten in recombinant dough in the process of air classification of all three SWF types, were analyzed in this study.

RESULTS

Overall, sprouting significantly reduced the content of high-molecular-weight subunits, such as glutenin subunit and ω-gliadin. It also destroyed the structural content, such as disulfide bonds, α-helix and β-turn contents, which maintained the stability of gluten gel. Air classification made the above changes in F3 more severe but reversed them in F1. Moreover, rheological properties were more affected by gluten composition, whereas fermentation characteristics were more affected by gluten structure.

CONCLUSION

After air classification, particles rich in high molecular weight subunits from SWF are enriched in F1, and the gluten of F1 has more secondary structure that maintain gel stability, which ultimately lead to improved rheology properties and fermentation characteristics. F3 relatively exhibits the opppsite phenomenon. These results further reveal the potential mechanism of improvement of SWF gluten by air classification. Moreover, Thus, this study provides new perspectives for the utilization of SWF. © 2023 Society of Chemical Industry.

Synergistic effects of oxidized konjac glucomannan on rheological, thermal and structural properties of gluten protein

Oxidation is an effective way to prepare depolymerized konjac glucomannan (KGM). The oxidized KGM (OKGM) differed from native KGM in physicochemical properties due to different molecular structure. In this study, the effects of OKGM on the properties of gluten protein were investigated and compared with native KGM (NKGM) and enzymatic hydrolysis KGM (EKGM). Results showed that the OKGM with a low molecular weight and viscosity could improve rheological properties and enhance thermal stability. Compared to native gluten protein (NGP), OKGM stabilized the protein secondary structure by increasing the contents of β-sheet and α-helix, and improved the tertiary structure through increasing the disulfide bonds. The compact holes with shrunk pore size confirmed a stronger interaction between OKGM and gluten protein through scanning electron microscopy, forming a highly networked gluten structure. Furthermore, OKGM depolymerized by the moderate ozone-microwave treatment of 40 min had a higher effect on gluten proteins than that by the 100 min treatment, demonstrating that the excessive degradation of KGM weakened the interaction between the gluten protein and OKGM. These findings demonstrated that incorporating moderately oxidized KGM into gluten protein was an effective strategy to improve the properties of gluten protein.

Classification, gelation mechanism and applications of polysaccharide-based hydrocolloids in pasta products: A review

Polysaccharide-based hydrocolloids (PBHs) are a group of water-soluble polysaccharides with high molecular weight hydrophilic long-chain molecules, which are widely employed in food industry as thickeners, emulsifiers, gelling agents, and stabilizers. Pasta products are considered to be an important source of nutrition for humans, and PBHs show great potential in improving their quality and nutritional value. The hydration of PBHs to form viscous solutions or sols under specific processing conditions is a prerequisite for improving the stability of food systems. In this review, PBHs are classified in a novel way according to food processing conditions, and their gelation mechanisms are summarized. The application of PBHs in pasta products prepared under different processing methods (baking, steaming/cooking, frying, freezing) are reviewed, and the potential mechanism of PBHs in regulating pasta products quality is revealed from the interaction between PBHs and the main components of pasta products (protein, starch, and water). Finally, the safety of PBHs is critically explored, along with future perspectives. This review provides a scientific foundation for the development and specific application of PBHs in pasta products, and provides theoretical support for improving pasta product quality.

Combined effect of konjac glucomannan addition and ultrasound treatment on the physical and physicochemical properties of frozen dough

The effects of dual sequential modification using konjac glucomannan and ultrasound treatments at power densities of 15-37.5 W/L on the hydration, rheology and structural characteristics of frozen dough were investigated in this study. The results revealed that the konjac glucomannan and ultrasound treatments improved the textural properties of frozen dough, but had a negative impact on its viscoelasticity. Furthermore, konjac glucomannan and ultrasound treatments increased the content of free sulfhydryl group and disulfide bond, as well as improved the freeze tolerance of dough. The results exhibited that the enthalpy of frozen dough decreased by 20.42 % compared with the frozen blank control dough under ultrasonic power density of 22.5 W/L. The network structure of frozen dough treated by konjac glucomannan and ultrasound was more ordered and integral than that of frozen blank control dough. These results provide valuable knowledge on the application of konjac glucomannan and ultrasound to frozen wheat-based foods.

Effect of konjac glucomannan on aggregation patterns and structure of wheat gluten with different strengths

Konjac glucomannan (KGM) can act as a food additive to improve the quality of dough. The effects of KGM on the aggregation patterns and structural properties of weak, middle, and strong gluten were studied. We found that with a higher proportion of KGM substitution (10%), the aggregation energy of middle and strong gluten became lower than the control samples, while exceeding the control for weak gluten. With 10% KGM, aggregation of glutenin macropolymer (GMP) was enhanced for weak gluten, but suppressed for middle and strong gluten. The α-helix transferred to β-sheet in weak, but caused more random-coil structures for middle and strong gluten induced by 10% KGM. With 10% KGM, the network for weak gluten became more continuous, but severely disrupted for middle and strong gluten. Thus, KGM has distinct effects on weak, middle, and strong gluten, which related to the alteration of gluten secondary structures and GMP aggregation pattern.

Effect of hydrocolloids on gluten proteins, dough, and flour products: A review

Hydrocolloids are among the most common components in the food industry, which are used for thickening, gel formation, emulsification, and stabilization. Previous studies have also found that hydrocolloids can affect the structures and properties of gluten proteins, dough, and flour products. In this review, hydrocolloids were separated into three categories: anionic, nonionic, and other hydrocolloids, and reviewed the effects of common hydrocolloids on gluten proteins, dough, and flour products. Hydrocolloids can affect the structures and properties of gluten proteins through gluten-hydrocolloids interaction, secondary structures, disulfide bonds, environment of aromatic amino acids, and chemical bonds. The properties of dough are affected by rheological, fermentation, and thermomechanical properties. Hydrocolloids are widely used in bread, Chinese steamed bread, noodles, yellow layer cake, and so on, which mainly affect their appearance, texture, and aging speed. This comprehensive review provides a scientific guide for the development and utilization of hydrocolloids and their applications in flour products, and provides a theoretical basis for improving the processing characteristics of products.

Characterization of sonicated gluten protein and subsequent rheological properties of model dough and noodles

BACKGROUND

The present study aimed to investigate the effects of the thermo-mechanical and rheological properties of a wheat gluten-sonicated model dough and noodles, as well as the effects of ultrasonic frequency (20, 28, 40, 68 and 80 kHz) on the functional properties and structural features of gluten.

RESULTS

Water absorption, stability and developmental time, and viscoelastic behavior of gluten-sonicated model dough were all found to be improved. Water absorption, tensile resistance and stretching distance of noodles increased markedly, whereas cooking loss decreased. Ultrasonication at different frequencies also significantly affected gluten structure, including its surface hydrophobicity, micro-network structure, and secondary and tertiary structures. These alterations then caused changes in its functional characteristics. Compared to untreated gluten, sonicated gluten exhibited significantly increased oil and water capacities (8.75-15.26% and 100.65-127.71% higher than the untreated gluten, respectively), foaming and emulsifying properties, and increased solubility (63.46-98.83% higher than control). In addition, these findings indicated that 40 kHz was the likely resonance frequency of the cavitation bubble in the gluten solution. However, sodium dodecyl sulfate-polyacrylamide gel electrophoresis electropherograms revealed that such treatments did not affect the molecular weight of gluten, which was also consistent with its unchanged disulfide bond content.

CONCLUSION

The present study clarified the impact of frequency on the properties of gluten and model dough. The best frequency for modification of gluten was 40 kHz. Collectively, these findings suggest that ultrasonic technology has the potential for use in modifying wheat gluten and commercial noodle processing. © 2022 Society of Chemical Industry.

Effects of Amylopectins from Five Different Sources on Disulfide Bond Formation in Alkali-Soluble Glutenin

Wheat, maize, cassava, mung bean and sweet potato starches have often been added to dough systems to improve their hardness. However, inconsistent effects of these starches on the dough quality have been reported, especially in refrigerated dough. The disulfide bond contents of alkali-soluble glutenin (ASG) have direct effects on the hardness of dough. In this paper, the disulfide bond contents of ASG were determined. ASG was mixed and retrograded with five kinds of amylopectins from the above-mentioned botanical sources, and a possible pathway of disulfide bond formation in ASGs by amylopectin addition was proposed through molecular weight, chain length distribution, FT-IR, ¹³C solid-state NMR and XRD analyses. The results showed that when wheat, maize, cassava, mung bean and sweet potato amylopectins were mixed with ASG, the disulfide bond contents of alkali-soluble glutenin increased from 0.04 to 0.31, 0.24, 0.08, 0.18 and 0.29 μmol/g, respectively. However, after cold storage, they changed to 0.55, 0.16, 0.26, 0.07 and 0.19 μmol/g, respectively. The addition of wheat amylopectin promoted the most significant disulfide bond formation of ASG. Hydroxyproline only existed in the wheat amylopectin, indicating that it had an important effect on the disulfide bond formation of ASG. Glutathione disulfides were present, as mung bean and sweet potato amylopectin were mixed with ASG, and they were reduced during cold storage. Positive/negative correlations between the peak intensity of the angles at 2θ = 20°/23° and the disulfide bond contents of ASG existed. The high content of hydroxyproline could be used as a marker for breeding high-quality wheat.

Study on the quality characteristics of hot-dry noodles by microbial polysaccharides

The effect of curdlan gum (CG), gellan gum (GG), and xanthan gum (XG) on the quality characteristics of hot-dry noodles (HDN) was investigated. The rheology properties were used to evaluate the quality of the dough, the textural, viscosity, cooking characteristics and water states were investigated to study the quality changes of HDN. Three microbial polysaccharides were found that it could improve the quality of wheat flour and significantly increase the starch viscosity of HDN and delay the water migration rate of HDN. When 0.2% CG, 0.5% GG, and 0.5% XG were added, the HDN showed the best flour swelling power, texture, and tensile properties, and the structure of gluten network was significantly improved. The flourier transform infrared spectroscopy results showed that microbial polysaccharides with appropriate concentrations changed the formation of hydrogen bond in HDN, decreased α-helix and increased β-turn content. Meanwhile, the relative continuous and complete gluten network was formed, which could be proven by microstructure observation. This study provides a reference for functionality applications of HDN with microbial polysaccharides.

Effect of konjac glucomannan with different viscosities on the quality of surimi-wheat dough and noodles

It was investigated that the rheology, starch-gluten-surimi network, thermal properties, and water distribution of surimi-wheat dough, and texture characteristics, cooking properties, and microscopic characteristics of the surimi-wheat noodles with konjac glucomannan (KGM) of different viscosities in different concentrations. The results showed that the storage (G'), loss (G″), and complex (G⁎) moduli of dough increased with adding KGM. With the increase of KGM viscosity, the reduction in the free sulfhydryl (SH) content to 0.84 μmol/g and the increase in the free water content to 8.25 % led to significantly improved enthalpy and the microstructure density. The hardness and tensile length of noodles were substantially increased by adding 3 % KGM. In addition, the KGM enhanced the starch-gluten-surimi network and improved the cooking qualities and textural properties of noodles. More importantly, the application of KGM in the wheat flour composite system also showed better performance. Thus, the introduction of KGM into the surimi-wheat dough had a significant effect on the optimization of the macro- and micro-characteristics of dough and noodles.

Impact of Wheat Arabinoxylan with Defined Substitution Patterns on the Heat-Induced Polymerization Behavior of Gluten

To further depict the interaction mechanism of wheat arabinoxylan (AX) and gluten proteins upon thermal processing, AX was enzymatically tailored with defined substitution patterns and the impact on the heat-induced polymerization behavior of gluten was comparatively studied. The results showed that tailormade AX promoted the formation of glutenin-glutenin and glutenin-gliadin macrocrosslinks upon heating, with the optimal effect detected for AX depleted of Araf of disubstituted Xylp. The tailormade AX, especially AX depleted of monosubstituted Xylp, facilitated the polymerization ability of α-gliadin into glutenin compared with untailored AX. The unfolding process of gluten was partially impeded by AX upon heating, while the tailormade AX promoted the unfolding process. AX could bury Trp and Tyr upon polymerization of glutenin and gliadin and induced the change of the disulfide bridge conformation to a less-stable state, while the effect was alleviated with tailormade AX. The enhanced polymerization with tailormade AX strengthened the gluten network and induced more heterogeneously distributed large protein aggregates.

Investigation of the Effect of Rice Bran Content on the Antioxidant Capacity and Related Molecular Conformations of Plant-Based Simulated Meat Based on Raman Spectroscopy

At present, plant-based simulated meat is attracting more and more attention as a meat substitute. This study discusses the possibility of partial substitution of rice bran (RB) for soybean protein isolate (SPI) in preparing plant-based simulated meat. RB was added to SPI at 0%, 5%, 10%, 15%, and 20% to prepare RB-SPI plant-based simulated meat by the high moisture extrusion technique. RB-SPI plant-based simulated meat revealed greater polyphenol content and preferable antioxidant capacity (DPPH radical scavenging capacity, ABTS scavenging ability, and FRAP antioxidant capacity) compared to SPI plant-based simulated meat. The aromatic amino acids (tryptophan and tyrosine) of RB-SPI plant-based simulated meats tend to be masked first, and then the hydrophobic groups are exposed as RB content increases and the polarity of the surrounding environment increases due to the change in the disulfide conformation of RB-SPI plant-based simulated meats from a stable gauche-gauche-gauche conformation to a trans-gauche-trans conformation.

Effect of chemical structure of selected phenolic acids on the structure of gluten proteins

Effect of overmixing process and structure of selected phenolic acids belonging to hydroxycinnamic and hydroxybenzoic group on the structure of gluten network were analysed with application of FT-Raman Spectroscopy. Modification of gluten by acids resulted in formation of aggregates and unordered structures at the expense of protein stabilizing structures (e.g. β-sheets or β-turns). Supplementation with most of the acids caused reduction in the amount of disulphide bonds in the most stable conformation (g-g-g). Changes in the molecular organization of gluten proteins depended on the chemical structure of particular acids. The presence of bands assigned to aggregates was connected with the number of OH groups present at the aromatic ring of the acids. Acids belonging to hydroxycinnamic group did not incorporate or incorporate only partially into gluten network by formation of covalent or hydrogen bonds. Spectrophotometric analysis showed that hydroxycinnamic acids can interact stronger with gluten proteins compared to hydroxybenzoic acids.

Zein enhanced the digestive stability of five citrus flavonoids via different binding interaction

BACKGROUND

Zein is commonly used to construct food flavonoid delivery systems. This study investigated the effect and mechanism of zein on the digestive stability of five citrus flavonoids, namely hesperetin (HET), hesperidin (HED), neohesperidin (NHD), naringenin (NEN), and naringin (NIN).

RESULTS

Zein enhanced the digestive stability of the five citrus flavonoids, especially that of HET and NEN, during digestion in the stomach and small intestine. Fluorescence spectroscopy results suggested that citrus flavonoids spontaneously quenched the endogenous fluorescence of zein in static quenching mode. The binding of HET, HED and NHD to zein was driven respectively by electrostatic, hydrophobic and electrostatic interaction. However, Van der Waals' force and hydrogen (H)-bond interaction represented the primary driving force for binding NEN, and NIN to zein to form complexes. The binding of the five citrus flavonoids to zein also caused a diverse bathochromic shift in ultraviolet absorbance. Analysis using Fourier-transform infrared and Raman spectroscopy revealed that the binding behavior of the five citrus flavonoids had different effects on changes in the secondary structures, disulfide bonds, and tyrosine exposure of zein. The results were also partially verified by molecular dynamic simulation.

CONCLUSIONS

Zein enhanced the digestive stability of the five citrus flavonoids via different binding interactions that was due to the difference in molecular structure of citrus flavonoids. © 2022 Society of Chemical Industry.

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.

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 soybean oil on rheological characteristics of dough under high hydrostatic pressure

In order to improve the stability of dough with soybean oil, this paper explored the effect of soybean oil addition on the rheological characteristics of dough under high hydrostatic pressure. The results showed that, compared with the dough without soybean oil, the β-sheet, disulfide bonds content and gauche-ganche-ganche in the dough increased by 4.23%, 0.85 μmol/g and 4.16% respectively when the dough was added with 6% soybean oil, which improved the degree of cross-linking polymerization of gluten protein and the stability of gluten network. Meanwhile, the dough had the highest elastic modulus and the lowest maximum creep compliance (6.85 Pa^-1 ×10^-4 ), indicating that 6% soybean oil significantly increased the elasticity and hardness of the dough. The results of short-range ordered structure and paste properties showed that with the addition of soybean oil, the ordered structure and paste viscosity decreased with the increase of soybean oil.

Low-sodium salt mediated aggregation behavior of gluten in wheat dough

Reducing sodium in foods has attracted the attention of consumers, it is therefore necessary to explore sodium alternatives (i.e., low-sodium salt). However, the mechanism of low-sodium salt on gluten in dough remains unclear. Effect of low-sodium salt on the aggregation behaviors of gluten in dough was investigated and compared with those with NaCl and KCl in this study. The results showed that low-sodium salt enhanced gluten strength and prolonged gluten aggregation time. Low-sodium salt decreased the content of SDS extractable protein under non-reducing conditions. Low-sodium salt changed the spatial conformation of gluten by reducing β-turn structure and increasing β-sheet structure. Confocal laser scanning microscopy images indicated that low-sodium salt promoted the formation of a larger and dense gluten network. In summary, this study showed that low-sodium salt promoted the aggregation of gluten in dough, and the change of gluten structure explained this aggregation mechanism. Its mode of action was similar to NaCl and KCl, which provided a theoretical basis for the study of sodium substitutes in flour products.

Persimmon tannin unevenly changes the physical properties, morphology, subunits composition and cross-linking types of gliadin and glutenin

To answer which is the key component caused the alterations of gluten in the presence of persimmon tannin (PT), the changes on physical properties, morphology, subunits coposition and cross-linking types of glutenin and gliadin were investigated. The results showed that compared with gliadin, glutenin was more sensitive to PT due to the greater changes in the thermal stability, network structure and aggregation behavior. This might be explained by the remarkable decreases in soluble subunits content, free sulfhydryl groups (SH), disulfide bonds (SS) and free amino groups (-NH₂) cross-linking of glutenin after 8% of PT addition, as well as the varying degree in subunits composition. Therefore, glutenin played a more important role in the changes in the properties and network structure of gluten induced by PT than gliadin. Our work provided a guidance for the incorporation of phenolic compounds in wheat flour-based products.

Impact of celluloses and pectins restrictions on gluten development and water distribution in potato-wheat flour dough

The addition of potato to wheat flour extends the nutritional values of bread. However, the adverse effects mediated by high dietary fiber in potato flour could affect the formation of gluten matrix. The water dynamics and distribution determined by the Low field nuclear magnetic resonance (LF-NMR) demonstrated a competitive water binding of dietary fiber, resulting in the partial dehydration and conformational changes of gluten protein complexes. Besides, the microstructure of the dough characterized by Scanning electron microscope (SEM) suggested that the insoluble cellulose could block the continuity of gluten from the spatial position, thereby negative affecting the mechanical properties of the dough. In our study, addition of cellulase and/or pectinase apparently mitigated the gluten aggregation and dehydration, contributing to the formation and the continuity of the three-dimensional gluten network. As a consequence, the specific volume of the bread was increased by 40.2%, and the hardness was reduced by 64.48%.

Vibrational and fluorescence spectroscopy to study gluten and zein interactions in complex dough systems

The volume-spanning network formed by gluten during breadmaking is crucial in the production of high-quality bakery products. Zein proteins are also capable of forming a protein network under specific conditions. Vibrational (Fourier transform infrared spectroscopy (FTIR) and Raman scattering) and fluorescence spectroscopy are powerful, non-invasive techniques capable of assessing protein structures and interactions. The main objective of this project was to explore the suitability of these techniques to study zein and gluten structures and interactions in complex dough systems. The dough samples were prepared by mixing 20 w/w% of protein (with different proportions of zein and gluten) and 80 w/w% of corn starch. The tyrosine (Tyr) fluorescence emission peak (λ_exc = 280 nm) was still present even in those zein-gluten samples containing the highest gluten concentration and lowest zein concentration. This suggests that the Tyr moieties (stemming from zein) are not in close proximity to tryptophan (Trp) of gluten and their fluorescence is not quenched efficiently. Raman scattering results also showed the presence of different Tyr residues, exposed and buried, as well as different conformations of disulfide bridges, in zein and gluten samples. Based on the results from spectroscopic measurements and scanning electron microscopy (SEM), two distinct network structures composed of gluten and zein were identified in the mixed dough systems. The present work illustrates how complementary vibrational (Raman scattering and FTIR) and fluorescence spectroscopy methods can be combined to non-invasively assess protein structure and interactions in a complex food matrix.

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Exploration of non-invasive techniques to study proteins in complex food systems.

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Complementary information obtained on protein structure at several length scales.

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Zein dough viscoelasticity relates to the formation of beta-sheet rich fibrils.

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Gluten and zein form two distinct network structures in dough making.

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Zein inclusion increases water availability for gluten in gluten-zein dough.

Role of Hydrocolloids in the Structure, Cooking, and Nutritional Properties of Fiber-Enriched, Fresh Egg Pasta Based on Tiger Nut Flour and Durum Wheat Semolina

The aim of this work concerns the manufacturing process of fresh egg tagliatelle labeled as a "source of fiber" based on tiger nut flour and wheat semolina. An attempt to improve the quality attributes and cooking properties of the obtained product was made by means of structuring agents. More specifically, a combination of three hydrocolloids (carboximethylcellulose, CMC; xanthan gum, XG; and locust bean gum, LBG) was tested. A Box-Behnken design with randomized response surface methodology was used to determine a suitable combination of these gums to achieve fewer cooking losses, higher water gain and swelling index values, and better texture characteristics before and after cooking. Positive effects on textural characteristics were observed when incorporating XG into the pasta formulation. Cooking and fiber loss also significantly diminished with the XG-CMC combination over 0.8%. No significant effect was found for the other evaluated parameters. A synergistic interaction between LBG and XG was only significant for the water absorption index. The cooked pasta was considered a source of fiber in all cases.

FT-Raman Spectroscopy as a Tool to Study the Secondary Structures of Wheat Gliadin Proteins

Raman spectroscopy is a useful method in biological, biomedical, food, and agricultural studies, allowing the simultaneous examination of various chemical compounds and evaluation of molecular changes occurring in tested objects. The purpose of our research was to explain how the elimination of ω-fractions from the wheat gliadin complex influences the secondary structures of the remaining αβγ-gliadins. To this aim, we analyzed the endosperm of wheat kernels as well as gliadin proteins extracted from two winter wheat genotypes: wasko.gl+ (control genotype containing the full set of gliadins) and wasko.gl− (modified genotype lacking all ω-gliadins). Based on the decomposition of the amide I band, we observed a moderate increase in β-forms (sheets and turns) at the expense of α-helical and random coil structures for gliadins isolated from the flour of the wasko.gl− line. Since ω-gliadins contain no cysteine residues, they do not participate in the formation of the disulfide bridges that stabilize the protein structure. However, they can interact with other proteins via weak, low-energetic hydrogen bonds. We conclude that the elimination of ω-fractions from the gliadin complex causes minor modifications in secondary structures of the remaining gliadin proteins. In our opinion, these small, structural changes of proteins may lead to alterations in gliadin allergenicity.

Non-thermal emerging technologies as alternatives to chemical additives to improve the quality of wheat flour for breadmaking: a review

Wheat flour is the main ingredient used in the preparation of bread. Factors such as low gluten content and the addition of nontraditional ingredients in baking affect the quality of wheat flour and may limit its use in baking. With the increasing trend of "clean label" products, it may be interesting to develop and use physical processes to improve the quality of wheat flour and avoid the use of chemical additives. High hydrostatic pressure, non-thermal plasma, ultrasound, ozonation, ultraviolet light, and pulsed light treatments are non-thermal emerging technologies (NTETs) that have been studied for this purpose. They were originally developed to inactivate microorganisms and enzymes in foods. Additionally, these technologies can be used at low temperatures to modify the most important component of wheat flour, i.e., gluten and its fractions, which are responsible for the rheological properties of wheat flour dough. Thus, this review focuses on the effects of these NTETs by considering the following factors: (1) the technological properties of gluten, (2) gluten-starch interactions, (3) possible effects of NTETs on minor components of flours, and (4) the quality of wheat flour and the resulting final products.

Glutathione-mediated formation of disulfide bonds modulates the properties of myofibrillar protein gels at different temperatures

The present study illustrated modulation of protein aggregation by affecting disulfide/sulfhydryl exchange reactions by adding different concentrations of free thiol represented by reduced-glutathione (GSH) for modulating myofibrillar protein (MP) gel properties at 75 °C or 95 °C. Gel strength and rheological results showed the effects of GSH were dependent on the concentrations (5, 10, 20, 40, and 80 g/kg) and heating temperatures. SEM results showed that the addition of GSH improved the gel microstructure at 95 °C. AFM and DLS results indicated that protein aggregation was also inhibited. At 75 °C, the addition of GSH influenced both MP aggregation and gel properties. Low concentrations (5, 10 g/kg) of GSH promoted aggregation, whereas high concentrations (20, 40, and 80 g/kg) of GSH inhibited this. By analyzing the protein structure and cross-linking pattern changes of MP and MP/GSH composites, a pathway involving GSH influencing MP gel properties was determined.