Impact of oligomeric procyanidins on wheat gluten microstructure and physicochemical properties

Carboxymethyl Chitosan-Based Antioxidant Hydrogel Accelerates Diabetic Wound Healing

Diabetic wound healing is hampered due to oxidative stress, exacerbated inflammation, and impaired angiogenesis in the wounds. A pH-sensitive antioxidant hydrogel based on carboxymethyl chitosan (CMCS), oligoprocyanidins (OPC), and oxide dextran (Oxd) is prepared to accelerate diabetic wound healing. The hydrogel network is formed via imine and hydrogen bonding interactions in the presence of hydroxyl, amino, and aldehyde groups, and deferoxamine (DFO) is incorporated into the hydrogel. The hydrogel shows pH-triggered drug release, a good antioxidant, and anti-inflammatory properties, and can promote tube formation and cell migration in vitro. Moreover, the hydrogel can accelerate wound healing in streptozotocin (STZ)-induced diabetic mice by regulating the inflammation environment with up-regulation of anti-inflammatory factors (IL-4 and IL-10) and down-regulation of pro-inflammatory factors (TNF-α and IL-6), and promoting angiogenesis with up-regulation of HIF-1α, VEGF, and CD31. Thus, the pH-sensitive antioxidant hydrogel provides a promising therapeutic strategy for diabetic wound healing.

Effects of Low-Allergen Wheat and Bayberry Leaf on Wheat Bread: A Comparison with Commercial Wheat

Gliadin and glutenin wheat proteins are major food allergens. The allergenicity of various wheat products, such as bread, can be reduced by substituting flour with plant-derived tannins. Here, we investigated a technique for reducing the allergenicity of wheat by utilizing the properties of proanthocyanidins (PAs), which strongly bind to proteins. We compared commercial bread wheat (BW), low-allergen wheat (1BS-18 "Minamino Kaori"; 1BS-18M), and bayberry leaves (BBLs). Allergenicity was investigated through enzyme-linked immunosorbent assays (ELISAs) and Western blotting (WB). The immunoreactivity of wheat allergens in both BW and 1BS-18M decreased in a concentration-dependent manner with BBL substitution, and the effect was greatest at 10%. The antioxidative properties also increased with BBL substitution, and the highest antioxidative property was observed at 10%. The specific volumes of both BW and 1BS-18M decreased while the a* value (green to red) increased with increasing BBL substitution. In contrast, no significant differences were observed in the texture of breads with 0% (control), 3%, or 5% BBL substitution. However, 10% BBL substitution led to a significant (p < 0.05) reduction in the texture of the bread. Therefore, 5% BBL substitution is optimal for achieving low allergenicity and improved antioxidative properties while maintaining quality.

Moderate regulation of wheat B-starch ratio: Improvement of molecular structure, spatial conformation, aggregation behavior of reconstituted fermented doughs and its processing suitability

Aiming to investigate the changes and effects of different particle sizes of wheat A/B starch during dough fermentation, the present study reconstituted A/B starch fractions in ratios of 100:0, 75:25, 50:50, 25:75, and 0:100, further blended with gluten and subjected to slight (20 min), medium (30 min), and high (60 min) fermentation processes by yeasts. Results showed that fermentation gas production promoted gluten network extension, inducing starch granule exposure and dough surface roughness. Also, fermentation fractured protein intermolecular disulfide bonds and decreased α-helix and β-folded structure content, contributing to GMP, LPP, and SPP content decreases. Moreover, moderately increasing the B-starch ratio in the dough can improve gluten network stability, continuity, and air-holding capacity. The 25A-75B steam bread exhibited optimal processing suitability (better morphology, texture, and quality) due to its higher GMP and polymer protein content with lower free sulfhydryl and monomeric protein content. Further, conformational relationships indicated the key indicators influencing dough products' properties were free sulfhydryl content, GMP content, protein molecular weight distribution, and secondary structure. The obtained findings contributed to understanding the effect of wheat starch granule size distribution on dough processing behavior, and future targeted breeding for wheat cultivars with high B-starch content for improved fermentation pasta product qualities.

Adequately increasing the wheat B-starch ratio can improve the structure-properties of dough during freeze-thaw cycles: Mechanisms and conformational relations

To reveal the influence of wheat starch particle size distribution on frozen dough quality, this study reconstituted A/B starch according to 100:0, 75:25, 50:50, 25:75 and 0:100 and prepared reconstituted dough by compounding with gluten proteins. Further, the freeze-thaw cycle of 1, 3, and 9 times for reconstituted dough was performed to investigate its ratio-regulatory role of A- and B-starch. The results showed that the freeze-thaw cycle induced gluten network breakage and starch granule exposure in doughs mainly by disrupting disulfide and hydrogen bonds between gluten protein molecules and upsetting their secondary structures, leading to a reduction in GMP and polymer protein content and an increase in freezing water content. Moreover, a moderate increase (25-50 %) in the B-starch proportion can minimize gluten protein deterioration by freeze-thaw cycles. However, excessive B-starch amounts (75-100 %) can also adversely affect gluten structure. The prepared dumpling wrappers under the 50A-50B ratio showed optimal steaming loss rate, hardness, and chewiness during the freeze-thaw cycle. Correlation analysis indicated that the B-starch ratio and its filling pattern improved dough freeze-thaw deterioration primarily by affecting dough-free sulfhydryl content, protein molecular weight distribution, secondary structure, and ΔH. The results may provide insights and guidelines for product development and storage for frozen pasta.

Structural modification of starch and protein: From the perspective of gelatinization degree of oat flour

To clarify the relationship between gelatinization degree and structure characteristics, oat kernels were roasted to different gelatinization degree of 15 %-90 % based on tempering water content of 22.5 %-35 %, and the structure characteristics of starch and protein were evaluated. The results showed that the increased gelatinization degree dependent on tempering water content promoted protein aggregation on the surface of starch particles, forming larger aggregates with molecular weight >100 kDa. Oat kernels presented a dense starch gel network structure induced by gelatinized starch. Partial gelatinization of starch led to a decrease in pasting viscosities (setback viscosity, 3.91 Pa·s-1.59 Pa·s) and enthalpy (5.12 J/g-0.11 J/g). With the increase of gelatinization degree, the starch crystal structure conversed from A + V type to V type, accompanied by the formation of starch-lipid complexes and a decrease of relative crystallinity (22.28 %-8.72 %). Moreover, 50 % gelatinized oat flour possessed the highest β-sheet structure (38.04 %), but a decrease in surface hydrophobicity and an increase in endogenous fluorescence intensity were found in oat flour of gelatinization degree >50 %. This study provided a theoretical reference for the application of oat flour with different gelatinization degrees to match suitable products.

Effects of the Roasting-Assisted Aqueous Ethanol Extraction of Peanut Oil on the Structure and Functional Properties of Dreg Proteins

The effects of the roasting-assisted aqueous ethanol extraction of peanut oil on the structure and functional properties of dreg proteins were investigated to interpret the high free oil yield and provide a basis for the full utilization of peanut protein resources. The roasting-assisted aqueous ethanol extraction of peanut oil obtained a free oil yield of 97.74% and a protein retention rate of 75.80% in the dreg. The water-holding capacity of dreg proteins increased significantly, and the oil-holding capacity and surface hydrophobicity decreased significantly, reducing the binding ability with oil and thus facilitating the release of oil. Although the relative crystallinity and denaturation enthalpy of the dreg proteins decreased slightly, the denaturation temperatures remained unchanged. Infrared and Raman spectra identified decreases in the C-H stretching vibration, Fermi resonance and α-helix, and increases in random coil, β-sheet and β-turn, showing a slight decrease in the overall ordering of proteins. After the roasting treatment, 62.57-135.33% of the protein functional properties were still preserved. Therefore, the roasting-assisted aqueous ethanol extraction of peanut oil is beneficial for fully utilizing the oil and protein resources in peanuts.

Lima bean (Phaseolus lunatus Linn.) protein isolate as a promising plant protein mixed with xanthan gum for stabilizing oil-in-water emulsions

BACKGROUND

Lima bean protein isolate (LPI) is an underutilized plant protein. Similar to other plant proteins, it may display poor emulsification properties. In order to improve its emulsifying properties, one effective approach is using protein and polysaccharide mixtures. This work investigated the structural and emulsifying properties of LPI as well as the development of an LPI/xanthan gum (XG)-stabilized oil-in-water emulsion.

RESULTS

The highest protein solubility (84.14%) of LPI was observed and the molecular weights (Mw ) of most LPI subunits were less than 35 kDa. The enhanced emulsifying activity index (15.97 m2  g-1 ) of LPI might be associated with its relatively high protein solubility and more low-Mw subunits (Mw  < 35 kDa). The effects of oil volume fraction (ϕ) on droplet size, microstructure, rheological behavior and stability of emulsions were investigated. As ϕ increased from 0.2 to 0.8, the emulsion was arranged from spherical and dispersed oil droplets to polyhedral packing of oil droplets adjacent to each other, while the LPI/XG mixtures changed from particles (in the uncrowded interfacial layer) to lamellae (in the crowded interfacial layer). When ϕ was 0.6, the emulsion was in a transitional state with the coexistence of particles and lamellar structures on the oil droplet surface. The LPI/XG-stabilized emulsions with ϕ values of 0.6-0.8 showed the highest stability during a 14-day storage period.

CONCLUSION

This study developed a promising plant-based protein resource, LPI, and demonstrates potential application of LPI/XG as an emulsifying stabilizer in foods. © 2023 Society of Chemical Industry.

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.

Plant-Based Protein-Phenolic Interactions: Effect on different matrices and in vitro gastrointestinal digestion

This review summarizes the literature on the interaction between plant-based proteins and phenolics. The structure of the phenolic compound, the plant source of proteins, matrix properties (pH, temperature), and interaction mechanism (covalent and non-covalent) change the secondary structure, ζ-potential, surface hydrophobicity, and thermal stability of proteins as well as their functional properties including solubility, foaming, and emulsifying properties. Studies indicated that the foaming and emulsifying properties may be affected either positively or negatively according to the type and concentration of the phenolic compound. Protein digestibility, on the other hand, differs depending on (1) the phenolic concentration, (2) whether the food matrix is ​​solid or liquid, and (3) the state of the food-whether it is heat-treated or prepared as a mixture without heat treatment in the presence of phenolics. This review comprehensively covers the effects of protein-phenolic interactions on the structure and properties of proteins, including functional properties and digestibility both in model systems and real food matrix.

Effect of proanthocyanidins from different sources on the digestibility, physicochemical properties and structure of gelatinized maize starch

The effect of proanthocyanidins (PAs) from Chinese bayberry leaves (BLPs), grape seeds (GSPs), peanut skins (PSPs) and pine barks (PBPs) on physicochemical properties, structure and in-vitro digestibility of gelatinized maize starch was investigated. The results showed that all PAs remarkably retarded starch digestibility, meanwhile, BLPs highlighted superiority in increasing resistant starch content from 31.29 ± 1.12 % to 68.61 ± 1.15 %. The iodine-binding affinity analysis confirmed the interaction between PAs and starch, especially the stronger binding of BLPs to amylose, which was driven by non-covalent bonds supported by XRD and FT-IR analysis. Further, we found that PAs altered the rheological properties, thermal properties and morphology structure of starch. In brief, PAs induced larger consistency, poorer flow ability, lower gelatinization temperatures and melting enthalpy change (ΔH) of starch paste. SEM and CLSM observation demonstrated that PAs facilitated starch aggregation. Our results indicated that PAs especially BLPs could be considered as potential additives to modify starch in food industry.

The Impact of AAPH-Induced Oxidation on the Functional and Structural Properties, and Proteomics of Arachin

The aim of this study was to investigate the effect of 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH)-induced oxidation on the functional, structural properties and proteomic information of arachin. The results showed that moderate oxidation improved the water/oil holding capacity of proteins and increased the emulsifying stability, while excessive oxidation increased the carbonyl content, reduced the thiol content, altered the structure and thermal stability, and reduced most of the physicochemical properties. Through LC-QE-MS analysis, it was observed that oxidation leads to various modifications in arachin, including carbamylation, oxidation, and reduction, among others. In addition, 15 differentially expressed proteins were identified. Through gene ontology (GO) analysis, these proteins primarily affected the cellular and metabolic processes in the biological process category. Further Kyoto encyclopedia of genes and genomes (KEGG) analysis revealed that the "proteasome; protein processing in the endoplasmic reticulum (PPER)" pathway was the most significantly enriched signaling pathway during the oxidation process of arachin. In conclusion, this study demonstrated that AAPH-induced oxidation can alter the conformation and proteome of arachin, thereby affecting its corresponding functional properties. The findings of this study can potentially serve as a theoretical basis and foundational reference for the management of peanut processing and storage.

Effect of grape seed proanthocyanidin on the structural and physicochemical properties of bread during bread fermentation stage

Bread was prepared using wheat flour with grape seed proanthocyanidin (GSP) (0.4%). GSP improved the textural properties of bread including hardness, cohesiviness, gumminess and chewiness. At the last stage of fermentation, GSP reinforced the gluten microstructure with increased the disulfide bonds and hydrophobic interaction and α-helix in the secondary structures. Moreover, GSP addition could increase the total phenolics and antioxidative acitivity of the bread significantly. In addition, the degree of fermentation had a strong influence on the dough forces, and the reasonable control of bread fermentation time was beneficial to improve the bread quality, which provided a reference for the bread processing industry.

Improving the Microstructural and Rheological Properties of Frozen Unfermented Wheat Dough with Laccase and Ferulic Acid

The quality deterioration that is induced by freezing treatment limits the development of frozen dough technology for standardized and delayed baking. In this study, laccase (LAC) and ferulic acid (FA) were employed to improve the rheological properties and microstructure of frozen unfermented dough. The results showed that the dough with LAC + FA had a lower softening degree than the dough with FA alone. Correspondingly, LAC + FA incorporation enhanced the viscoelastic behavior of frozen unfermented dough with better stability. Furthermore, a more uniform and homogeneous gluten network was observed in the LAC + FA-supplemented dough after 21 d of storage. The structural stability of the frozen gluten sample increased after LAC + FA treatment, possibly owing to an increase in the oxidation degree of FA. Moreover, LAC + FA treatment promoted the oxidation of the sulfhydryl groups to some extent, resulting in more extensive cross-linking. LAC + FA treatment hindered the protein conformational changes typically induced by frozen storage compared with LAC alone. Overall, LAC + FA treatment has a synergistic effect on enhancing the viscoelastic behaviors of frozen unfermented dough and inhibiting the conformational variation in frozen gluten; thus, it shows promise for improving frozen dough.

The additive interactions between high-molecular-weight glutenin subunits and tannic acid improve the wheat quality

Wheat gluten proteins, especially high-molecular-weight glutenin subunits (HMW-GS), are the main contributor to flour processing quality. Tannic acid (TA) consisting of a central glucose unit and ten gallic acid molecules is a phenolic acid that improves the processing quality. However, the underlying mechanism of TA's improvement remains largely unknown. Here, we showed that TA's improving effects on gluten aggregation, dough-mixing and bread-making properties were directly associated with the kinds of HMW-GS expressed in wheat seeds in HMW-GS near-isogenic lines (NILs). We established a biochemical framework, elucidated the additive effects of HMW-GS-TA interaction and discovered that TA cross-linked specifically with wheat glutenins but not gliadins, and reduced gluten surface hydrophobicity and SH content depending on the kinds of expressed HMW-GS in the wheat seeds. We also demonstrated that hydrogen bonds play an essential role in TA-HMW-GS interactions and improvement of wheat processing quality. Additionally, the effects of TA on the antioxidant capacity and on nutrient (protein and starch) digestibility were also investigated in the NILs of HMW-GS. TA increased antioxidant capacity but did not affect the digestion of starches and proteins. Our results revealed that TA more effectively strengthened wheat gluten in the presence of more HMW-GS kinds, highlighting TA's potential as an improver toward healthy and quality bread and demonstrating that manipulating hydrogen bonds was a previously overlooked approach to improve wheat quality.

Effect of extrusion parameters on the interaction between rice starch and glutelin in the preparation of reconstituted rice

Reconstituted rice produced by extrusion has been attracted attention due to nutritional fortification and convenient production. Nevertheless, how to achieve desirable qualities and physicochemical properties of reconstituted rice nearly to natural rice by regulating extrusion process parameters is difficult. Herein, rice starch/glutelin mixture as raw material of reconstituted rice was extruded at varying extrusion conditions. Specific mechanical energy (SME) and sectional expansion index (SEI) dropped with rise in density (R² = 0.9117 and 0.8207). Solubility was enhanced with increase in product temperature (R² = 0.9085), color darkened and shifted to reddish and yellowish as extrusion temperature increased (R² = 0.8577). These trends were well fitted by sigmoid models. Furthermore, SME enhanced hydrophobic and electrostatic interactions between rice starch and glutelin and caused the reduction in crystallinity and thermal stability, promoting the formation of a bi-continuous matrix of protein aggregates with rice starch. The obtained results can be applied to guide the production of reconstituted rice with desirable qualities.

Effect of Tea Polyphenols on the Storage Stability of Non-Fermented Frozen Dough: Protein Structures and State of Water

The usage of tea polyphenols (TPs) as a natural food additive into non-fermented frozen dough (NFFD) has rarely been investigated, and results have been controversial. Hence, this study investigated the effect of TPs at various levels (0, 0.5, 1, and 2%) on the quality of NFFD stored from 0 to 4 weeks. The rheological characteristics, water state, protein, and its microstructure were analyzed by DSC, LF-NMR, SDS-PAGE, FT-IR, and SEM, respectively. Results showed that the 0.5% TP group delayed the deterioration of protein and inhibited the water migration in dough throughout the whole frozen storage period. In addition, the 0.5% TP group enhanced the rheological properties of NFFD and stabilized the sulfhydryl content and the secondary structure in the gluten network. On the contrary, opposite phenomena were found in the 1 and 2% TP groups, which might be due to the induction of excess hydroxyl groups from TPs. In conclusion, our results suggested that a proper addition of TPs, but not an excessive amount (>1%), exhibited beneficial effects in maintaining the quality of NFFD during the 4-week frozen storage. Moreover, this paper elucidated the mechanism of TPs in influencing the protein structure and water state of NFFD during storage and provided new insight into its application in dough-based foods.

A combined approach for modifying pea protein isolate to greatly improve its solubility and emulsifying stability

Pea protein-based delivery systems have drawn much attention in the food and pharmaceutical fields in recent years. However, its broad application faces great limitations because of the low solubility. Here, we present a novel and effective approach to overcome this difficulty and enhance the techno-functional characteristics, especially emulsifying stability, of the pea protein isolate (PPI). By combining pH-shifting with ultrasound and heating (PUH), we concluded that the solubility of PPI greatly increased from 29.5 % to 90.4 %, whereas its surface hydrophobicity increased from 1098 to 3706. This was accompanied by the changes of PPI structure, as shown by circular dichroism and scanning electron microscopy. In addition, the modified PPI was applied to stabilize sunflower oil-in-water emulsions. The droplet size of the emulsion with PUHP was reduced and its emulsion stability was significantly elevated. Taken together, we propose a novel combined approach to prepare modified PPI with high solubility and emulsion stability. We expect our method will have a wider application in modifying plant proteins and improving their industrial processing.

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.

Liquid metal-tailored gluten network for protein-based e-skin

Designing electronic skin (e-skin) with proteins is a critical way to endow e-skin with biocompatibility, but engineering protein structures to achieve controllable mechanical properties and self-healing ability remains a challenge. Here, we develop a hybrid gluten network through the incorporation of a eutectic gallium indium alloy (EGaIn) to design a self-healable e-skin with improved mechanical properties. The intrinsic reversible disulfide bond/sulfhydryl group reconfiguration of gluten networks is explored as a driving force to introduce EGaIn as a chemical cross-linker, thus inducing secondary structure rearrangement of gluten to form additional β-sheets as physical cross-linkers. Remarkably, the obtained gluten-based material is self-healing, achieves synthetic material-like stretchability (>1600%) and possesses the ability to promote skin cell proliferation. The final e-skin is biocompatible and biodegradable and can sense strain changes from human motions of different scales. The protein network microregulation method paves the way for future skin-like protein-based e-skin.

E-skins currently suffer from issues to do with the predominantly non-biological materials they are made from. Here, the authors report on a gluten network which is cross-linked with EGaIn liquid metal to make a self-healing, biocompatible, biodegradable, stretchable and conductive material which is demonstrated as a movement strain sensor.

The dough-strengthening and spore-sterilizing effects of mannosylerythritol lipid-A in frozen dough and its application in bread making

Biosurfactants have been put into applications in breadmaking industry, while the effects of mannosylerythritol lipid-A (MEL-A) on gluten network of frozen dough, bread quality and microbial spoilage were firstly investigated in this study. Rheology and differential scanning calorimetry (DSC) analysis showed that MEL-A significantly improved the rheological properties of frozen dough and reduced the content of frozen water. Further experiments showed that MEL-A promoted the formation of aggregates by interacting with gluten protein, and strengthened the gluten network through molecular weight distribution measurement and microstructure observation, effectively avoiding the destruction of ice crystals. A series of bread assessments illustrated MEL-A improved the loaf volume, gas retention ability and textural property. In addition, MEL-A (1.5%) killed 99.97% of the vegetative cells of Bacillus cereus and 75.54% of the spores, and at the same time had a slight inactivation effect on yeast. These results indicate that MEL-A has broad application prospects in the baking industry and the storage stage of flour products.

Changes of aggregation and structural properties of heat-denatured gluten proteins in fast-frozen steamed bread during frozen storage

The aim of this research was to clearly clarify the deterioration mechanism of heat-denatured gluten proteins by exploring the change of aggregation and structural characteristics of heat-denatured gluten proteins in the steamed bread system and the steamed gluten system during frozen storage. An increase in the total SDS-soluble protein content was determined, which mainly attributed to the soluble monomer protein content increased. Combined with the significant increase of free sulfhydryl, from 3.12 μmol/g to 5.06 μmol/g and 2.64 μmol/g to 3.29 μmol/g, respectively, it can be inferred that the proteins depolymerization induced by frozen storage was mainly involved in the breakdown of heat-induced glutenin-gliadin disulfide cross-linking. Frozen storage induced the conversion of random coil structure to β-sheet structure and a ruptured microstructure with small fragment was observed. Moreover, the protein of steamed bread system was easier to depolymerize than that of the steamed gluten system.

Impact of condensed tannin interactions with grain proteins and non-starch polysaccharides on batter system properties

Proanthocyanidins (PA) cross-link wheat gluten proteins and dramatically enhance batter viscosity; PA could similarly affect related grains. This study aimed to determine PA effect on viscosity and pasting properties of barley, rye, and oat flours, and the relative contributions of PA interactions with proteins and non-starch polysaccharides (NSP). PA significantly increased batter viscosity, stability, and RVA peak viscosity in rye and barley flours (2.8× and 1.2×, respectively). Interestingly, viscosity peaked distinctively ~75 °C in PA-treated rye and barley flours, and their isolated protein-starch systems, indicating prolamins unravelled and complexed with PA during heating. Oat was largely unaffected by PA, likely because of its protein composition. Furthermore, water-soluble rye NSP and arabinoxylans, but not barley β-glucans, significantly increased starch pasting viscosity with PA; oxidative gelation was not a factor. Thus, rye flour viscosity dramatically increased through interactive effects of PA on rye proteins and NSP, which could expand its food applications.

Combined effects of quercetin and sodium chloride concentrations on wheat gliadin structure and physicochemical properties

BACKGROUND

Polyphenols may interact with protein via covalent bonds and non-covalent interactions, improving the structures and functional properties of the protein. The cross-linking between the polyphenol and protein is susceptible to salt (sodium chloride, NaCl) concentrations. Our study investigated the combined effects of quercetin (Q) and NaCl concentrations on wheat gliadin (G) structure and physicochemical properties.

RESULTS

Q and NaCl addition resulted in a more compact protein microstructure. The improved foaming and emulsifying properties indicated that the modified G might be potent as a novel surface-active agent. Differential scanning calorimetry analysis indicated that Q protected the thermal stability from destruction at 50 and 200 mmol L^-1 NaCl concentrations, with narrower protein denaturation peaks. Fourier transform infrared and the Raman spectral analyses showed the secondary structural and microenvironmental changes of G. NaCl addition imparted a rearrangement of hydrogen bonds in the polypeptide chain and the disorder of protein structure, whereas Q enhanced the transition from β-sheets and random coils to α-helices and β-turns, forming a more ordered structure. Moreover, the interaction between G and Q resulted in significant disulfide bridges conformational rearrangements in the protein.

CONCLUSION

The results showed the benefits of natural food additives in food processing, which might have potential in improving the structure and physicochemical properties of protein-based foods. © 2020 Society of Chemical Industry.

Production of self-assembling acylated ovalbumin nanogels as stable delivery vehicles for curcumin

In this study, we evaluated potential usage of acylated ovalbumin (AOVA) nanogels fabricated via acylation modification and heat-induced self-assembly process as novel delivery systems for curcumin. Compared to native ovalbumin (NOVA) nanogels without chemical acylation, the obtained AOVA nanogels have shown smaller average hydrodynamic diameter (155.73 nm), relatively uniform size distribution (polydispersity index around 0.28), enhanced negative surface charge (-24.3 mV), and an improved stability under the conditions of high ionic strength, different pH and storage time. Moreover, AOVA nanogels exhibited a remarkable conformational change in secondary and tertiary structures, improved surface hydrophobicity, and increased free sulfhydryl content compared with NOVA nanogels. Moreover, curcumin encapsulated in AOVA nanogels displayed higher encapsulation efficiency (93.64%) and slower sustained release under simulated gastrointestinal conditions as compared with NOVA nanogels. Hence, we have suggested that AOVA nanogels successfully fabricated with improved physicochemical properties as a novel ideal carrier for hydrophobic active compounds.

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.

Oligomeric procyanidins inhibit insulin fibrillation by forming unstructured and off-pathway aggregates

Effects of natural polyphenols on insulin fibrillation were compared. OPCs show potent inhibitory effects at all stages of insulin fibrillation and redirect the insulin aggregation pathway via the formation of unstructured, off-pathway aggregates.

Interactions between gluten and water-unextractable arabinoxylan during the thermal treatment

This study aimed to investigate the interactions between gluten and water-unextractable arabinoxylan (WUAX), which changed the conformation and aggregation of gluten during the thermal treatment. In this work, the interactions between water-unextractable arabinoxylan and wheat gluten during thermal treatment were extensively evaluated by different techniques. The results showed that the extra WUAX could impair the viscoelasticity as well as weaken the thermal properties of gluten. The fluorescence spectra revealed the extra WUAX changed the conformation of gluten molecules. Besides, chemical interaction measurement indicated that the extra WUAX prevented the formation of partial disulfide bonds and had a major effect on the hydrophobic interaction of gluten. In summary, these results indicated that WUAX disrupted the covalent crosslinking by affecting disulfide bonds between gluten proteins, and dominated the folding/unfolding process of gluten via the competition with gluten for water, resulting in the poor quality of whole wheat-based foods.

Effect of steam explosion on nutritional composition and antioxidative activities of okra seed and its application in gluten-free cookies

Health-conscious consumers are increasingly interested in gluten-free (GF) foods. Raw okra seed (ROS) flour and steam-exploded okra seed (SEOS) flour were explored for developing GF cookies with high nutritional values and in vitro enzymatic digestion. Results indicated that the steam explosion exhibited significant effects on enhancing the release of dietary fibers and lipids in okra seed flour at moderate explosion pressure. Although steam explosion caused the loss of flavonoid compounds, moderate high explosion pressure enhanced the release of total phenolics ranged from 294.57 to 619.07 mg GAE/100 g DM with significantly improved DPPH• radical scavenging activity (from 18.78% to 67.34%) and ferric reducing antioxidant power (from 13.37% to 149.04%). The rapidly digestible starch (RDS) content in GF cookies decreased with increasing steam explosion severity, whereas slowly digestible starch (SDS) and resistant starch (RS) contents significantly increased from 36.91% to 40.92% and from 2.50% to 9.06%, respectively. Steam explosion is an effective technique for enhancing the release of nutrients like dietary fiber and total phenolics, and okra seed flour, especially SEOS flour, can be alternative choices to provide food functional materials for developing various GF food products.

Persimmon tannin changes the properties and the morphology of wheat gluten by altering the cross-linking, and the secondary structure in a dose-dependent manner

The effects of persimmon tannin (PT) on the texture, viscoelasticity, thermal stability, and morphology of gluten were studied and the underlying mechanisms were also explored. The results showed that PT increased the hardness and viscoelasticity but lowered the cohesiveness and extensibility of gluten in a dose-dependent manner. Additionally, PT increased the denaturation temperature and enthalpy of gluten, and induced the formation of gluten with compact structure. High concentration of PT (8%) significantly increased the hardness and viscoelasticity of gluten, and induced the formation of compact structure of gluten by disturbing the conformation of gluten, and interfering gluten cross-linking through decreasing disulfide bonds, free sulfydryl groups, and free amino groups. In contrast, low concentration (0.25%) of PT slightly altered the gluten properties and morphology. Our work extended the study on the supplementation of phenolic compounds in wheat flour-based products.

Effects of edible plant polyphenols on gluten protein functionality and potential applications of polyphenol-gluten interactions

Expanding plant-based protein applications is increasingly popular. Polyphenol interactions with wheat gluten proteins can be exploited to create novel functional foods and food ingredients. Polyphenols are antioxidants, thus generally decrease gluten strength by reducing disulfide cross-linking. Monomeric polyphenols can be used to reduce dough mix time and improve flexibility of the gluten network, including to plasticize gluten films. However, high-molecular-weight polyphenols (tannins) cross-link gluten proteins, thereby increasing protein network density and strength. Tannin-gluten interactions can greatly increase gluten tensile strength in dough matrices, as well as batter viscosity and stability. This could be leveraged to reduce detrimental effects of healthful inclusions, like bran and fiber, to loaf breads and other wheat-based products. Further, the dual functions of tannins as an antioxidant and gluten cross-linker could help restructure gluten proteins and improve the texture of plant-based meat alternatives. Tannin-gluten interactions may also be used to reduce inflammatory effects of gluten experienced by those with gluten allergies and celiac disease. Other potential applications of tannin-gluten interactions include formation of food matrices to reduce starch digestibility; creation of novel biomaterials for edible films or medical second skin type bandages; or targeted distribution of micronutrients in the digestive tract. This review focuses on the effects of polyphenols on wheat gluten functionality and discusses emerging opportunities to employ polyphenol-gluten interactions.

Interaction between wheat gliadin and quercetin under different pH conditions analyzed by multi-spectroscopy methods

Polyphenols have been known to have significant binding affinity for proteins, and the specific condition (such as pH) could affect the degree of binding, the formation of covalent bond, and non-covalent interaction. In this study, characteristics of binding quercetin (Q) to wheat gliadin (G) which is a strong food allergen, were studied from pH 2.0 to pH 9.0. The results showed that Q quenched the fluorescence intensity of G by dynamic and static quenching modes and the stoichiometry of binding was close to 1. Intermolecular binding distances were smaller than 8 nm. Thermodynamic parameters suggested that hydrophobic force took charge of the formation of complexes at pH 2.0-4.0, whereas hydrogen bonds and van der Waals forces at pH 5.0-9.0. Analyses of the Fourier transform infrared and the Raman spectra along with synchronous fluorescence spectra revealed secondary and tertiary structural alterations and microenvironmental changed around protein fluorophores upon complexation with Q. The gauche-gauche-trans conformation increased at the expenses of the gauche-gauche-gauche conformation and the transition from β-turn and random coil to α-helix and β-sheet at pH 5.0 might decrease the allergenicity of G. These results provided new insights into G/Q interactions at different pH values, which may have potentials in decreasing allergen immunoreactivity.

Development of Self-Healing Double-Network Hydrogels: Enhancement of the Strength of Wheat Gluten Hydrogels by In Situ Metal-Catechol Coordination

Wheat gluten, a byproduct of the wheat starch industry, is widely used as a dough strengthener and gelling agent. In this research, we developed novel double-network hydrogels by gelation of gluten using in situ metal-catechol coordination. The first network consisted of physically associated gluten molecules, while the second network consisted of Fe³⁺-cross-linked proanthocyanidins (PACs). Dynamic shear rheology experiments suggested that coordination of Fe³⁺ and PACs greatly enhanced the mechanical properties of the gluten hydrogels. The double-network hydrogels exhibited a 3-fold higher shear modulus than pure gluten hydrogels. The formation of bis- and tris-catechol-Fe³⁺ complexes between Fe³⁺ and PACs in the hydrogels was confirmed by ultraviolet-visible spectrometry and isothermal titration calorimetry (ITC). The ITC measurements of Fe³⁺ binding to PACs indicated a molar stoichiometry of 1:4 and a dissociation constant ( K_D) of 24.9 × 10^-9. When subject to repeated shear deformation-compression cycles, the hydrogels exhibited strong and rapid recovery of their rheological properties. The strong, self-healing characteristics of the double-network gluten hydrogels produced in this study may be useful for certain applications in the food, agriculture, biomedicine, and tissue-engineering industries.