Aggregation behavior of wheat gluten during carboxylic acid deamidation upon hydrothermal treatment

Effects of purple cabbage anthocyanin extract on the gluten characteristics and the gluten network evolution of high-gluten dough

BACKGROUND

Anthocyanins are polyphenolic pigments that have hypoglycemic, antioxidation, anti-aging, and other effects. Research has shown that polyphenols can optimize the processing of dough and improve the texture and nutritional characteristics of dough products. The formation of gluten networks is decisive for the quality of flour products. The effects of purple cabbage anthocyanin (PCA) extract on the structure, microscopic morphology, and network formation of gluten protein were studied, and the types of cross-linking between PCA and gluten protein are discussed.

RESULTS

The results show that PCA extract increased the free sulfhydryl (SH) group content and the free amino group of gluten proteins, stimulated an increase in the β-sheet ratio and the decrease of α-helix ratio, and increased the gluten index significantly (P < 0.05). The PCA extract also induced gluten protein aggregation, increased the height of protein molecular chains, and stimulated the formation of gluten networks. When PCA extract concentrations were 4 g kg-1 and 8 g kg-1, the gluten network was more homogeneous, continuous, and dense.

CONCLUSION

Appropriate anthocyanins have a positive effect on the properties of gluten and promote the formation of gluten networks. Excessive anthocyanins destroy gluten protein interaction and harm gluten cross-linking. This study may provide a useful source of data for the production of functional flour products rich in anthocyanins. © 2024 Society of Chemical Industry.

Wheat gluten deamidation: structure, allergenicity and its application in hypoallergenic noodles

BACKGROUND

Wheat gluten (WG) containing gliadin and glutenin are considered the main allergens in wheat allergy as a result of their glutamine-rich peptides. Deamidation is a viable and efficient approach for protein modifications converting glutamine into glutamic acid, which may have the potential for allergenicity reduction of WG.

RESULTS

Deamidation by citric acid was performed to investigate the effects on structure, allergenicity and noodle textural properties of wheat gluten (WG). WG was heated at 100 °C in 1 m citric acid to yield deamidated WG with degrees of deamidation (DD) ranging from DWG-25 (25% DD) to DWG-70 (70% DD). Fourier-transform infrared and intrinsic fluorescence spectroscopy results suggested the unfolding of WG structure during deamidation, and sodium dodecyl sulphate-polyacrylamide gel electrophoresis showed molecular weight shifts at the 35-63 kDa region, suggesting that the deamidation mainly occurred on low molecular weight glutenin subunits and γ- gliadin of the WG. An enzyme-linked immunosorbent assay of deamidated WG revealed a decrease in absorbance and immunoblotting indicated that the intensities of protein bands at 35-63 kDa decreased, which suggested that deamidation of WG might have caused a greater loss of epitopes than the generation of new epitopes caused by unfolding of WG, and thereby reduction of the immunodominant immunoglobulin E binding capacity, ultimately leading to the decrease in allergenicity. DWG-25 was used in the preparation of recombinant hypoallergenic noodles, and the hardness, elasticity, chewiness and gumminess were improved significantly by the addition of azodicarbonamide.

CONCLUSION

The present shows the potential for deamidation of the WG products used in novel hypoallergenic food development. © 2023 Society of Chemical Industry.

Citric Acid: Properties, Microbial Production, and Applications in Industries

Citric acid finds broad applications in various industrial sectors, such as the pharmaceutical, food, chemical, and cosmetic industries. The bioproduction of citric acid uses various microorganisms, but the most commonly employed ones are filamentous fungi such as Aspergillus niger and yeast Yarrowia lipolytica. This article presents a literature review on the properties of citric acid, the microorganisms and substrates used, different fermentation techniques, its industrial utilization, and the global citric acid market. This review emphasizes that there is still much to explore, both in terms of production process techniques and emerging new applications of citric acid.

Effect of soy protein hydrolysates incorporation on dough rheology, protein characteristic, noodle quality, and their correlations

Soy protein hydrolysates (SPHs) have bioactive and nutritional functions that can be used as fortifier of noodles. The objective of this study is to explore the effect of SPHs on dough rheology and noodle quality. Two kinds of SPHs, with a hydrolysis degree of 4.43% (SPH4) and 7.47% (SPH7), were added to wheat flour at a ratio of 5:95 to make dough and noodles. The addition of SPHs decreased the gluten yield, gluten index, peak viscosity, final viscosity, and setback of flour paste. Dough stability decreased, but the extensibility increased because of the addition of SPHs. SPHs decreased the high molecular weight glutenin subunits and SDS-unextractable polymeric protein proportion, and the results of scanning electron microscopy and atomic force microscopy also showed that the gluten network in SPH7 dough was more discontinuous than that in SPH4, suggesting a stronger negative effect of SPH7 on the formation of the gluten network compared to that of SPH4. The incorporation of SPHs decreased the hardness and springiness of cooked noodles but increased their cooking loss, protein loss, and water absorption. The correlation analysis showed that high molecular weight subunits and SDS-unextractable polymeric protein in SPH-fortified dough were positively correlated with the hardness, adhesiveness, springiness, cohesiveness, chewiness, resilience, force, and distance at break of noodles, and these texture properties of noodles were positively correlated with pasting, gluten, and farinographical properties of SPH-fortified flour. These results suggested that SPHs could improve some qualities of noodles, such as smoothness and cooking yield, and resist pasted starch aging. PRACTICAL APPLICATION: Soy protein hydrolysates have many bioactive functions. This study demonstrated the feasibility of incorporating soy protein hydrolysates into wheat flour to prepare noodles. The addition of soy protein hydrolysates gives noodles smoother mouthfeel and increases the cooking yield. The addition of soy protein hydrolysates decreases the setback value of flour paste, suggesting that soy protein hydrolysates may help to resist starch aging, which is favorable for starch-containing foods such as precooked noodles. Thus, soy protein hydrolysates possess potential applications in noodle products.

Co-precipitates proteins prepared by soy and wheat: Structural characterisation and functional properties

Co-precipitation was a novel method for improving the functional properties of pure proteins. To investigate the mechanism of this effect, different protein proportions of soy-wheat co-precipitated protein were extracted by isoelectric point co-precipitation. Soy protein isolate (SPI) was mainly linked to wheat protein (WP) through non-covalent forces and disulfide bonds as determined by circular dichroism spectroscopy, disulfide bond, protein fraction extraction, interaction, and molecular modeling. Amino acid analysis indicated that co-precipitation could increase wheat lysine content. Furthermore, co-precipitation improved multiple functional properties of pure protein, and the emulsifying and foaming properties of the composite system with a mass ratio of 7:3 outperformed those of other systems. At the same time, correlation analysis revealed that protein structure and intermolecular forces significantly affected its functional properties. This study provided some useful and interesting information for the development and application of protein-protein systems with diverse functional properties.

Protein deamidation to produce processable ingredients and engineered colloids for emerging food applications

With the ever-increasing demands for functional and sustainable foods from the general public, there is currently a paradigm shift in the food industry toward the production of novel protein-based diet. Food scientists are therefore motivated to search for natural protein sources and innovative technologies to modify their chemical structure for desirable functionality and thus utilization. Deamidation is a viable, efficient, and attractive approach for modifying proteins owing to its ease of operating, specificity, and cost-effective processes. Over the past three decades, the knowledge of protein deamidation for food applications has evolved drastically, including the development of novel approaches for deamidation, such as protein-glutaminase and ion exchange resin, and their practices in new protein substrate. Thanks to deamidation, enhanced functionalities of food proteins from cereals, legumes, milk, oil seeds and others, and thereby their processabilities as food ingredients have been achieved. Moreover, deamidated proteins have been used to fabricate engineered food colloids, including self-assembled protein particles, protein-metallic complexes, and protein-carbohydrate complexes, which have demonstrated tailored physicochemical properties to modulate oral perception, improve gastrointestinal digestion and bioavailability, and protect and/or deliver bioactive nutrients. Novel bioactivity, altered digestibility, and varied allergenicity of deamidated proteins are increasingly recognized. Therefore, deamidated proteins with novel techno-functional and biological properties hold both promise and challenges for future food applications, and a comprehensive review on this area is critically needed to update our knowledge and provide a better understanding on the protein deamidation and its emerging applications.

Highly Efficient Deamidation of Wheat Gluten by Glucose-Citric Acid-Based Natural Deep Eutectic Solvent: A Potential Effective Reaction Media

An efficient technique using citric acid and glucose based natural deep eutectic solvent (G-C-NADES) was developed to obtain ultrahigh deamidated wheat gluten (UDWG) (deamidation degree (DD) > 90%). FTIR and ¹H NMR indicated intensive hydrogen bonds (HBs) in G-C-NADES supermolecules. Quantum chemical calculations and molecular dynamic simulations demonstrated that 10 wt % diluted G-C-NADES still had a myriad of HBs. Physicochemical results showed UDWG had DD up to 92.45% after G-C-NADES deamidation, that is, 22% higher than citric-acid-DWG with a weak degree of hydrolysis (1.75%). Conformational characterization demonstrated the obvious conversion from α-helix to β-sheet via FTIR, the least amount of disulfide bonds by Raman spectra, and more exposure of tryptophan residues by fluorescence measurement for UDWG. It is proven that enhanced accessible conformation of WG reached with HBs of G-C-NADESs could contribute to the improvement on nucleophilic attack of deamidation, declaring that G-C-NADES might be a potential solvent for obtaining an ultrahigh deamidation for WG to successfully guarantee the safety of wheat gluten based cereal food regarding to lowering its allergy.

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.

Chemical modifications and their effects on gluten protein: An extensive review

Gluten protein as one of the plant resources is susceptible to genetic, physical, chemical, enzymatic and engineering modifications. Chemical modifications have myriad advantages over other treatments, including short reaction times, low cost, no requirement for specialized equipment, and highly clear modification effects. Therefore, chemical modification of gluten can be mainly conducted via acylation, glycosylation, phosphorylation, and deamidation. The present review investigated the impact of different chemical compounds on conformations of gluten and its subunits. Moreover, their effects on the physico-chemical, morphological, and rheological properties of gluten and their subunits were studied. This allows for the use of gluten for a variety of purposes in the food and non-food industry.

An erosion-type hydrolysis behavior of insoluble protein fraction from Chlorella protothecoides

BACKGROUND

Acid-induced hydrolysis of proteins has been used to improve the solubility and functional properties of various proteins, and could be a promising tool to facilitate the use of currently underutilized insoluble microalgae protein-rich fractions in food applications. However, the results of a prior study showed an unusual resistance of an insoluble microalgae protein-rich fraction to acid hydrolysis at room temperature.

RESULTS

In the present study, the insoluble protein-rich fraction extracted from microalgae Chlorella prothothecoides was treated with 0.5 mol L^-1 hydrochloric acid at 25, 45, 65 or 85 °C for 0-4 h. The results showed that hydrolysis of the fraction at 85 °C for 4 h led to decreases in the amount of insoluble protein-rich aggregates and the formation of fragments with a lower molecular weight, as well as an increase in protein solubility by approximately 40%. Nevertheless, some aggregated insoluble protein-rich particles remained, even after hydrolysis at 85 °C for 4 h.

CONCLUSION

The higher temperature improved the efficiency of the acid hydrolysis of the insoluble protein fraction from microalgae Chlorella prothothecoides, which is highly acid-resistant. Overall, an erosion-based mechanism was suggested for the acid hydrolysis of insoluble microalgae protein fraction. © 2019 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Interactions between soy protein hydrolyzates and wheat proteins in noodle making dough

Soy protein hydrolyzate has been used as supplements in wheat flour to enhance the nutritional value of its products, but it may negatively affect the gluten properties simultaneously. In order to explore the mechanism of this effect, protein characteristics including disulfide bond, protein composition, intermolecular force of dough proteins, and atomic force microscope images of gluten were obtained. Results showed that disulfide bonds in dough increased when soy protein hydrolyzate was added, but glutenin macropolymer decreased. Atomic force microscope images showed that gluten were weakened by soy protein hydrolyzate. Based on these results, a model was developed to describe the interaction between soy protein hydrolyzates and wheat proteins: soy protein hydrolyzates linked with wheat proteins through disulfide bond, disrupted the glutenins polymerization, thus hindered gluten networks formation. The interaction between wheat proteins and soy protein hydrolyzates in noodle making dough could be described with this model reasonably.

Enzymatic susceptibility of wheat gluten after subcritical water treatment

Subcritical water (SCW) hydrolysis is an alternative to traditional methods of protein hydrolysis that uses water as a reaction medium. In this study, the effect of SCW treatment on heat-induced conformational changes in wheat gluten and its relation to enzymatic susceptibility were investigated. The degree of deamidation increased rapidly from 12.5 to 47.4% with increase in the temperature range of 160-220 °C. Protein solubility increased in a similar pattern with degree of deamidation and almost all protein was solubilized after treatment with SCW at 200 °C. SCW treatment in a particular time-temperature combination results in a significant decrease in enzymatic susceptibility. After SCW treatment at 220 °C for 20 min, enzymatic susceptibility of gluten protein was exceedingly decreased to nearly complete loss. Because of excess degradation and deamidation and small molecular size (less than 6500 Da) many hydrolysis sites disappear and are difficult to access by protease.

Effect of the structural features of hydrochloric acid-deamidated wheat gluten on its susceptibility to enzymatic hydrolysis

The effect of the structural features of hydrochloric acid-deamidated wheat gluten with different degrees of deamidation (DDs) on the susceptibility to enzymatic hydrolysis by pancreatin was investigated. The wheat gluten deamidated by hydrochloric acid with a DD of 55% revealed the highest susceptibility to enzymatic hydrolysis as evaluated by the hydrolysis degree and nitrogen solubility index of the hydrolysates. An increase of peptides with MW below 3000 Da was observed as the DD increased. Raman spectra in the 1740-1800 cm⁻¹ and 521-530 cm⁻¹ range suggested that wheat gluten had taken off the deamidation with different DDs and that the disulfide bond had disrupted the sulfhydryl groups with different intensities, respectively. Results from the deconvolution of the amide I region of FTIR spectra in the 1600-1700 cm⁻¹ range showed that the content of the α-helix decreased and that the content of the β-turn and β-sheet increased with increasing DDs, which improved the molecular structure and flexibility of wheat gluten. A scanning electron microscope (SEM) revealed that the image of HDG-55% presented the smoothest surface and the least uniform pore, enabling the sample to be more susceptible to enzymatic hydrolysis. The above information will enable us to better understand the effect of structure on the susceptibility of deamidated wheat gluten.