Effect of low-sodium salt on the physicochemical and rheological properties of wheat flour doughs and their respective gluten

Protein aggregation behavior and structural characteristics in a lipoxygenase-linoleic acid-wheat gluten model system

This study explores the synergistic effects of linoleic acid (LA) oxidation on the aggregation behavior and structural properties of wheat gluten (WG). Using lipoxygenase to induce LA oxidation, it was observed that this process significantly influenced WG's viscoelasticity and structural characteristics. Specifically, LA oxidation enhanced WG's viscoelastic properties while reducing its instantaneous elastic and recovery deformations. The optimal viscoelasticity occurred with 0.1 mL/g of LA and a reaction time of 60 min. From the perspective of aggregation behavior, increasing LA concentration reduced hydrophobic interactions while significantly boosting disulfide bond formation and stabilizing secondary structures such as α-helices and β-sheets. Complementary analyses using SE-HPLC and RP-HPLC confirmed that LA oxidation intensified the covalent aggregation of WG. Furthermore, confocal laser scanning microscopy revealed that LA oxidation resulted in a more homogeneous WG structure, characterized by smaller pore sizes and more branched gluten networks. In conclusion, the oxidation of LA effectively promotes covalent cross-linking in WG, leading to improved structural and functional properties. These findings provide valuable insights into the oxidation mechanisms of WG and potential strategies for modulating its properties in food applications.

Changes in rheological properties and structure of wheat gluten proteins induced by transglutaminase

To elucidate the effect of transglutaminase (TG) on the rheological properties of wheat gluten, this study investigates the underlying mechanisms by analyzing changes in gluten structure. The results demonstrated that the TG-treated gluten samples had higher storage modulus (G') and loss modulus (G″) compared to the control, conversely, creep and recovery strains followed an opposite trend. Notably, the most pronounced effects were observed with adding 2 U/g TG for 20-30 min. Size exclusion/reversed phase-high performance liquid chromatography profiles revealed that the treatment with TG elevated the levels of glutenin subunits, alongside reduced α- and γ-gliadins, promoting gluten aggregation. Moreover, the extractability of gluten gradually decreased due to TG-induced oxidation of sulfhydryl groups, which formed new disulfide bonds and cross-linked products. This structural modification reduced surface hydrophobic regions and promoted the aggregation of low molecular weight proteins into larger molecular weight aggregates. Microstructural analysis further confirmed that TG enhanced gluten network stability through covalent cross-linking. Overall, this study demonstrates that TG enhances the rheological characteristics of wheat gluten by facilitating the formation of a more robust network structure, driven by cross-linking reactions and disulfide bond formation.

Physicochemical and microstructural properties of frozen cooked noodles during frozen storage affected by enzymatically interesterified soybean oil-based plastic fat

The quality deterioration of frozen cooked noodles (FCNs) during frozen storage remains a challenging problem, primarily characterized by a decline in textural performance. The objective of this study was to investigate the underlying mechanism responsible for the improvement in FCNs quality by utilizing enzymatically interesterified soybean oil-based plastic fat (EIPF). During the 12-week frozen storage, an improvement in hardness, from 3421.44 g to 3981.91 g, and a decrease in adhesiveness, water absorption rate, and cooking loss, from 177.49 g.s to 153.54 g.s, 80.46 % to 70.43 %, and 2.86 % to 2.16 %, respectively, were observed after adding 1 % of EIPF. The results demonstrated that 1 % EIPF significantly (P < 0.05) mitigated the decline in the quality of FCNs. Additionally, EIPF effectively restrained the transformation and migration of water and resulted in decrease in SDS-soluble gluten content and SH/S-S ratio in FCNs during frozen storage. The addition of 1 % EIPF increased α-helixes and decreased random coils, indicating greater network stability. Microscopic observation further confirmed that the addition of EIPF promoted the formation of dense gluten network. The current study positions EIPF as a promising additive for enhancing the quality of FCNs, thereby promoting its application in food industry.

Insights into the enhancement mechanism of rheological properties of dough induced by wheat flour maturation: The view from gluten proteins aggregation

To elucidate the mechanisms underlying the changes in the rheological properties of dough made from wheat flour during maturation, the molecular structure of gluten before and after maturation was characterized. Wheat flour was matured under three distinct conditions for predetermined durations. The development time, stability, and maximum force of dough peaked at 7.10 min, 8.58 min, and 88.98 N, respectively, after 40 days of maturation at 25 °C and 40 °C. Compared to the control, the storage modulus of dough made from wheat flour matured at 40 °C increased, while creep compliance decreased, indicating improved deformation resistance and a closer resemblance to viscoelastic solid materials. SDS-PAGE and molecular weight distribution indicated that maturation induces the binding of gluten peaks, evoking small molecular weight proteins to form larger protein clusters through folding. Compared to the control, the content of disulfide bonds significantly (P < 0.05) increased, tightening the protein network, while fluorescence intensity decreased after 40-50 days. This is accompanied by a distinct cross-linkage structure, confirmed by AFM. Among the three maturation conditions, 40 °C had the most pronounced effect, followed by 25 °C. This study offers insights and a theoretical basis for adjusting maturation conditions to enhance wheat flour quality.

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

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

Effect of high-molecular-weight glutenin subunits silencing on dough aggregation characteristics

The qualities of wheat dough are influenced by the high-molecular-weight glutenin subunits (HMW-GS), a critical component of wheat gluten protein. However, it is still unknown how HMW-GS silencing affects the aggregation characteristics of dough. Two groups of near-isogenic wheat were used to study the effects of HMW-GS silencing on dough aggregation characteristics, dough texture characteristics, and dough microstructure. It was observed that the content of gliadin in LH-11 strain significantly increased compared to the wild-type (WT). Additionally, the amount of glutenin macropolymer and the glutenin/gliadin both decreased. The aggregation characteristics and rheological characteristics of the dough in LH-11 strain were significantly reduced, and the content of β-sheet in the dough was significantly reduced. The HMW-GS silencing resulted in a reduction in the aggregation of the gluten network in the dough, which related to the alteration of the secondary and microstructure of the gluten.

Effect of sanxan on the composition and structure properties of gluten in salt-free frozen-cooked noodles during freeze-thaw cycles

In this study, the mechanisms by which sanxan protected the quality of salt-free frozen-cooked noodles (SFFCNs) were investigated, with a focus on the composition and structural properties of gluten. The results showed that sanxan facilitated the formation of glutenin macropolymer and maintained the stabilization of glutenin subunits in freeze-thaw cycles (FTs). In terms of protein structure, sanxan weakened the disruption of secondary structure caused by FTs and increased the proportion of gauche-gauche-gauche (g-g-g) conformations in the disulfide (S-S) bonds bridge conformation. Simultaneously, sanxan reduced the exposure degree of tryptophan (Trp) and tyrosine (Tyr) residues on the protein surface. Moreover, the intermolecular interaction forces indicated that sanxan inhibited S-S bonds breakage and enhanced the intermolecular crosslinking of gluten through ion interactions, which was crucial for improving the stability of gluten. This study provides a more comprehensive theoretical basis for the role of sanxan in improving the quality of SFFCNs.

Psyllium Fibre Inclusion in Gluten-Free Buckwheat Dough Improves Dough Structure and Lowers Glycaemic Index of the Resulting Bread

The demand for gluten-free (GF) bread is steadily increasing. However, the production of GF bread with improved baking quality and enhanced nutritional properties remains a challenge. In this study, we investigated the effects of adding psyllium fibre (PSY) in varying proportions to buckwheat flour on the dough characteristics, bread quality, and starch digestion properties of GF bread. Our results demonstrate that incorporating PSY contributes to the formation of a gluten-like network structure in the dough, leading to an increase in the gas holding capacity from 83.67% to 98.50%. The addition of PSY significantly increased the specific volume of the bread from 1.17 mL/g to 3.16 mL/g. Bread containing PSY displayed superior textural characteristics and colour. Our study also revealed that the inclusion of PSY reduced the digestibility of starch in GF bread. These findings highlight the positive impact of incorporating PSY into GF bread, suggesting its potential in guiding the production of GF bread with a lower glycaemic index. This may be particularly beneficial for individuals seeking to regulate their blood sugar levels or adopt a low-glycaemic diet.

Correlation Analysis between Wheat Flour Solvent Retention Capacity and Gluten Aggregation Characteristics

Solvent retention capacity (SRC) is a test for the solvation of wheat flour. Its functional contribution was predicted according to the swelling behavior of different diagnostic solvents to different polymeric components of wheat. Ten commercial wheat flour varieties were used as raw materials in this study. The flour quality, gluten aggregation and solvent retention capacity, and their correlations were analyzed. The results showed that protein content, wet gluten content, dry gluten content and the swelling index of glutenin were positively correlated with torque maximum (BEM), torque 15 s before maximum torque (AM), torque 15 s after maximum torque (PM) and gluten aggregation energy (AGGEN). Moreover, they were significantly correlated with the solvent retention capacity. BEM, AM, PM and AGGEN were positively correlated with standard solvent water-SRC (WSRC) and lactic acid-SRC (LASRC). For supplemental solvents, ethanol-SRC (EthSRC) was positively correlated with AGGEN. Sodium dodecyl sulphate-SRC (SDSSRC) was highly correlated with peak maximum time (PMT). Metabisulfite-SRC (MBSSRC) and MBS + SDSSRC were also significantly correlated with BEM, AM, PM and AGGEN sodium metabisulfite. There were significant correlations between gluten aggregation characteristic, standard SRC solvent and supplemental solvent. This study provides a theoretical basis for the evaluation of wheat flour quality.

Effect of sanxan gel on the quality of salt-free noodles during cooking

The effect and mechanism of sanxan on the quality of salt-free noodles (SFNs) were investigated from different cooking stages (initial stage, 1 min; optimum cooking time, OCT; overcooked time, OT). The results showed significant changes in the cooking process with the addition of 1.2% sanxan. The OCT for noodles with 1.2% sanxan (experimental group, EG) was extended from 5 to 7 min compared to the non-added noodles (blank group, BG) and 1.5% salt-containing noodles (control group, CG). The hardness and adhesiveness of BG, EG, and CG all decreased significantly during cooking. In contrast, the springiness, maximum tensile strength, and tensile fracture distance trended first to increase and then to decrease. At OCT, EG had the highest hardness (3971.69 ± 94.49 g), adhesiveness (372.26 ± 33.56 g s), and maximum tensile strength (41.51 ± 2.76 g), which remained large even after overcooking. However, those in BG and CG showed a significant reduction (p < 0.05). The proportion of free water increased progressively as cooking progressed, with CG showing the largest increase, from 82.29% to 91.19%, whereas EG showed the smallest increase, from 78.34% to 86.02%. During the cooking process, the addition of sanxan delayed the water migration, whereas salt promoted it. Sensory evaluation showed that EG was smoother in appearance than BG and tasted malty with a slight stickiness. Moreover, EG had the smallest k₁ and C_∞ values. Thus, sanxan is an effective additive to enhance the quality of SFNs and can replace the role of salt in noodles in some properties, which is beneficial for the development of SFNs.

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.