Effect of different treatment methods on protein aggregation characteristics in wheat flour maturation

Effects of thermal treatment and Glucono-δ-lactone on the quality of alkaline dough and steamed buns

In the present study, the effects of glucono-δ-lactone (GDL) as an acid reagent during thermal treatment on the quality of alkaline dough and steamed buns were examined. During the heating process, GDL improved the viscoelasticity and fluidity of the alkaline dough and enhanced intermolecular hydrogen bonding. The hardness of steamed buns was reduced by 61.04 %, whereas the specific volume was increased by 10.4 % with 0.8 g of GDL. The color and taste were also improved to a certain extent. Scanning electron microscopy revealed that excessive GDL caused the dissolution of the gluten network and reduced the formation of gluten protein aggregates. During the heating process, GDL is beneficial to the aggregation of the gluten network. During the process of heating from 25 °C to 60 °C, GDL reduced the -SH content and zeta potential in gluten proteins, enhanced thermal stability, and formed a more ordered gluten network. Excessive GDL reduces the pH of the system by approximately 50 %, causing gluten network dissolution and the reduced formation of gluten protein aggregates. When the temperature increased from 60 °C to 95 °C, a stable gluten network system was formed inside the alkaline dough, and GDL changed the pH of the dough by reacting with sodium bicarbonate, resulting in greater elasticity and lower hardness of the dough. These results provide a theoretical basis for using GDL as an acid reactant for chemical fermentation.

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.

Flour Treatments Affect Gluten Protein Extractability, Secondary Structure, and Antibody Reactivity

Commercial Brazilian wheat flour was subjected to extrusion, oven, and microwave treatments. The solubility, monomeric and polymeric proteins, and the glutenin and gliadin profiles of the gluten were analyzed. In addition, in vitro digestibility and response against potential celiac disease immune-stimulatory epitopes were investigated. All treatments resulted in low solubility of the polymeric and monomeric proteins. The amounts of insoluble proteins increased from 5.6% in control flour to approximately 10% for all (treatments), whereas soluble proteins decreased from 6.5% to less than 0.5% post treatment. In addition, the treatments affected glutenin and gliadin profiles. The amount of α/β-gliadin extracted decreased after all treatments, while that of γ-gliadin was unaffected. Finally, the potential celiac disease immune stimulatory epitopes decreased in oven and microwave treatment using the G12 ELISA, but no change was observed using the R5 antibody. However, the alteration of the gluten structure and complexity was not sufficient to render a product safe for consumption for individuals with celiac disease; the number of potential celiac disease immune-stimulatory epitopes remained high.

Change in volatile profiles of wheat flour during maturation

The volatile profiles of wheat flour during maturation were examined through headspace solid-phase micro-extraction gas chromatography-mass spectrometry (HS-SPME-GC/MS) combined with electronic nose (E-nose) and electronic tongue (E-tongue) analyses. The wheat flour underwent maturation under three distinct conditions for predetermined durations. While GC/MS coupled with E-tongue exhibited discernment capability among wheat flour samples subjected to varying maturation conditions, E-nose analysis solely relying on principal component analysis failed to achieve discrimination. 83 volatile compounds were identified in wheat flour, with the highest abundance observed in samples matured for 50 d at 25 °C. Notably, trans-2-Nonenal, decanal, and nonanal were the main contributors to the characteristic flavor profile of wheat flour. Integration of HS-SPME-GC/MS with E-tongue indicated superior flavor development and practical viability in wheat flour matured for 50 d at 25 °C. This study furnishes a theoretical groundwork for enhancing the flavor profiles of wheat flour and its derivative products.

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.

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

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