Behavior of wheat flour dough at different pretreated temperatures through rheological characteristics and molecular interactions of proteins.

Rheological properties and chemical interactions of doughs prepared at different temperatures were evaluated. The results showed that the rigidity of pretreated doughs was enhanced, and the processing performance of doughs was weakened. Preheating resulted in the polymerization of gluten through the conversion of sulfhydryl groups to disulfide bonds. The noncovalent interaction of dough played a dominant role and further led to the production of glutenin macropolymers (55.77 mg/g). CLSM images verified that preheating promoted the formation of the coarse and scattered gluten network, while preheating at 80 °C led to a higher gluten area percentage (40.27 %) and lower lacunarity (6.74 × 10-2) structure. The migration of water promoted changes in hydrogen bond and hydrophobic interaction in doughs, which directly affect the processability of doughs. The study provides information for predicting the rheological behavior of dough in actual production and makes it possible to modify gluten by preheating treatment without complicating existing operations.

Mechanical action on the development of dough andits influence on rheological properties and protein network structure.

Four simple dough preparation methods were proposed to imitate the rheological behaviors of traditional hand-made doughs and the underlying mechanism was concomitantly elucidated. It indicated the hand-made doughs, including the conventional hand-made dough (CHD), bidirectional pressed dough (BPD), bidirectional rolled dough (BRD), unidirectional pressed dough (UPD), and unidirectional rolled dough (URD), showed weaker mechanical resistance than the mixer-made dough did. Compared with UPD and BRD, BPD and URD had better tensile resistance and deformation recovery. CLSM analysis showed that these two doughs also possessed smaller lacunarity (7.22-7.24 × 10-2) and larger branching rate (0.23 × 10-2), suggesting bidirectionally pressing and unidirectionally rolling could produce a dough with better gluten network connectivity. Analysis of gluten protein solubility showed that the stronger hydrogen bonds and hydrophobic interactions of gluten protein were derived in rolled doughs (URD and BRD), and the stronger slip caused by intermediate water in pressed doughs (UPD and BPD) may lead to the high gluten extractability. In addition, more disulfide bonds were formed in BPD (3.37 µmol/g) and URD (3.62 µmol/g), promoting the stronger mechanical resistance in BPD and URD. Nevertheless, pressing or rolling promoted no statistically significant increase in the content of glutenin macropolymers. Physical entanglement caused by the recombination of noncovalent interactions may be the main cause. In conclusion, theeffect ofmanual external forces ondough qualitywasverified theoretically, and gluten network analysis can quantitatively evaluate dough microstructural changes.

Interactions between wheat globulin and gluten under alkali or salt condition and its effects on noodle dough rheology and end quality.

The influences of wheat globulin on dough and noodle quality under alkali or salt conditionwere investigated, and the protein interactions were revealed. Results indicated that dough viscoelasticity, noodle hardness, springiness and extensibility of samples with globulin added were remarkably increased under alkali condition. However, the corresponding enhancement was less significant under salt condition. In dough system, added globulin decreased the protein surface hydrophobicity by 38.71%, implying the enhancement of hydrophobic interactions. Under salt and alkali conditions, added globulin further increased the ß-sheets structure by 1.68% and 3.17%, respectively, indicating the enhancement of hydrogen bonds interaction. In addition, disulfide bonds interactions between globulin and gluten have also been demonstrated induced by alkali. The results were accountable for protein network polymerization observed in micro-structures. This paper provides new insights into the structural properties of wheat globulin, and demonstrates the excellent potential to improve noodle processing quality under alkali condition significantly.

Impact of wheat globulin addition on dough rheological properties and quality of cooked noodles.

Impact of globulin addition on the functional and protein structural properties of dough and cooked noodles were investigated. The underlying mechanism was explored through analyzing the interaction between globulin and gluten by using SDS-PAGE, size exclusion chromatography, free sulfhydryl/disulfide bond analysis, laser scanning confocal microscopy and Fourier transform infrared spectroscopy. Results showed that the stiffness/hardness and maximum resistance of dough and cooked noodles were both increased when globulin addition was 1.5% or higher. Besides, extensibility of cooked noodles was also improved when the addition up to 3.0%. The addition of globulin facilitated weakening the S-S bonds in the gluten network and cross-linked with SDS-soluble gluten mainly through non-covalent interactions, especially hydrophobic interactions. Meanwhile, a more rigid protein network structure was observed. Additionally, following cooking, globulin addition accelerated the aggregation of protein molecules. When the addition reached 3%, the protein conformation was transformed from ß-sheets and random coils to ß-turns.

Effects of vacuum degree, mixing speed, and water amount on the moisture distribution and rheological properties of wheat flour dough.

Effects of vacuum degrees (0.00, 0.02, 0.04, 0.06, 0.08 MPa) on water distribution state, tensile properties, stress relaxation properties, and viscoelasticity of dough, as well as the effects of mixing speed (50, 70, 90 rpm/min) and water content (40%, 45%, 50%) under optimum vacuum degree were studied. The results showed that the proper vacuum degree (0.06 MPa) could promote the full contact between flour and water and improved the water-holding capacity of the dough. Meanwhile, the dough had stronger tensile strength, the best viscoelasticity and the ability to recover from external deformation more quickly. Under the vacuum of 0.06 MPa, with the increasing of mixing speed, the response to the external force of dough increased first and then decreased. Adding more water reduced the strength of dough, weakened the response to external forces, and led to a significant decrease in tensile resistance and tensile area of the dough, as well as a decrease in viscoelasticity (p < 0.05). The proper vacuum mixing allowed the preparation of dough to require more water and less energy. PRACTICAL APPLICATION: In the processing of wheat flour products, vacuum mixing is considered to be beneficial to the quality of noodles and breads. As the intermediate of these products, the dough is of great significance for the monitoring of its rheological characteristics. In this study, a moderate vacuum degree led to a significant improvement in the rheological properties of the dough, and the processing performance was the best. Under the optimal vacuum degree, the influence of mixing speed and water amount cannot be ignored. Vacuum mixing is an efficient dough preparation method, which can produce certain economic benefits.