Effect of konjac glucomannan on aggregation patterns and structure of wheat gluten with different strengths.

Konjac glucomannan (KGM) can act as a food additive to improve the quality of dough. The effects of KGM on the aggregation patterns and structural properties of weak, middle, and strong gluten were studied. We found that with a higher proportion of KGM substitution (10%), the aggregation energy of middle and strong gluten became lower than the control samples, while exceeding the control for weak gluten. With 10% KGM, aggregation of glutenin macropolymer (GMP) was enhanced for weak gluten, but suppressed for middle and strong gluten. The α-helix transferred to β-sheet in weak, but caused more random-coil structures for middle and strong gluten induced by 10% KGM. With 10% KGM, the network for weak gluten became more continuous, but severely disrupted for middle and strong gluten. Thus, KGM has distinct effects on weak, middle, and strong gluten, which related to the alteration of gluten secondary structures and GMP aggregation pattern.

Zhang X ，Tian Y ，Xing J ，Wang Q ，Liang Y ，Wang J ... -  《-》

Konjac glucomannan-induced changes in thiol/disulphide exchange and gluten conformation upon dough mixing.

Effects of konjac glucomannan (KGM) on the changes in gluten upon dough mixing were investigated in this study. Wheat flour was blended with KGM and processed into dough. Farinographic analysis showed that KGM caused a significant increase in water absorption and dough development time to reach maximum consistency. Comparison of electrophoretic protein profile from control dough and KGM-dough revealed that protein fractions were similar in molecular size distribution, but the lability of glutenin aggregates slightly differed. Addition of KGM to gluten induced negative effects on exchange between sulfhydryl groups and disulphide bonds. Fourier transform-Raman spectroscopy indicated that secondary structure of gluten proteins was differentially modified related with water absorption of flours before dough formation. This study reveals that when KGM is added to the dough, conformational behaviours of gluten proteins are changed and the hydroxyl groups of KGM might be involved in the interaction by forming strong intermolecular hydrogen bonding system.

Zhou Y ，Zhao D ，Foster TJ ，Liu Y ，Wang Y ，Nirasawa S ，Tatsumi E ，Cheng Y ... -  《-》

Effects of konjac glucomannan on heat-induced changes of wheat gluten structure.

Effects of konjac glucomannan on the structure of wheat gluten were investigated at variable temperatures in this study. Dynamic oscillatory rheology study showed that konjac glucomannan conferred stiffness on gluten with a higher tan δ data at 25°C and 55°C, but this parameter was lower at 75°C and 95°C. Konjac glucomannan decreased the content of thiol equivalent groups and increased the α-helix/β-sheet content ratio, respectively. The thicker layer of gluten protein with 5% konjac glucomannan was observed by scanning electron microscopy. This study revealed that konjac glucomannan could alter the conformations of gluten proteins upon heating via non-covalent interactions and physical entanglements. It is likely that konjac glucomannan promotes protein aggregation by strengthening hydrophobic interaction at 25°C and 55°C, and alleviates heat-induced denaturation by decreasing the flexibility of polypeptide chain at higher 75°C and 95°C.

Wang Y ，Chen Y ，Zhou Y ，Nirasawa S ，Tatsumi E ，Li X ，Cheng Y ... -  《-》

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.

Zeng Z ，Guan X ，Qin X ，Chen Z ，Liu X ... -  《-》

Synergistic effects of oxidized konjac glucomannan on rheological, thermal and structural properties of gluten protein.

Oxidation is an effective way to prepare depolymerized konjac glucomannan (KGM). The oxidized KGM (OKGM) differed from native KGM in physicochemical properties due to different molecular structure. In this study, the effects of OKGM on the properties of gluten protein were investigated and compared with native KGM (NKGM) and enzymatic hydrolysis KGM (EKGM). Results showed that the OKGM with a low molecular weight and viscosity could improve rheological properties and enhance thermal stability. Compared to native gluten protein (NGP), OKGM stabilized the protein secondary structure by increasing the contents of β-sheet and α-helix, and improved the tertiary structure through increasing the disulfide bonds. The compact holes with shrunk pore size confirmed a stronger interaction between OKGM and gluten protein through scanning electron microscopy, forming a highly networked gluten structure. Furthermore, OKGM depolymerized by the moderate ozone-microwave treatment of 40 min had a higher effect on gluten proteins than that by the 100 min treatment, demonstrating that the excessive degradation of KGM weakened the interaction between the gluten protein and OKGM. These findings demonstrated that incorporating moderately oxidized KGM into gluten protein was an effective strategy to improve the properties of gluten protein.

Chen Z ，Li Y ，Wang H ，Tian H ，Feng X ，Tan L ，Liu X ... -  《-》