Rheological and microstructural characterization of wheat dough formulated with konjac glucomannan.

This work aimed to investigate the effects of different levels of konjac glucomannan (KGM) on the thermomechanical and pasting properties, water distribution, gelatinization, texture, and microstructural characteristics of wheat flour and dough. The thermomechanical properties assessed with a Mixolab showed that KGM could increase the water absorption and degree of softening and decrease the stability time of wheat dough. In addition, wheat flour starch with KGM underwent significant (P < 0.05) gelatinization changes according to the rapid viscosity analyzer and differential scanning calorimetry results. These results demonstrated that KGM enhanced the thermal stability and anti-aging capacity of wheat flour. All doughs with KGM exhibited viscoelastic behavior but lower hardness and gumminess. Low-field nuclear magnetic resonance showed that water, with a tight binding force, migrated to the weaker binding forces in the dough. A noticeable disruption of the gluten network was observed at the highest level of KGM. However, an intermediate level of KGM addition (10 or 15 g kg-1 flour) still rendered dough with satisfactory properties. A certain amount of KGM could enhance the thermal stability and anti-aging ability of wheat flour, improve the viscoelastic behavior, and decrease the hardness and gumminess of dough. In general, the mixing of flour and dough with KGM addition of 10 or 15 g kg-1 flour was of good quality. © 2021 Society of Chemical Industry.

Meng K ，Gao H ，Zeng J ，Zhao J ，Qin Y ，Li G ，Su T ... -  《-》

Effect of konjac glucomannan with different viscosities on the quality of surimi-wheat dough and noodles.

It was investigated that the rheology, starch-gluten-surimi network, thermal properties, and water distribution of surimi-wheat dough, and texture characteristics, cooking properties, and microscopic characteristics of the surimi-wheat noodles with konjac glucomannan (KGM) of different viscosities in different concentrations. The results showed that the storage (G'), loss (G″), and complex (G⁎) moduli of dough increased with adding KGM. With the increase of KGM viscosity, the reduction in the free sulfhydryl (SH) content to 0.84 μmol/g and the increase in the free water content to 8.25 % led to significantly improved enthalpy and the microstructure density. The hardness and tensile length of noodles were substantially increased by adding 3 % KGM. In addition, the KGM enhanced the starch-gluten-surimi network and improved the cooking qualities and textural properties of noodles. More importantly, the application of KGM in the wheat flour composite system also showed better performance. Thus, the introduction of KGM into the surimi-wheat dough had a significant effect on the optimization of the macro- and micro-characteristics of dough and noodles.

Cao G ，Chen X ，Wang N ，Tian J ，Song S ，Wu X ，Wang L ，Wen C ... -  《-》

Effects of Konjac glucomannan with different viscosities on the rheological and microstructural properties of dough and the performance of steamed bread.

Konjac glucomannan (KGM) is used as an additive to improve the properties of wheat products. The effects of three types of KGM on the rheological properties and microstructure of dough, as well as the performance of steamed bread were investigated in this study. Particularly, dough with KGM displayed new features such as reduced peak viscosity, breakdown and setback. As the viscosity of KGM increased, the stability of the dough structure increased, while the viscosity and fluidity of the dough decreased. More interestingly, the gluten film of dough also increased with increasing substitution level and viscosity of KGM. Consistently, KGM with higher viscosity improved the quality of steamed bread. Generally, three types of KGM have different effects on the rheological characteristics and microstructure of dough, as well as the performance of steamed bread, which provide useful information for the proper application of KGM in wheat-based foods.

Guo J ，Liu F ，Gan C ，Wang Y ，Wang P ，Li X ，Hao 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 whey and soy protein addition on bread rheological property of wheat flour.

The development of wheat-based foods that are enriched with proteins is increasingly popular due to consumer demand regarding food nutritional content and quality. This study was performed to compare the effect of whey and soy protein on the rheological properties of wheat dough and bread-making quality in a relatively wide range of protein addition (0-30%). We found that the incorporation of whey protein (WP) decreased dough stability time (MST), minimum torque (MMT), G' and G″, but increased dough peak torque (MPT), stickiness, G' and G″ in temperature sweep. With the increasing level of WP from 0 to 30%, the specific volume of bread initially decreased from 2.61 to 2.22 cm3 /g, then increased to 3.08 cm3 /g when WP was at higher concentration than gluten. However, the crumb hardness increased from 173 to 1291 g at the same time. As a contrast, the addition of soy protein (SP) increased dough MST, MMT, G' and G″, but decreased MPT, stickiness, G' and G″ in temperature sweep. With the increasing level of SP from 0 to 30%, the specific volume of bread decreased from 2.61 to 1.31 cm3 /g and the hardness first decreased from 173 to 152 g, then increased to 696 g. The results suggested that selection of the protein source and amount with appropriate functionalities played an important role in certain applications for protein fortified bakery products. Since it is known that the gluten network is responsible for viscoelastic properties in wheat dough and for dough structure strength and gas retention, most studies reported that enrichment of foreign proteins interfered with gluten development and therefore, had negative effects on bread quality. This study compared the effects of whey and soy proteins on the thermomechanical, dynamic rheological and microstructural properties of wheat dough and bread-making quality in a relatively wide range of protein addition (0-30%). The results suggested that selection of the protein source and amount with appropriate functionalities significantly affected the structure of the dough and quality of the bread. Our study is essential for product development and process control when considering the popularity of protein fortified bakery products.

Zhou J ，Liu J ，Tang X 《-》