Influence of wheat starch on rheological,structural and physico-chemical properties gluten–starch dough during mixing

This study mainly explored that the influence of wheat starch source on the rheology behaviours and structural properties of gluten–starch dough, and then the model doughs were prepared by the AK58 wheat gluten and three types of starches from strong (ZM366S), medium (AK58S) and weak gluten wheat (ZM103S) during mixing were studied. The damaged starch content of wheat starch was positively correlated with the wheat gluten strength, while the granule size was negatively. The G', G" and the extension resistance of ZM366S dough were higher than those of other doughs, which implied the source of starch also had a significant influence on the rheological properties. CLSM also observed that ZM366S was more closely bound to the gluten protein network. The glutenin macropolymer (GMP) content of ZM366S model dough was the highest, while the SH content was the lowest. Decreases in elasticity, extension and GMP, and small increase in SH content were displayed during dough mixing. Molecular forces were varied with different wheat starch and mixing time. The covalent bond was the main force between ZM103S and gluten, whereas the hydrogen and covalent bonds were the main force between ZM366S or AK58S and gluten. The interactions between ZM366 starch and gluten were stronger than others starch.     

酶制剂对全麦馒头面团水相溶液理化性质的影响

从单一戊聚糖酶(Pn)、葡萄糖氧化酶(Gox)以及双酶复合引起的面团水相理化特性变化层面揭示酶制剂对馒头品质的改良机制。结果表明:Pn和Gox均促进了面团水相溶液得率的提高,水相溶液中的蛋白和戊聚糖含量发生了显著的变化,气泡粒径大小和稳定性得到了显著的改善,界面蛋白吸附膜质地更为致密。Pn或Gox引起的面团水相溶液理化性质的变化,尤其是泡沫稳定性的改善,是全麦馒头比容增大、硬度减小、形成更加均匀和细腻的内部结构的重要原因之一。     

Relationship of polymeric proteins and empirical dough rheology with dynamic rheology of dough and gluten from different wheat varieties

Dynamic rheological properties of dough and gluten were studied and related to the empirical rheology (Farinograph) and the protein fractions of different wheat varieties. The relationship between high molecular weight-glutenin subunits (HMW-GS) and dough strength was evaluated. Dynamic rheology of under-, optimum- and over-mixed dough was also related to the farinograph characteristics and the protein fractions. The moduli (G′ and G″) of over- and optimally-mixed dough were significantly correlated with Farinograph characteristics and SDS-unextractable polymeric protein (UPP) content. The temperature-induced rheology of glutens revealed that the differences in G′ and G″ during heating as well as cooling were related to the UPP content. Principal component analysis revealed wide range of differences in the dynamic rheology among the wheat varieties mainly attributed to UPP.     

Impact of mixing time and sodium stearoyl lactylate on gluten polymerization during baking of wheat flour dough

The impact of differences in dough transient gluten network on gluten cross-linking during baking is insufficiently understood. We varied dough mixing times and/or added sodium stearoyl lactylate (SSL; 1.0% on flour dry matter basis) to the recipe and studied the effect on subsequent gluten polymerization during heating. The level of proteins extractable in sodium dodecyl sulfate containing media was fitted using first order kinetics. The extent and rate of gluten polymerization were lower when mixing for 8 min than when mixing for 2 min. This effect was even more outspoken in the presence of SSL. The present observations were explained as resulting from less gliadin incorporation in the polymer gluten network and from interaction of SSL with the gluten proteins. Finally, a higher degree of gluten polymerization during baking increased the firmness of the baked products.     

Aggregative and structural properties of wheat gluten during post-harvest maturation

Wheat post-harvest maturation induced baking and technological quality improvement through a series of biochemical and colloidal changes. Weak-, middle-, and strong-gluten wheat displayed varying gluten network structures that determined the flour ingredient formulations and processing conditions. However, the aggregation and structural properties of wheat with different gluten strengths post-harvest remain largely unexplored. In this study, we investigated changes in the aggregative properties of gluten protein, gluten composition, S–S content, network structure, and secondary structures of weak-, middle-, and strong-gluten wheat during post-harvest maturation. The results indicated that the macromolecular aggregation of gluten proteins was impaired in weak-gluten wheat, while it was enhanced for middle- and strong-gluten wheat during storage. Post-harvest maturation resulted in an increase in glutenin content and a decline in the gliadin and gliadin/glutenin ratio in middle- and strong-gluten wheat as well as a decreased glutenin content in weak-gluten wheat. Moreover, additional gluten subunits were observed in middle- and strong-gluten wheat, but no substantial change was observed in weak-gluten wheat with long storage times. The disulfide bond content of gluten protein for middle-gluten and strong-gluten gradually increased but declined for weak-gluten wheat. Secondary structure analysis of gluten indicated that post-harvest maturation caused the conversion of α-helix to random coil for weak-gluten wheat, β-turn and random coil to α-helix for middle-gluten wheat, and β-turns to α-helix for strong-gluten wheat, which led to a disordered structure for weak gluten and an ordered stable gluten network for middle- and strong-gluten. Thus, the increased S–S and α-helix content induced by post-harvest maturation enhanced the aggregation of gluten proteins for middle- and strong-gluten wheat, resulting in a denser network structure. Conversely, the decrease in the content of α-helix resulted in the existence of a looser gluten network structure for weak-gluten wheat during post-harvest maturation.     

谷朊粉在面团中作用机理的研究

通过Ellman’s试剂比色法测定添加谷朊粉的面粉蛋白质中的巯基和二硫键,同时研究了其在面团中的化学作用力,利用傅立叶变换红外光谱(FTIR)深入了解加入谷朊粉后面团的蛋白质和化学键的变化,同时讨论谷朊粉对面团吸水率、质构性质的影响。      

Role of gluten and its components in influencing durum wheat dough properties and spaghetti cooking quality

Protein is an important component of grain which affects the technological properties of durum wheat. It is known that the amount and composition of protein can influence dough rheology and pasta quality but the influence of the major classes of protein is not well documented. The influence of the various gluten components on dough and pasta properties was investigated. The protein composition of durum semolina was altered by either adding gluten fractions to a base semolina or preparing reconstituted flours with varying protein composition. The effects on semolina dough rheology and spaghetti texture were measured. Published methods to isolate relatively pure quantities (gram amounts) of glutenin, gliadin, high molecular and low molecular weight glutenin subunits were evaluated and modified procedures were adopted. Reconstituted flours with additional glutenin increased dough strength while additional gliadin and LMW‐GS decreased strength. These changes did not impact on spaghetti texture. Results from using the addition of protein fractions to a base semolina showed that gluten and glutenin addition increased the dough strength of a weak base semolina while gliadin addition weakened the base dough further. Addition of HMW‐GS greatly increased dough strength of the base while addition of LMW‐GS greatly reduced dough strength. Again, these affects were not translated into firmer pasta. Copyright © 2007 Society of Chemical Industry     

Prediction of the rheological properties of wheat dough by starch-gluten model dough systems: effect of gluten fraction and starch variety

The present study sought to investigate the rheological properties of wheat starch-gluten (WS-G) and potato starch-gluten (PS-G) model doughs with different gluten fractions to elucidate the effectiveness of using model dough to predict wheat dough properties. The highest linear viscoelastic region, frequency dependence, maximum creep compliance and the lowest viscoelastic modulus and zero shear viscosity were observed in the wheat dough, followed by WS-G and PS-G model doughs. PS exerted a more significant damage effect on the gluten network while WS shared a tight integration with gluten protein, forming a more stable dough structure. The viscoelasticity of the model doughs shared a close association with the wheat dough under increased gluten fraction, while the frequency dependence of the model doughs showed no trend towards wheat dough. Therefore, starch-gluten model dough could not fully stimulate the functionality of wheat dough irrespective of its gluten fraction.     

The polypeptide composition,structural properties and antioxidant capacity of gluten proteins of diverse bread and durum wheat varieties,and their relationship to the rheological performance of dough

The aim of this study was to compare five bread and five durum wheat genotypes for gliadins and glutenins profiles, the concentration of free sulphhydryl groups and disulphide bonds, antioxidant capacity of gluten proteins and their bread‐making performance. On average, bread wheat had significantly higher concentration of total sulphur‐rich (S‐rich) and sulphur‐poor (S‐poor) subunits of gliadins, as well as total low molecular weight (LMW) and high molecular weight (HMW) subunits of glutenins than durum wheat. However, durum wheat had higher concentration of S‐rich γ‐gliadins and S‐poor D‐LMW‐glutenins, but did not possess S‐poor ω‐gliadins. The concentration of disulphide bonds and total cysteine was higher in the durum gluten than that in the bread gluten, as well as antioxidant capacity (on average 90.6 vs. 85.9 mmol Trolox Eq kg^?1, respectively). In contrast to the bread wheat, the concentration of HMW‐glutenins was negatively associated with extensibility, as well as resistance to extension in durum wheat flour dough.     

A study on relationships between durum wheat semolina properties,technological mixing parameters and the properties of dough after mixing

Partial least square regression analysis was used to study the correlation between X variables (semolina quality, hydration level and mixing time) and Y variables, which were, in a first model, dough consistency during mixing, and, in a second model, dough properties after mixing (strength, elasticity, density) and leavening (maximum volume). The first model showed a predictive residual sum of squares (PRESS) of 2.98 and a predictive R² (Q²) of 0.92, and highlighted the key role of hydration and mixing time on dough consistency. The second model had the best PRESS (8.25) and Q² (0.94) values for dough volume and indicated that the volume increased with increasing mixing time until the dough consistency decreased of 20–30%. Dough volume was primarily affected by hydration. The model indicated that maximum volume after leavening, corresponding to optimum mixing time, was obtained with a soft and elastic dough, with a low‐density value.     

小麦面筋蛋白的性质和转谷氨酰胺酶对其成膜性能的影响

以小麦面筋蛋白为研究对象,探讨小麦面筋蛋白的性质,转谷氨酰胺酶的作用和制备条件对膜性能的影响。结果表明,酶用量为20U/g,反应时间为120min,pH为11,甘油/谷朊粉1:2.5,塑料平板作为成膜介质和乙醇体积分数均为40%～50%时,膜的抗拉强度增加51%,阻水性提高23%,透光率提高了5.48倍。扫描电镜显示膜的超微结构更加细致光滑。说明蛋白质的性质对其成膜性能的影响至关重要,酶处理有助于改善膜的机械性能和透光性,选择合理的制备条件,可得到性能优良的小麦面筋蛋白膜。     

Effects of processing on biochemical and rheological properties of wheat gluten proteins

Protein solubility increases during mixing at water absorption suitable for bread doughs. The changes that result from heat treatment may be much greater than the differences normally found among wheat varieties. Sheeting brings about a reduction in the gluten content and increase in gel protein content of doughs. This may be due to increase in temperature during sheeting as a result of work input to the dough resulting in protein denaturation. Drying at higher temperatures causes denaturation of pasta dough protein. In addition, it has been shown that high temperatures contribute to the formation of the protein network. During extrusion processing proteins are denatured and chemical bonds are weakened as result of heat and shear through the extruder.     

Effects of trypsin‐hydrolyzed wheat gluten peptide on wheat flour dough

BACKGROUND: Gluten peptide was prepared by trypsin hydrolysis and characterized by high‐performance liquid chromatographic analysis. The effects on non‐frozen and frozen doughs of trypsin‐hydrolyzed gluten peptide (THGP) and its combination with ascorbic acid or KBrO₃ were investigated. RESULTS: Molecular analysis of THGP showed a decrease in the high‐molecular‐weight and an increase in the low‐molecular‐weight sodium dodecyl sulfate‐soluble fractions, compared with those of control wheat gluten. The addition of 8% THGP decreased the mixing time and tolerance of the dough, both with and without ascorbic acid or KBrO₃. However, the maximum resistance and extensibility of the rested dough containing 8% THGP, with and without ascorbic acid or KBrO₃, were not significantly different from those of the control dough. The addition of 8% THGP significantly increased the loaf volume of bread baked from non‐frozen dough when combined with 60 ppm ascorbic acid or 30 ppm KBrO₃, but it had a significant effect both with and without ascorbic acid or KBrO₃ on frozen‐dough bread. A large difference in volume was observed between breads made with and without THGP at the oven‐spring, rather than at proofing. CONCLUSION: The addition of 8% THGP increased the loaf volume of bread made from freeze‐damaged dough and this effect increased when THGP was combined with 60 ppm ascorbic acid. Copyright © 2008 Society of Chemical Industry     

Effects of tannic acid on gluten protein structure,dough properties and bread quality of Chinese wheat

BACKGROUND: The effects of tannic acid, which is present in many plants, on the structure of gluten proteins and the properties of dough and bread were studied. Tannic acid was added at levels of 0.01, 0.02 and 0.03 g kg^?1 during the dough‐making process. RESULTS: The added tannic acid acted negatively on disulfide bond formation but interacted with gluten proteins via other covalent bonds, as detected by UV spectroscopy and dynamic rheometry. Rheological properties and texture of the bread were measured by farinograph, extensograph and texture profile analyser. Texture analysis indicated little change in adhesiveness and resilience of the bread at all three levels of tannic acid compared with the control, but changes in hardness and chewiness of the bread made with added tannic acid indicated that tannic acid could delay bread staling. CONCLUSION: The effect of tannic acid on flour and dough is different from that of other flour redox agents. It breaks down disulfide bonds but also has positive effects on dough properties and bread quality. Disulfide bonds are commonly considered to be the most important factor affecting changes in the quality of bread. However, this study presents the new concept that other covalent bonds can also improve the quality of flour and bread and uses this property to investigate new, safe and efficient flour additives. Copyright © 2010 Society of Chemical Industry     

Effects of isomalt on the quality of wheat flour dough and spicy wheat gluten sticks

The effects of different isomalt concentrations on the quality of wheat flour dough and spicy wheat gluten sticks (SWGS) were evaluated at the physical, structural and molecular levels. The results showed that the radial expansion rate (RER) and oil absorption rate (OAR) of SWGS increased first and then decreased with increased isomalt supplementation, which reached the maximum at 3 wt%. The pasting properties of wheat starch also changed, and the peak viscosity, breakdown and setback were decreased with the addition of isomalt. Dynamic rheological properties results showed that the storage modulus (G') and loss modulus (G'') increased with the addition of isomalt, which may be attributed to the reinforcement of gluten network structure by hydrogen bonding of isomalt. Scanning electron microscopy (SEM) images illustrated that the SWGS surface becomes smooth and the broken gluten structure was reduced after the addition of different isomalt levels compared with the control group. Overall, the wheat flour dough quality analysis showed that the addition of isomalt could generate a close binding with wheat starch and protein and further strengthen the internal structure of gluten through isomalt hydrogen bonds.     

Effects of processing on biochemical and rheological properties of wheat gluten proteins.

Protein solubility increases during mixing at water absorption suitable for bread doughs. The changes that result from heat treatment may be much greater than the differences normally found among wheat varieties. Sheeting brings about a reduction in the gluten content and increase in gel protein content of doughs. This may be due to increase in temperature during sheeting as a result of work input to the dough resulting in protein denaturation. Drying at higher temperatures causes denaturation of pasta dough protein. In addition, it has been shown that high temperatures contribute to the formation of the protein network. During extrusion processing proteins are denatured and chemical bonds are weakened as result of heat and shear through the extruder.     

Incorporation of gluten and hydrolysed gluten proteins has different effects on dough rheology and cookie characteristics

This study aims to establish how the substitution of wheat flour by high levels (15%, 30% and 45%) of gluten or hydrolysed gluten proteins affects sugar‐snap cookies properties. An increase in water‐binding capacity was observed when proteins were present. An increase in the dough elastic modulus was observed for gluten protein, but it decreased when hydrolysed gluten protein was used. Regarding the physical characteristics of the cookies, for the same protein percentage, the presence of gluten protein decreased spread ratio and increased hardness, while hydrolysed gluten protein increased spread ratio and yielded darker cookies without modifying the hardness. As for sensory characteristics, taste was negatively influenced by hydrolysed protein and visual acceptability was enhanced when gluten protein was present. Overall acceptability was decreased for the highest levels of hydrolysed gluten protein. Nevertheless, the highest levels of gluten protein did not modify the acceptability.     

绿色小麦面团流变学品质特性研究

以彩色小麦新品种—绿色小麦为研究对象,对绿色小麦的化学组成进行分析,测得绿色小麦蛋白含量为17.96%,高于黑色小麦、红麦和白麦。湿面筋测定结果显示,绿色小麦中湿面筋含量为35.5%。采用粉质仪、面筋强度仪、拉伸仪和流变仪对绿色小麦面团的流变学特性进行分析。测定结果表明,绿色小麦的面团形成时间、稳定时间都比其他品种小麦的短,分别为3.3min和1.8min;绿色小麦面团的抗拉伸性较其他小麦品种小;流变测定结果表明,绿色小麦面团中黏性比例较大,弹性与其他小麦相当。综合考虑,认为绿色小麦更适合于制作饼干或蛋糕。