Enhancing the Rheological Performance of Wheat Flour Dough with Glucose Oxidase,Transglutaminase or Supplementary Gluten

The enzymes glucose oxidase and transglutaminase are frequently used to improve the breadmaking performance of wheat flours, as they have the ability to considerably alter the viscoelastic nature of the gluten network. To evaluate a flour’s breadmaking performance, rheological tests offer an attractive framework. In this study, the rheological impact of adding glucose oxidase or transglutaminase to wheat flour dough is investigated by means of linear oscillatory shear tests, creep-recovery shear tests and startup extensional tests. The former tests reveal that the enzymes render the dough stiffer and enhance its elastic character, until saturation is reached. In the breadmaking process, the use of excessive amounts of enzyme is known to be counterproductive. The strain-hardening index clearly reveals this overcross-linking effect. Besides enzymes, the gluten network can also be reinforced by adding supplementary gluten, which was indeed found to enhance the extent of strain-hardening.     

Impact of oleuropein on rheology and breadmaking performance of wheat doughs,and functional features of bread

Oleuropein (OP) is a polyphenol present in drupes and leaves of olive tree with health benefits and, as antioxidant, potentiality to alter gluten functionality. Effects of OP inclusion to wheat flour (0.01% and 0.02% on flour weight basis) on dough rheology and breadmaking performance, and bread features were investigated. Farinograph, uniaxial extension and shear rheometry (oscillatory and creep-recovery) were applied. Doughs containing OP were stronger, more elastic, and less sticky indicating the ability of OP to act as flour improver. The strengthening effect of OP on gluten led to the increase in bread volume and softer crumb compared to control. A lower crumb density of bread with the addition of OP was related to a higher in vitro glycaemic response. An increase in the antioxidant capacity of bread made with the phenolic compound was also found.     

Dough microstructure: Novel analysis by quantification using confocal laser scanning microscopy

The effect and the correlation of water addition to flour on the microstructure and viscoelastic properties of wheat flour dough were investigated using confocal laser scanning microscopy and a spectrum of rheological methods. Dough with water addition in the range of 52.5-70.0 g water 100 g⁻¹ flour was investigated using a stickiness test, uniaxial elongation test, and fundamental rheology like small amplitude oscillatory shear measurement and a creep recovery test. A method for quantifying the microstructure of dough protein gained by CLSM was established with image processing and analysis. The complex shear modulus decreased rapidly with water addition due to the plasticization effect of water molecules and increased mobility in the continuous phases. Elastic behavior, determined as loss factor tan ?? and relative elastic part J_el decreased. Rheological tests showed high linear correlations with each other (r of |0.66|-|0.98|). Image analysis measurements (average size, area fraction, perimeter, circularity, and fractal dimension) showed high linear correlations (r of |0.66|-|0.85|) with water addition and rheological attributes like the complex shear modulus (r = 0.85) and J_el (r = 0.86). CLSM in combination with image processing and analyzing has proven to be an applicable and powerful tool for examining and quantifying dough protein microstructure. Hence, it was possible to prove the dependency of rheology on the microstructure of dough.     

Rheological properties of yeasted and nonyeasted wheat doughs developed under different mixing conditions

BACKGROUND: In order to explore the differences in rheological behaviour of full formula and flour/water doughs due to mixing, small‐amplitude oscillatory strain (SAOS) rheological measurements were made on fully developed nonyeasted and inactivated yeasted dough formulations mixed at various speeds using the Brabender Farinograph and the Bohlin ReoMixer. These results were compared with large‐strain empirical rheological results (including Kieffer rig uniaxial extension) as well as baking test results to determine differences due to mixer speed and/or flow distribution. RESULTS: The uniaxial extension and baking tests detected mixing speeds with incomplete dough development. Above those speeds, energy input to peak development was relatively constant in the Farinograph. Extensibility trends showed increases with speed in the yeasted dough samples, which were attributed to variation in fermentation time during mixing to peak torque at different speeds. While SAOS results did not show differences due to mixing speed, they did detect differences between the yeasted and nonyeasted dough formulations, as well as significant differences (P < 0.01) between yeasted doughs mixed in the two different mixers. CONCLUSION: The results indicate that known differences in the distribution of elongational and shear flows in the two mixers impact the development of dough structure during mixing. Copyright © 2008 Society of Chemical Industry     

Dynamic rheology of wheat flour dough. I. Non‐linear viscoelastic behaviour

Controlled stress rheometry was used to investigate the effects of starch and gluten fractions on the non‐linearity of wheat flour dough. Flour–water dough showed non‐linear viscoelastic behaviour over all stress values in a cyclic stress sweep. The amplitude‐dependent behaviour of the starch and amplitude‐independent nature of the gluten revealed that starch is responsible for the non‐linearity of the flour–water dough system. Adding starch to gluten caused a substantial narrowing of its linear viscoelastic range. © 2002 Society of Chemical Industry     

Chemometric Approach to Characterization of Flour Mill Streams: Chemical and Rheological Properties

The aim of the present study was to utilize chemometric methods (the principal component analysis and hierarchical cluster analysis) for monitoring the certain aspects of flour mill streams quality and their interrelation to selected rheological properties. Thirty-seven flour mill streams were separated from industrial mill of 300 t/day capacity. All flour streams were analyzed for ash, protein, wet gluten, and damaged starch content and rheological properties as determined by Brabender Farinograph, Extensograph, and Amylograph. The obtained results indicated that break, sizing, and reduction flour streams exhibited different rheological behavior in relation to a change in protein, wet gluten, ash, and mechanically damaged starch content within the milling passages. Rheological properties of dough during mixing and kneading as well as during extension were different with regard to the technological phase of milling from which they were extracted. The obtained results could be utilized for selection of certain flour streams in production of special-purpose flours.     

Impact of endogenous constituents from different flour milling streams on dough rheology and semi-sweet biscuit making potential by partial substitution of a commercial soft wheat flour

A flour fractionation-reconstitution procedure was used to study the substitution of a commercial soft wheat flour with gluten, water extractables, prime starch and starch tailing fractions isolated from patent and clear flour streams on dough rheology and semi-sweet biscuit characteristics. Substitution of soft wheat flour with increasing levels of the native patent and clear flour streams raised the dough consistency, hardness and elastic properties as well as the biscuit textural attributes (density, hardness). The dough stickiness of the base flour was also reduced and the biscuits were free of cracks. Gluten isolated from the patent flour had a greater impact on dough consistency, hardness and elastic properties than gluten obtained from the clear flour, likely due to the superior protein quality of the former. Additionally, with increasing gluten levels in the fortified flour there were moderate increases in biscuit density, hardness, and lower crunchiness. The addition of starch tailings produced the largest impact on consistency and hardness of the dough. This fraction also exerted a pronounced effect on biscuit density and hardness, while it lowered crunchiness, presumably due to its higher pentosan content. Overall, the dough rheological properties and biscuit characteristics were controlled by the amount-nature of the fractions added; i.e., besides gluten (amount and quality), other constituents such as pentosans and the overall composition of the flour blends can largely affect the quality of the semi-sweet biscuits.     

稻米-高筋小麦混合粉面团的静态和动态流变学特性

本实验研究了6 种稻米-高筋混合粉面团的静态和动态流变学特性。结果表明,随着稻米粉添加量的增加,在动态流变频率扫描中,混合面团的储存模量（G’）和损耗模量（G’’）整体呈上升趋势,损耗角正切（tan δ）整体呈规律性下降趋势;在静态流变的蠕变松弛实验中,最大蠕变应变量、最大蠕变柔量和瞬时恢复柔量逐渐减小,零剪切黏度和瞬间恢复比率逐渐增加,表明加入稻米粉后面筋蛋白有所稀释,但稻米粉中的淀粉吸水膨胀相互黏附,且与米蛋白相互作用赋予面团更高的弹性模量和更复杂的内部结构。在动态流变的温度扫描中,糊化温度前后混合面团的黏弹性变化明显,G’和G’’曲线类似淀粉糊化曲线,说明生面团加热的过程中,影响其流变学特性的主要成分为淀粉;降温过程中,稻米粉添加量的影响较小,高温区G’和G’’呈规律性增加,温度低于60 ℃后各项流变指标规律性差;在整个降温的过程中样品均具有类固体的性质。     

Effect of Carob Flour Addition on the Rheological Properties of Gluten-Free Breads

In this study, the rheological properties of gluten-free doughs from rice flour containing different amounts of carob flour were investigated. Water added changed in response to the carob amount. Dynamic oscillatory and creep tests were performed in order to gain knowledge on the rheological behaviour of doughs, which is essential for the control of the bread-making procedure and the production of high-quality bread. Simple power law mathematical models were developed in order to evaluate the effect of carob and water added in dough rheological behaviour. Creep data evaluation demonstrates that an increase in water content decreased the resistance of dough to deformation and, therefore, dough strength, whereas carob flour increased the elastic character and structure strength of the dough. This was also found in dynamic oscillatory tests. Increased amounts of carob flour led to an increase in bread dough elastic character since fibre addition elastifies and strengthens the dough structure. Moreover, doughs exhibited a solid-like viscoelastic character, with the storage modulus (G′) predominant over the loss modulus (G″). Dough rheological properties have an important effect on baking characteristics. Rheological experiments and applied mathematical models can provide us with good knowledge of rheological behaviour and dough viscoelasticity prediction. Therefore, dough samples containing carob-to-water ratios of 10:110 and 15:130 can be considered to possess a balance between the viscous and elastic properties compared to the other samples.     

Effect of β‐Glucan–Rich Barley Flour Fraction on Rheology and Quality of Frozen Yeasted Dough

Research has shown that prolonged frozen storage of bread dough reduces the quality of the end product. In this study, the effect of air‐classified barley flour fraction rich in β‐glucan (approximately 25%) on rheology and quality of frozen yeasted bread dough was investigated. Wheat flour (W) was replaced by air‐classified barley flour fraction (B) at 10% without or with 1.4% vital gluten to produce β‐glucan enriched barley dough (WB) or barley dough plus gluten (WB + G). Dough products were stored at ?18 ºC for 8 wk and their rheological properties were investigated weekly. During frozen storage dough extensibility increased, while elastic and viscous moduli decreased. Differential scanning calorimeter and nuclear magnetic resonance data indicated that WB and WB + G dough products contained approximately 10% less freezable water and 9% more bound water compared to the control dough (W). β‐Glucan enriched dough also exhibited less changes in gluten network as shown by SEM photographs. The addition of air‐classified barley flour fraction at 10% in frozen dough reduced deterioration effects caused by frozen storage via minimizing water redistribution and maintaining rheological properties of frozen dough.     

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.     

黑玉米全粉对小麦面团流变学特性及酥性饼干品质的影响

为了拓宽黑玉米全粉在烘焙食品领域的应用,将黑玉米全粉以0~50%的比例替代强中筋小麦粉,利用黏度仪、粉质及拉伸仪等研究黑玉米全粉替代对小麦粉理化特性及面团热机械特性的影响;利用质构仪、感官评价研究黑玉米全粉替代对酥性饼干品质特性的影响。结果表明,黑玉米全粉的加入对面筋网络结构起到阻隔和断裂作用,湿面筋含量及沉降值分别下降了73.2%、71.0%,面团筋度显著降低。黑玉米全粉替代显著改变了面团的流变学特性,面团形成时间、稳定时间下降,弱化度升高;拉伸能量、延伸度、最大拉伸阻力下降,面团强度、稳定性及耐搅拌性降低,加工性能劣化。黑玉米全粉替代小麦粉酥性饼干的延展因子、质构特性及感官评价指标综合分析结果显示,20%黑玉米全粉添加量的饼干延展因子最大,组织结构细密均匀,表面光滑无裂纹,咀嚼性及硬度最大,酥脆性最好,口感最佳。黑玉米全粉酥性饼干常温下6个月保质期内水分、酸价、过氧化值及菌群总数、大肠菌群、霉菌、致病菌指标都符合国家标准。20%的黑玉米全粉添加量使得小麦粉面团在筋度适当下降的同时获得具有黑玉米风味、口感较好的酥性饼干,该研究可为黑玉米全粉在食品加工行业的应用提供理论依据。     

抗性淀粉对面粉品质及面团流变学特性影响研究

探讨抗性淀粉对小麦粉流变学特性的影响。分别考察了其对高筋粉、中筋粉的粉质特性、拉伸特性和糊化粘度特性的影响,结果表明,抗性淀粉的添加在一定程度上影响了小麦粉的流变学指标和面粉品质。具体表现为面团稳定时间和粉质评价值降低,弱化度增加,延伸度与拉伸曲线面积降低。抗性淀粉的添加使高筋粉的糊化温程升高,糊化时间延长,对中筋粉的糊化温程和时间影响较小。     

Rheological and Microstructural Study of Wheat Doughs Partially Replaced with Mesquite Flour (<Emphasis Type="Italic">Prosopis alba</Emphasis>) and Added with Transglutaminase

The incorporation of different flours into wheat bread may pursue different objectives, such as increasing the nutritional quality of the products or the recovery of flour with little use in the industry. The “mesquite flour” (MF) is rich in sugar, fiber, and protein and is an interesting additive to wheat flour in baking. In this study, we used crude and thermally processed bread dough formulations of wheat flour (WF), replacing 15, 25, and 35% with mesquite flour. Furthermore, each formulation was tested for two levels (0.01 and 0.1%) of the enzyme transglutaminase (TG). Dough rheology was studied by small amplitude oscillatory compression tests, and the microstructure was analyzed by laser confocal microscopy using fluorescein isothiocyanate and rhodamine B as fluorophores. It was concluded that the incorporation of mesquite into the dough resulted in changes in the structure, as evidenced by the increase in tan δ, microscopic observations (loss of the filamentary and cross-linked gluten structure), and by the increase in the gelatinization temperature. The addition of TG led to dissimilar effects on doughs, depending on the formulation (wheat/mesquite content), but most encouraging results indicate the recovery of the structure, evidenced by a reduction in tan δ and the generation of a more filamentary structure in the dough with a higher content of mesquite flour. However, the effect of TG addition on “processed dough” was attenuated and the viscoelastic matrix of gluten did not recover.     

Comparison of uniaxial/biaxial extensional rheological properties of mixed dough with traditional rheological test results: relationship with the quality of steamed bread

The formula and preparation of steamed bread are different from those of western bread. The extensional rheological behaviour plays a key role in the development of steamed bread dough. However, there are inadequate studies on the rheological properties of mixed dough with yeast. In this study, the relationship between properties of dough in the presence or absence of yeast was elucidated. Besides, the flour characteristics and quality of steamed bread prepared from different wheat varieties were evaluated. The uniaxial/biaxial extensional rheological properties of wheat dough were compared with traditional rheological test results. Large deformations in the extensional properties were measured by Extensograph and the Kieffer extensibility rig, while the biaxial extension was quantified using uniaxial compression. These characteristics of dough and flour correlated with each other in different ways. Correlation analysis illustrated that the uniaxial extensional rheological properties of dough with yeast better indicated the quality of the steamed bread. Moreover, the total work for breakage of the dough with yeast was the best predictor for specific volume of steamed bread. The texture-based properties of steamed bread showed correlation with biaxial extension viscosity. The rheological tests provide useful information for evaluating wheat flour and steamed bread quality.     

Gluten–starch interface characteristics and wheat dough rheology—Insights from hybrid artificial systems

Referring to the total surface existing in wheat dough, gluten–starch interfaces are a major component. However, their impact on dough rheology is largely unclear. Common viewpoints, based on starch surface modifications or reconstitution experiments, failed to show unambiguous relations of interface characteristics and dough rheology. Observing hybrid artificial dough systems with defined particle surface functionalization gives a new perspective. Since surface functionalization standardizes particle–polymer interfaces, the impact on rheology becomes clearly transferable and thus, contributes to a better understanding of gluten–starch interfaces. Based on this perspective, the effect of particle/starch surface functionality is discussed in relation to the rheological properties of natural wheat dough and modified gluten–starch systems. A competitive relation of starch and gluten for intermolecular interactions with the network-forming polymer becomes apparent during network development by adsorption phenomena. This gluten–starch adhesiveness delays the beginning of non-linearity under large deformations, thus contributing to a high deformability of dough. Consequently, starch surface functionality affects the mechanical properties, starting from network formation and ending with the thermal fixation of structure.     

Effect of β-Glucan Concentrate on the Water Uptake,Rheological and Textural Properties of Wheat Flour Dough

The effects of the addition of β-glucan concentrate (2.5–10 g/100 g flour) and water (58–70 mL/100 g flour) on the rheological and textural properties of wheat flour doughs were studied. Various empirical (farinograph, extensograph, dough inflation, and dough stickiness) and fundamental rheological tests (oscillatory and creep-recovery) were employed to investigate composite dough structure and an attempt was made to correlate the data obtained from different instrumental measurements. The water absorption increased with the addition of β-glucan concentrate into wheat flour. An increase in mixing time and stability were recorded upon addition of β-glucan concentrate (≤ 5 g/100 g flour), and the extensibility decreased at similar condition. The composite dough exhibited predominating solid-like behavior. The mechanical strength, dough stickiness, the peak dough inflation pressure decreased with increasing water content but those parameters increased with β-glucan concentrate incorporation within the studied concentration range. Creep-recovery tests for 5 g β-glucan concentrate/100 g flour doughs recorded less resistance to deformation with an increase in water level and data were well described by the Burger model. Thermal scanning of doughs revealed that the protein denaturation peak was significantly influenced by water content, and the values were ranged between 110 and 124°C. Significant relationships between empirical and fundamental rheological testing methods were found.     

小麦胚中脂类对小麦粉品质的影响

按一定梯度向小麦粉中添加同种小麦提取的麦胚所制成的胚芽油,测定白度、降落数值、湿面筋含量、干面筋含量及面团流变学特性,并做面条质构及感官评价实验,研究麦胚脂类的添加对小麦粉、面团及面条品质的影响.实验表明,麦胚脂的添加对小麦粉干、湿面筋含量、降落数值没有影响;与白度、吸水率、延伸度呈显著线性负相关;与形成时间、粉质质量指数、拉伸面积、最大拉伸阻力、最大拉伸比呈显著正相关.在一定范围内(0%～6%)面条感官评价总评分随着麦胚脂添加量增大而增大,超过此范围则正好相反;在6%添加量时,面条感官综合评分最高.     

Non-linear creep-recovery measurements as a tool for evaluating the viscoelastic properties of wheat flour dough

Creep-recovery measurements were used to analyze the non-linear viscoelastic properties of wheat flour. First the effect of creep time, recovery time and shear stress was investigated on the non-linear viscoelastic properties of Bussard dough. The Burgers model was fitted to the creep and recovery curves. A linear increase of maximum creep compliance was observed with increasing creep time. On the other hand, maximum recovery compliance remained constant but an increase of the retardation time was observed which indicates a slower recovery. A recovery time of 10 min seemed to be sufficient to obtain most of the recovery. Maximum creep compliance increased proportionally with increasing shear stress until a plateau was reached. Maximum recovery was constant between 100 and 500 Pa but the speed of the recovery increased as shear stress increased. Finally, the optimised creep-recovery methodology was used to analyze the non-linear viscoelastic properties of 17 pure wheat cultivars. By applying principal component analysis, it was possible to identify three groups of wheat cultivars with similar rheological properties and bread volumes.