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.     

Small and large deformation rheology for hard wheat flour dough as influenced by mixing and resting

ABSTRACT:  The effects of mixing and resting on the physicochemical properties of doughs prepared with strong and weak hard wheat flours were investigated, specifically concerning aspects related to their rheological behavior and molecular mobility. Small deformation dynamic tests showed that, during the initial resting period, the complex modulus G * decreased and phase angle decreased for undermixed dough, whereas overmixed dough showed opposite trends. G * values for optimally mixed dough did not vary during the resting period investigated. This was more obvious for the strong dough. Large deformation tests more clearly showed differences among optimal, under-, and overmixed dough, and also between doughs prepared with strong and weak flour. Optimally mixed dough exhibited the highest peak stress and strain for both samples. In addition, the peak stress of dough prepared with the strong flour was higher than that of dough prepared with weak flour. Inconsistent results between small and large deformation tests implied that small and large deformation tests reflected different structural aspects of dough. NMR measurements were performed to estimate the relaxation properties of the sample upon resting. Decreased water mobility during resting, indicated by decreasing T ₁ relaxation time, was possibly attributed to increasing molecular interactions caused by continued hydration. Evidence of additional molecular interactions created by mixing was also observed.     

马铃薯全粉对比萨饼底加工工艺及品质的影响

研究马铃薯全粉对比萨面团流变学特性、发酵能力和比萨饼底质构特征、感官品质的影响。结果表明:马铃薯全粉能提高小麦粉的吸水率,缩短面团的形成时间,但会导致比萨面团的稳定时间缩短,弱化度增加;马铃薯全粉的添加量与面团的拉伸阻力、延伸度、最大拉伸比例和拉伸面积呈极显著负相关;马铃薯全粉能够提高面团的发酵能力和弹性,但会导致比萨饼底的硬度增加,感官品质略有下降,因此综合考虑确定马铃薯全粉的最佳添加量为15%;并进一步通过单因素和正交试验确定马铃薯比萨饼底的最佳原料配方为马铃薯全粉添加量15%、加水量60%、酵母添加量1.2%;在最佳原料配方的基础上确定马铃薯比萨的最佳工艺条件为醒发温度38℃、醒发湿度75%、醒发时间30 min、烘烤温度200℃、烘烤时间15 min,所得比萨的硬度为4 166.493 g,感官品质最佳。     

不同特性乳化剂对面团流变学性质的影响

对添加硬脂酰乳酸钠(SSL)、甘油单硬脂酸酯(DMG)、聚氧乙烯(20)失水山梨醇单硬脂酸酯(polysorbate60)的面团流变学特性进行研究,结果显示,虽然基本脂肪酸组成相同,但3种乳化剂对面团形成时间、面团稳定性、面团弱化度、抗拉伸强度等基本性质的影响有很大差异.高质量分数的DMG对面团有弱化倾向,添加polysorbate60可以得到面团形成的时间最长和最好的面团稳定性;添加SSL和polysorbate60对面团抗拉伸强度有不同程度的提高,而且SSL在较长的面团混揉时间能起到最好作用.不同剂量的乳化剂对面团流变学性质的影响也不相同.     

甘薯泥对面团流变特性及馒头品质的影响

利用粉质仪、拉伸仪、质构仪和色差计研究甘薯泥对面团流变特性及馒头品质的影响。结果表明,随着甘薯泥添加量的增加,面团吸水率、面团形成时间、稳定时间及粉质指数逐渐降低,弱化度增加;面团的拉伸曲线面积、拉伸阻力、拉伸比增大,延伸度降低,且醒发时间越长,其变化趋势越大。与白面馒头相比,甘薯泥的加入使馒头的比容、感官评分降低,胶黏性增大,馒头的亮度下降,色泽变暗,馒头具有浓郁的甘薯香味。     

不同磨粉方法对荞麦面团流变学性质的影响

为研究不同磨粉方法对荞麦面团流变学性质的影响,分别采用石磨、高速万能粉碎机及湿磨三种磨粉方法制得荞麦粉。然后测定由上述荞麦粉制备的荞麦面团的热机械学特性、拉伸特性、质构特性及应力松弛行为。结果表明:与干磨荞麦面团相比,湿磨荞麦面团具有显著较低的面团形成时间和稳定时间以及显著较高的蛋白弱化度,但磨粉方法对淀粉糊化特性影响较小。湿磨荞麦面团的拉断距离低于干磨荞麦面团的拉断距离,但其硬度、黏着性、弹性和胶着性显著高于干磨荞麦面团。此外,湿磨荞麦面团与干磨荞麦面团相比具有显著较高的残余应力和显著较短的松弛时间。不同磨粉方法会导致荞麦面团流变学性质产生差异,面团流变学性质的差异将满足不同的加工需求。     

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.     

Structural and farinographic changes during mixing of a yeast sweet dough

Sweet dough requires longer mixing time than salty or white pan bread doughs to reach a developed stage. Although many studies have dealt with the effect of mixing time on dough, few have referred to yeast sweet doughs. The aim of this study was to evaluate if the changes in dough microstructure during different stages of mixing were the same between sweet pan bread and white pan bread, using as control a flour water system. Scanning electronic microscopy (SEM) and some bread characteristics were used as evaluation parameters. Doughs were prepared in a Brabender Farinograph instrument. Different mixing times were used for each formulation, which correspond to common farinographic parameters such as: arrival time, peak time, departure time, etc. Farinographic consistency was evaluated at those times. Results showed that sweet dough farinogram was quite different from those obtained from the other two samples; it starts with a low consistency value (260 BU), and after 8 min of mixing it began to increase until almost reaching the 500 BU line; then the graphic follows the classical curve. Larger products were obtained from arrival time to departure time for both formulations. SEM showed that as mixing proceeds the dough structure opens, changing its appearance from a compact structure at the beginning to a very open one at the end of the mixing process. SEM also showed that the process of mixing is the same for the two samples and control; however, the time needed to reach each stage was different among samples. Farinogram can be used to get information about mixing behavior of yeast sweet doughs. The study of mixing can be easier using sweet dough formulations because it was possible to get more points between the onset of mixing and full dough development, and the process was very similar no matter the formulation.     

Rheological properties of wheat flour doughs I.—Method for determining the large deformation and rupture properties in simple tension

A method and an apparatus are described for determining the large deformation and rupture properties of wheat flour doughs in simple tension. Dough rings are submerged in a liquid of matching density to prevent the dough from deforming under its own weight and are stretched at constant rates of extension until rupture occurs. Stress-strain curves obtained at different temperatures and extension rates on doughs prepared from a medium strength flour and a weak flour are presented, and the effects of rest period, mixing time, and mixing atmosphere on dough properties are discussed.     

STRAIN HARDENING OF DOUGH AS A REQUIREMENT FOR GAS RETENTION

Mechanisms that can be responsible for the ability of wheat flour doughs to retain gas are discussed. It is concluded that the relevant types of physical instabilities are Ostwald ripening (disproportionation) and coalescence of gas cells. The extent of Ostwald ripening is probably primarily controlled by surface rheological properties; it certainly affects crumb structure, but it cannot explain the differences in gas retention among doughs from various cereals or various wheat cultivars. It is argued that surface forces only provide a stabilizing mechanism for dough films between gas cells, i.e., against coalescence, for films that are much thinner than the diameter of a starch granule. It is concluded that variation in the potential for gas retention among wheat flour doughs is largely due to variation in bulk rheological properties. We propose a new rheological criterion for the extensibility of dough films between gas cells (and thereby for gas retention) that is based on the strain hardening of the dough in biaxial extension exceeding a specific lower limit. The criterion is translated into measurable parameters. Preliminary experiments on doughs with poor and with satisfactory baking performance illustrate its potential importance.     

The effect of lipoxygenase action on the mechanical development of wheat flour doughs

The mechanical development of dough has been followed by measurement of the relaxation time of dough samples after mixing to various levels of work input. Parallel determinations of free and bound lipid have also been made. When doughs were mixed in air, addition of full-fat, enzyme-active soya bean flour (subsequently referred to as “soya flour”) resulted in an increase in relaxation time, particularly at higher work levels. The magnitude of this improvement increased with increasing work input and was dependent on the rate of work input. Addition of soya flour also enabled a higher level of mechanical work to be introduced before dough breakdown occurred. When doughs were mixed under nitrogen, or when the soya flour was heat denatured, no change in the rheological properties compared with the respective control doughs was found. The release of bound lipid, which occurred during dough development in air in the presence of soya flour, could also be induced by adding purified lipoxygenase to the dough, together with linoleic acid as a substrate. This resulted in rheological changes similar to those observed using soya flour. However addition of enzymically pre-peroxidised lipid to doughs mixed in nitrogen was without effect on relaxation times. These findings suggest that lipid release is linked with structural changes in dough protein and provide further support for a mechanism of coupled oxidation of protein -SH groups by lipoxygenase.     

Effect of inulin on rheological properties of soft and strong wheat dough

The influence of inulin with different degrees of polymerisation (DP) on the farinograph characteristics, extensograph parameters and fermentation rheological properties of soft and strong wheat dough was explored. The results showed that the addition of inulin can reduce the water absorption of doughs, and inulin with lower DP had more significant effect and the influence on the soft dough was stronger than the strong dough. Inulin can enhance mechanical properties of the gluten network and improve the resistance to mixing of soft dough. The extensibility of doughs decreased with increasing inulin. Inulin increased the resistance to extension of soft dough; however, it is reverse for strong dough. Adding inulin significantly increased the volume of gas production and the maximum expansion height of doughs, and the effect of inulin with lower DP was more prominent. Additionally, the gas‐holding capacity of doughs was enhanced by inulin.     

Ultrasonic Investigation of the Effect of Vegetable Shortening and Mixing Time on the Mechanical Properties of Bread Dough

ABSTRACT:  Mixing is a critical stage in breadmaking since it controls gluten development and nucleation of gas bubbles in the dough. Bubbles affect the rheology of the dough and largely govern the quality of the final product. This study used ultrasound (at a frequency where it is sensitive to the presence of bubbles) to nondestructively examine dough properties as a function of mixing time in doughs prepared from strong red spring wheat flour with various amounts of shortening (0%, 2%, 4%, 8% flour weight basis). The doughs were mixed for various times at atmospheric pressure or under vacuum (to minimize bubble nucleation). Ultrasonic velocity and attenuation (nominally at 50 kHz) were measured in the dough, and dough density was measured independently from specific gravity determinations. Ultrasonic velocity decreased substantially as mixing time increased (and more bubbles were entrained) for all doughs mixed in air; for example, in doughs made without shortening, velocity decreased from 165 to 105 ms⁻¹, although superimposed on this overall decrease was a peak in velocity at optimum mixing time. Changes in attenuation coefficient due to the addition of shortening were evident in both air-mixed and vacuum-mixed doughs, suggesting that ultrasound was sensitive to changes in the properties of the dough matrix during dough development and to plasticization of the gluten polymers by the shortening. Due to its ability to probe the effect of mixing times and ingredients on dough properties, ultrasound has the potential to be deployed as an online quality control tool in the baking industry.     

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     

Correlation Between Fracture of Semi-sweet Hard Biscuits and Dough Viscoelastic Properties

Semi-sweet hard dough biscuits were considered in the present work which aims at assessing whether biscuit failure mode and dough viscoelastic properties, which depend on the resting time after mixing, can be correlated to one another. Uniaxial compressions were performed on rested biscuit doughs to determine biaxial extensional viscosities. The experimental data seemed strongly dependent on the compression rate in the 1-20 mm/min range of crosshead speed. The stress growth trend observed for doughs of different resting time showed that the extent of structural recovery increased with resting. The rheological behuviour of dough under higher extensional deformation was evaluated by means of tensile and tensilerelaxation tests, the result of which can be directly related to the sheeting extensional deformation. These data confirmed the picture of dough structural recovery. Rheological investigations were coupled with DSC determinations of the glass transition temperature, The higher Tg found for rested doughs was tentatively attributed to gluten protein polymerisation. It was finally shown that the failure mode of biscuits changes with the resting time after mixing: the longer the rest, the less the biscuit strength.     

Semi-Sweet Biscuits: 2. Alternatives to the Use of Sodium Metabisulphite in Semi-Sweet Biscuit Production

The influence of sodium metabisulphite (SMS) and other gluten-modifying agents on the performance of a commercial biscuit flour in the production of semi-sweet biscuits has been studied. Use of a proteolytic enzyme as a gluten-modifying agent resulted in a dough with a longer mixing time than other doughs, partly as a result of mixing to a higher temperature. The extrusion time of doughs containing the proteolytic enzyme was closest to the extrusion time of doughs containing SMS. Doughs containing SMS or proteolytic enzyme produced significantly shorter extrusion times than doughs containing l -cysteine hydrochloride. Dynamic oscillatory measurements showed that for doughs made at a constant water level the lowest elastic and viscous moduli were produced by doughs containing sodium metabisulphite. Doughs containing the other gluten-modifying agents produced stronger elastic properties than those containing SMS but weaker elastic properties than doughs containing no gluten-modifying agent. The hardness of the semi-sweet biscuits produced was found to be reduced by a weakening of the rheological properties of the dough. All gluten-modifying agents reduced dough piece contraction in length during processing, although SMS was the most effective. A decrease in dough piece length during processing caused an increase in dough piece thickness and width. Use of a proteolytic enzyme or the enzyme and l -cysteine hydrochloride in combination, as gluten-modifying agents, produced biscuits closest in quality to those produced from doughs containing SMS.     

蒙古栎橡子-小麦混粉的流变学特性

将蒙古栎橡子粉与小麦粉按不同的比例混合,利用布拉本德粉质仪与拉伸仪测定蒙古栎橡子-小麦混粉面团的流变学特性,并对混粉中的理化指标与混粉面团流变学参数之间进行相关性分析,探讨蒙古栎橡子粉对小麦粉品质的影响。结果表明：随着橡子粉含量增加,混粉的吸水率呈先减小后增大的趋势,面团的形成时间与稳定时间缩短,弱化度提高;所有样品的拉伸阻力与拉伸比例随醒发时间的增长而增大,而混粉面团的延伸度与能量均呈下降趋势;在相同的醒发时间下,拉伸参数随橡子粉添加比例的增加呈先增大后减小的趋势。与混粉面团流变学特性呈高度正相关的理化指标是混粉面团湿面筋及蛋白质的含量。提示不同比例的蒙古栎橡子粉可以显著影响面团的流变学特性。     

The effect of lipoxygenase action on the mechanical development of doughs from fat-extracted and reconstituted wheat flours

The mechanism by which soya lipoxygenase enzyme action improves the Theological properties of wheat flour doughs during mechanical development in air has been investigated further. Free-lipid extraction, reconstitution and replacement experiments have shown that the rheological effect of lipoxygenase action, which is consistent with an oxidative improvement of the dough proteins and may also result in extended mixing tolerance, only occurred in the presence of an oxidisable, polyunsaturated, free-lipid substrate. Addition of this substrate in an oxidised state (produced either by autoxidation or enzyme-oxidation) to doughs mixed from fat-extracted flour under nitrogen resulted only in a small rheological improvement, greater for the autoxidised than the enzyme-oxidised lipid, but in no way comparable with the large rheological effect of lipoxygenase action during dough mixing in air. Furthermore, the presence of an antioxidant, nordihydroguaiaretic acid (NDGA), during dough development, although greatly inhibiting peroxide formation, only marginally impaired the rheological improvement due to lipoxygenase action. Additional evidence is therefore provided for a coupled oxidation mechanism being responsible for the rheological effect, since lipoxygenase-catalysed oxidation actively occurring in the dough during mixing appears to be the fundamental requirement, irrespective of whether the primary oxidation products lead to lipid peroxides or oxidised NDGA.     

Rheological properties of wheat dough supplemented with functional by-products of food processing: Brewer’s spent grain and apple pomace

The physicochemical properties of brewer’s spent grain (BSG) and apple pomace (AP), and their effect on dough rheological properties were investigated. BSG had high protein content and both by-products were found to be high in dietary fibre. The rheological and the pasting properties of dough were significantly altered by the addition of by-products, with the main effects being due to the presence of dietary fibre. The biaxial extensional viscosity was significantly higher for the supplemented doughs; the strain hardening index decreased with increasing the levels of flour substitution. The replacement of wheat flour with the by-products significantly reduced the uniaxial extensibility, while the storage modulus, G″, was found to increase, indicating changes in the structural properties of dough. These changes were reflected in the ability of dough to rise during proofing.