EXAMINATION OF RELATIONSHIPS BETWEEN THE RHEOLOGICAL PROPERTIES AND BAKING PERFORMANCE OF SELECTED SOFT WHEAT FLOURS

Results of farinograph and dough stickiness testing of seven 1BL/1RS positive and five 1BL/1RS negative soft, red, winter wheats (SRWW) were correlated with baking performance data. Biscuit volume was not significantly correlated with any farinograph parameters or with dough stickiness. Significant negative correlations were found between the diameters of cookies baked from SRWW flours and their farinograph percent water absorption, r =−0.825 (P < 0.01) and arrival times, r =−0.476 (P ≤ 0.05). Cake volume was negatively correlated with percent water absorption values of SRWW flours, r =−0.494 (P ≥ 0.05). Dough stickiness was positively correlated with cake tenderness, r = 0.486 (P ≥ 0.05). Significant positive correlations were also found between the cake tenderness of SRWW when grown in one of two locations, Blacksburg, Virginia, and farinograph departure times, r = 0.751 (P ≥ 0.05), and mixing stabilities, r = 0.749 (P ≥ 0.05). The results suggest that although bakers may encounter problems in using 1BL/1RS translocated SRWW flours in cookies because of reduced cookie spread, these flours can be successfully incorporated into biscuits and cakes.     

绿豆-小麦混合粉的流变学和热力学特性研究

以小麦粉、绿豆粉为原料,研究绿豆-小麦混合粉面团的形成特性、流变学特性、热力学特性,为绿豆小麦粉复合食品的加工及品质控制提供参考。结果表明,添加绿豆粉对绿豆-小麦混合粉的物性有显著影响;随着绿豆粉添加量的增加,混合粉面团的吸水率、形成时间、稳定时间、评价值降低、弱化值增加;最大拉伸阻力、延伸度降低;热焓呈非线性降低,糊化温度增加;储能模量、损耗模量减小,黏弹性降低。     

The optimization of a laboratory processing procedure for southern-style Chinese steamed bread

A response surface methodology (RSM) design was used to optimize the laboratory processing procedure for southern-style Chinese steamed bread (SSCSB). A screening test was applied to weak, medium and strong flours to establish critical variables. Consumer preference testing on the eating quality of southern-style steamed bread (SSSB) established a scoring system for quality assessment of this product. For further RSM optimization testing, only the strong and medium flours were used. The following settings were established as optimal laboratory processing procedures for this style of steamed bread: farinograph mixer (300-g bowl; speed 60 rpm); compressed yeast (1.5%); water addition [80% of farinograph water absorption (FWA)]; mixing time (50% of farinograph dough development time (FDDT); fermentation time (150 min); remixing time (180% FDDT); fermentation temperature (32°C); relative humidity (RH; 85%); sheeting time (20 passes); proving time (35 min); steaming rate (155 g of steam m⁻³ min⁻¹); and steam time (20 min). The adequacy of the predictive models generated using the RSM procedure and reproducibility of the method for this style steamed bread were verified.     

Rheological Properties and Bread Quality of Wheat and Rice Starch Composite Flours

Rice starch was added to wheat flour to form different rice composite flours. The rheological characteristics of different mixtures showed a decrease in the farinograph absorption and an increase in mechanical tolerance index when rice starch was added at 40% level. Dough stability, development time, arrival time and over-all farinograph profile scores were decreased. Extensograph data showed an increase in dough deadness and a drop in dough extensibility. Although dough rheology data indicated that the addition of rice starch weakened the dough, bread of acceptable quality was obtained when rice starch was added at 25% level. This should be of interest for development countries where rice is a native crop.     

Functional Properties of Wheat-Bean Composite Flours

Functional properties of wheat flour and its blends with six bean flours at three levels of replacement (10, 20, and 30%) were investigated. Water and oil absorption, foaming capacity and stability, and emulsifying activity and stability increased with increasing levels of bean flours in the blends. Composite flours had higher pasting properties compared to those of wheat flour as measured in the Brabender Viscoamylograph. As the level of bean flour in the composite was increased, farinograph absorption and mixing tolerance index increased, whereas mixing time and dough stability decreased.     

Use of farinograph measurements for predicting extensograph traits of bread dough enriched with carob fibre and oat wholemeal

Farinograph and extensograph tests were applied to determine the effect of carob fibre and oat wholemeal on the rheological properties of wheat flour dough, and characterisation of relationships between the results of the tests was performed. The applied additions of carob fibre (1-5%) and oat wholemeal (5-25%) increased the water absorption of the dough within nearly identical ranges (56-59%). Enrichment with carob fibre made the dough more rheologically stable during mixing compared to dough with oat wholemeal. In the extension test, dough with an admixture of carob fibre was more resistant, but it was less extensible than dough with oat wholemeal.Analysis of relationships of the extensograph traits to the farinograph ones revealed that longer periods of development of dough enriched with the additions under examination involved the formation of a looser dough structure, as a result of which its resistance to extension, ratio number and energy decreased and the dough extensibility increased. Opposite effects were caused by increasing farinograph elasticity and its loss. The degree of softening, negatively correlating with resistance, ratio number and energy, coupled with water absorption or with loss of elasticity, permitted their more accurate prediction. In turn, combining in a regression model of water absorption with development time or with elasticity was the most suitable for predicting dough extensibility.     

不同品种粳米-低筋小麦混合粉体系粉质特性研究

采用市售低筋粉分别与5种粳米粉组成混合粉体系,对其粉质和拉伸特性变化规律,及其与各品种粳米粉的组成成分的相关性进行分析。结果表明:随粳米粉添加量的增加,吸水率以及拉伸比值整体呈上升变化趋势;面团形成时间、稳定时间、评价值以及面团抗拉伸阻力整体略呈下降变化趋势;延伸性呈显著性下降;弱化度整体先升高后降低。当粳米粉添加量不同时,除蛋白质和灰分外的其它组分均与粳米-低筋小麦混合粉面团的各项粉质特性参数指标呈现显著相关性。     

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.     

Separation of bread wheat flours into starch and gluten fractions: effect of water temperature alone or in combination with water to flour ratio

Two different commercial bread wheat flours (BF‐I, 65% extraction and BF‐V, 86% extraction) were separated into gluten and starch milk by making a dough, allowing some time for maturation, dispersing the dough in water and wet sieving/washing. The effect of using of warm water (20–45 °C) for dough making and washing on separation was studied for BF‐I flour at 640 g kg^?1 water to flour ratio of and 300 s maturation time, and the separation was found to improve with increase in temperature. The combined effects of water temperature (20–50 °C) and water to flour ratio (640–780 g kg^?1 for BF‐I and 620–870 g kg^?1 for BF‐V) were studied at 600 s maturation time. The quantities and dry matter contents of the gluten fraction and starch milk were measured; a sample of starch milk was centrifuged to obtain decantate, tailing and prime starch fractions, and the dry matter contents of each were determined. All the dried samples were also analysed for protein content, and the fractional recoveries of dry matter and protein in the gluten fraction, prime starch, tailings and decantate were calculated. The results indicated the optimum point for BF‐I flour to be the combination of optimum farinograph water absorption and 40 °C. BF‐V showed very poor separation behaviour within the ranges studied. At the optimum farinograph water absorption the use of warm water for dough making and 20 °C water for washing steps was also tried, but no significant improvement over the 20 °C results was obtained. © 2002 Society of Chemical Industry     

Dough properties and baking characteristics of white bread,as affected by addition of raw,germinated and toasted pea flour

Thermal and non-thermal processing may alter the structure and improve the techno-functional properties of pulses and pulse flours, increasing their range of applications in protein-enhanced foods. The effects of germination and toasting of yellow peas (Pisum sativum) on flour and dough characteristics were investigated. Wheat flour was substituted with raw, germinated and toasted pea flour (30%). The resulting bread-baking properties were assessed. Toasting increased dough water absorption and improved dough stability compared with germinated and raw pea flour (p < 0.05). This resulted in bread loaves with comparable specific volume and loaf density to that of a wheat flour control. Significant correlations between dough rheological properties and loaf characteristics were observed. Addition of pea flours increased the protein content of the breads from 8.4% in the control white bread, to 10.1–10.8% (p < 0.001). Toasting demonstrated the potential to improve the techno-functional properties of pea flour. Results highlight the potential application of pea flour in bread-making to increase the protein content.     

Comparison of lipid effects on structural features of hard and soft wheat flour proteins assessed by front-face fluorescence

Front-face fluorescence was used to assess changes in the structural features of proteins in wheat flour dough upon addition of different exogenous lipids. Structural changes resulting from the solvation of proteins and from the mechanical deformation of proteins in dough or dough containing lipids were measured. The effects of lipid type and addition on changes in overall protein surface hydrophobicity were estimated by titrating soft and hard wheat flours, mixed with water and varying the lipid levels, with increasing concentrations of the fluorescence hydrophobic probes 1,8 anilino-napthalene-sulphonate (ANS) and thioflavin T. The lipid type and level modified the exposure of the probe to the solvent. The effects of lipids were more apparent with soft wheat flour having low-affinity hydrophobic sites on the protein surface. The dough was then characterized upon consistent mixing and physical modification in the farinograph at constant water and ANS/thioflavin T concentration, while varying the type and amount of lipids. Lipid-dependent shifts toward longer wavelengths in the probe fluorescent emission with low-protein flour suggest differences in protein coating effects related to lipid structure and protein quality.     

添加冻干无花果粉对小麦面粉品质的影响

将冻干无花果粉与小麦粉按不同的比例混合,研究冻干无花果粉添加量对面粉特性的影响。混合粉的糊化和粉质特性分别使用快速黏度分析仪、粉质仪等进行测定;面筋的超微结构则利用扫描电子显微镜进行观察。结果表明：随着冻干无花果粉添加量的增加,混粉的沉淀值、降落值、峰值黏度、低谷黏度、最终黏度、稀懈值和反弹值均呈显著下降趋势;面团粉质参数除弱化度以外,其余参数均随添加物的增多而降低;扫描电子显微镜显示,冻干无花果粉的添加阻碍了面筋网络的形成。与1%添加量时的面团结构相比较,添加3%冻干无花果粉对面筋网络造成了更大的破坏。因此,冻干无花果粉的添加,改变了面粉的糊化特性、粉质特性及面筋超微结构。     

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.     

OBJECTIVE MEASUREMENTS OF THE CONSISTENCY OF CHAPATI DOUGH USING A RESEARCH WATER ABSORPTION METER

A Research Water Absorption Meter (RWAM) was adapted to measure the consistency of chapati doughs made from whole wheat flour (WWF). Doughs of optimum consistency were characterized by an extrusion time of 60 ± 5 s when extruded with an additional weight of 2 Kg, after resting the dough for 20 min. The RWAM consistency was Significantly correlated to the farinograph consistency ( r =+ 0.97), as well as to hardness ( r =+ 0.96) recorded on a General Foods Texturometer. The water required to prepare a chapati dough of this consistency can be determined from a semi-logarithmic plot of the extrusion time of doughs of varying water contents against the water added. Chapati water absorption can be determined by multiplying the farinograph water absorption measured at 500 B. U. by a factor of 0.85, or by adjusting the farinograph consistency to 460 ± 20 BU at a lever setting of 1:3 instead of 1:1. A multiple regression equation, derived for predicting chapati water absorption based on particle size, damaged starch, and protein content, accounted for 88% of the variation.     

Effect of Wheat Bran Particle Size on Dough Rheological Properties

Commercial hard red spring, hard red winter, soft white and durum wheat brans were used to investigate the effect of wheat bran particle size on the rheological properties of doughs. Wheat brans were first coarsely ground and passed through a bran finisher to remove additional endosperm and aleurone layers. These processes increased total dietary fibre content and decreased starch content of the wheat bran samples. Three particle size distributions, for each wheat bran class, were obtained by further grinding (not by sifting) of the bran samples by different experimental mills. Coarse bran can retain significantly more water than medium or fine bran as measured by a centrifuge method, but bran particle size had no significant effect on dough water absorption. Addition of wheat bran into bread dough systems increased dough water absorption rate, reduced mixing time and decreased dough mixing tolerance as measured by farinograph. Fine particle size wheat bran decreased dough mixing tolerance and reduced mixing time compared to coarse bran. Dough containing fine particle size bran exhibited more strength than dough containing coarse bran after a 180-min rest period as measured by the extensigraph. © 1997 SCI.     

Rheological and Microstructure Characterization of Composite Dough with Wheat and Mesquite (Prosopis spp) Flours

Rheological behavior and microstructural characteristics of composite dough with wheat and mesquite flours (from Prosopis alba) were analyzed by response surface methodology. A central composite design was applied varying proportions of water (50 to 80 g each 100 g wheat flour) and mesquite flour (0 to 70 each 100 g wheat flour). Texture profile analysis showed that increasing the amount of mesquite flour and decreasing the amount of water led to less cohesive and more resilient doughs. Stress relaxation curves were fitted with a Maxwell model and relaxation times were obtained. These parameters resulted higher for those formulations low in mesquite content and high water levels. Composite dough showed a typical viscoelastic behavior with higher elastic moduli (G’) when mesquite flour ratio in the mixture was increased. ¹H-RMN T2 relaxation assays revealed higher mobility in samples with high amounts of water and minimum level of mesquite. A farinograph was adequate to obtain optimum water amounts and showed that addition of mesquite led to less stable dough respect to control wheat dough. By using confocal laser scanning microscopy with fluorescent probes rhodamine B and fluoresceine isothiocyanate, a poor gluten network development or protein aggregation was observed when water contents were far from optimum.     

Bread Quality of Wheat Flour by Near-Infrared Spectrophotometry: Feasibility of Modeling

Commercial bakeries need a means to measure the dough-handling and bread-making functionalitv of wheat flour during processing. The feasibility of using near-infrared (NIR) reflectance spectrophotometry for such measurement was examined. Flour from hard red spring and hard red winter wheat were tested for: water absorption, dough mixing time, dough mixing tolerance, loaf height, internal grain appearance, and overall bake score. The ability of NIR to measure protein level, and/ or starch damage, as well as positive relationships between the two and water absorption, probably made it successful for modeling water absorption. Models for the remaining five indices were less accurate due to the complexity of interactions between protein, starch, and lipids, and inadequate instrument sensitivity.     

Indian Wheat Cultivars: Correlation between Quality of Gluten Proteins,Rheological Characteristics of Dough and Tandoori Roti Quality

Physico-chemical, rheological characteristics and quality of tandoori roti were determined for whole wheat flours from eight commercial wheat cultivars grown at one location. Tandoori roties baked from these flours indicated wide differences in baking performance. Among the varieties, Cpan-3004, GW-180 and K-8804 and WL-1562 were found suitable for the preparation of tandoori roti. These four varieties had higher water absorption capacity (718–735 ml kg^-1) when measured in a farinograph at an optimum tandoori dough consistency of 400 BU. The doughs from these varieties also had higher cohesiveness (0·38–0·45) and extensibility (114–121 mm) than other varieties. Total protein, gluten as well as total glutenin (soluble and insoluble) contents were found to be maximum in these four varieties. Varieties having Glu-1 score of 6 were found to be more suitable for roti preparation. The prediction equation derived for correlating total protein and total glutenin in flour with overall sensory score of roti was found highly significant (R² = 0·92). The results suggest that the medium hard wheats are suitable for the preparation of tandoori roti. © 1997 SCI.     

Biscuit-Making Quality Prediction Using Heritability Estimates and Correlations

The aim of this study was to predict biscuit-making quality by using correlations between and, heritabilities of, the most important soft wheat quality characteristics. A full diallele cross was made between six spring wheats. The parents and 30 F ₁ hybrids were used as experimental material. Percentage vitreous kernels, breakflour yield, farinograph absorption, farinograph development time and alkaline water retention capacity were highly heritable and were also significantly correlated with sugar-snap biscuit diameter. Selection for these characteristics should lead to improvement of biscuit-making quality. In general, softer kernels and a weak dough with a low water absorption were desirable for good biscuit-making quality.     

The estimation of rheologically important thiol and disulphide groups in dough

Quantitative methods are presented for distinguishing rheologically-important thiol and disulphide groups of wheat dough from those which are unimportant. The determinations are carried out in the farinograph and the use of extracting solvents is completely avoided. Dithiothreitol and N-ethylmaleimide are used as respective titrants of disulphide and thiol groups. Less than 4% of the total disulphide is involved in determining development time; 11 to 13% is involved in the resistance to mixing. About 25 to 35% of the total thiol is involved in both development and tolerance to mixing. A positive relationship between the content of rheologically-important disulphide and development time has been shown in flours from several varieties of wheat. It was further found that the addition of iodate can rapidly increase the resistance to mixing of a partly reduced dough. The nature of the rheologically-important thiol and disulphide groups is discussed in relation to current knowledge of their distribution among large and small molecules, their importance in maintaining structure and their involvement in thiol-disulphide exchange reactions during mixing.