Grain and milling characteristics and their relationship with selected mixogram parameters in hard red bread wheat

Breeders in South Africa are faced with the problem that quality testing is only done in advanced phases of the bread wheat breeding programme when enough seed is available. This means that lines not meeting quality requirements of the South African industry for cultivar release are only discarded during the advanced breeding phases. The aim of this study was to determine relationships between grain and milling characteristics and mixogram parameters and to determine whether these characteristics can be used for selection of acceptable mixogram parameters and vice versa. A mixograph with Mixsmart software was used to analyse 10 bread wheat cultivars, in four replications at three different locations. Thirteen mixogram parameters were used to determine correlations with important grain and milling characteristics. Highly significant correlations were observed between mixogram parameters and grain as well as milling characteristics, although not with hectolitre mass, thousand kernel mass, vitreous kernels, falling number or flour colour. Multiple coefficient of determination was low to moderate for grain characteristics and low for milling characteristics as independent variables in explaining the variation in several mixogram parameters. In spite of the highly significant correlations, grain and milling characteristics explained little of the variation in mixogram parameters in this study.     

Solvent retention capacity and swelling index of glutenin in hard red wheat flour as possible indicators of rheological and baking quality characteristics

To overcome the cost and expense of milling and baking hundreds of samples in wheat breeding programs, cereal chemists have developed various rapid predictive tests for end-use quality assessment. In this study, five small-scale rapid tests, including Solvent Retention Capacity (SRC) and Swelling Index of Glutenin (SIG), were compared for viability and accuracy to determine end-use quality using small quantities of flour. The tests were applied on commercial hard red spring and hard red winter wheat cultivars from two of the three main production regions in South Africa. Rheological and bread-baking characteristics were related to results of the rapid tests. Highly significant cultivar differences were seen for all rheological and baking-related characteristics, and SRC and SIG parameters, with a strong genotype effect. The environment effect was also highly significant across regions, especially for flour protein content (FPC), which affected the rheological and baking-related characteristics differently across the regions. Correlations among SRC, SIG, rheological, and baking quality-related parameters were highly significant, but inconsistent for the two production regions. Only lactic acid SRC and SIG correlated consistently with the rheological and baking quality-related characteristics in both production regions.     

Comparison of predictions of baking volume using large deformation rheological properties

Three large deformation rheological tests, the Kieffer dough extensibility system, the D/R dough inflation system and the 2 g mixograph test, were carried out on doughs made from a large number of winter wheat lines and cultivars grown in Poland. These lines and cultivars represented a broad spread in baking performance in order to assess their suitability as predictors of baking volume. The parameters most closely associated with baking volume were strain hardening index, bubble failure strain, and mixograph bandwidth at 10 min. Simple correlations with baking volume indicate that bubble failure strain and strain hardening index give the highest correlations, whilst the use of best subsets regression, which selects the best combination of parameters, gave increased correlations with R²=0.865 for dough inflation parameters, R²=0.842 for Kieffer parameters and R²=0.760 for mixograph parameters.     

春小麦品种高分子量谷蛋白亚基与品质的关系

选用甘肃省河西地区种植的57个春小麦品种。在已经分析HMW—GS组成的基础上。测定了这些品种的理化特性和面团流变学特性。对这些品种的HMW—GS和品质性状的变异情况、HMW—GS与品质性状之间的关系、具有不同HMW—GS的品种间品质的差异和同-HMW—GS品种间的品质差异进行了研究。结果表明，Glu-Ⅰ位点的亚基总评分与面筋指数、沉淀值、面团变形功、面团形成时间及稳定时间呈显著或极显著正相关；HMW—GS数目的多少与其品质优劣有关，亚基数目越多，面粉筋力越好；采用不同品质指标评价小麦HMW—GS对品质的贡献，结果表明以变形功的评价排序的意义更明确。     

Dough mixing characteristics measured by Mixsmart software as possible predictors of bread making quality in three production regions of South Africa

South Africa has three wheat production regions, the winter rainfall region where spring wheat is planted; the summer rainfall where winter and intermediate wheat is cultivated; and the irrigation region where spring wheat is grown. The aim of this study was to determine dough mixing characteristics as measured by Mixsmart^® software in these three regions over seasons and locations, and to relate this to important quality characteristics. In the winter rainfall area Mixsmart characteristics were very poor predictors of baking quality, especially of loaf volume, flour protein content and wet gluten content. The best predictors of loaf volume in this region were flour protein content and wet gluten content, which were highly interrelated. In the irrigation area, midline peak value and midline right value were very good predictors of flour protein content, gluten content and loaf volume. Midline peak value was highly correlated with protein content in both the irrigation and summer rainfall areas and was a better predictor than peak time of baking quality. The ideal would be to select several parameters from the mixograph and use them in a multivariate statistical analysis to obtain a more accurate prediction of loaf volume in the irrigation and summer rainfall areas.     

Correlations of the Breadmaking Performance of Wheat Flour with Rheological Measurements on a Micro-scale

For the characterization of wheat quality, micro-extension tests for dough and gluten and a micro-baking test were developed using comparable dough compositions, the same mixing temperature and cultivar-specific mixing times. By means of these methods, the flours of 26 wheat samples were studied for dough development time, maximum resistance and extensibility of dough and gluten and loaf volume of the baked products. Standard methods (rapid-mix-test, gluten index determination) were used for comparison. The results indicated that the rheological properties of dough and gluten as well as the gluten index are correlated higher with the optimised micro-baking test than with the standard baking test. If flour protein or wet gluten content is included in the correlations, the extension test of gluten, which can be performed easily and reproducibly, allows a reliable prediction of the loaf volume obtained by the micro-baking test.     

Rheological properties and baking quality of wheat varieties from various geographical regions

Eight wheat varieties, originating from various geographical regions were examined for their rheological properties during large uniaxial and biaxial extensions and for their baking quality. Extensibility during uniaxial extension as well as biaxial extensional viscosity proved to be significant properties in predicting loaf volume. Multiple regression analysis indicated uniaxial extensibility and biaxial extensional viscosity as best predictors for loaf volume. The varieties with the highest strain hardening index were those of high loaf volume and also fine and soft crumb, whereas varieties of low strain hardening index were of poor baking quality. However, baking behaviour was not completely explained by considering only the strain hardening index. Crumb fineness was also investigated and it was taken into consideration when evaluating the varieties for their baking quality. 3D scatter plots of loaf volume, cell volume, and number of cells in the slice, divided the wheat samples in groups depending on their baking quality and common rheological characteristics were observed for these groups. The samples were also examined for their proofing capacity. Maximum dough height from the rheofermentometer correlated with loaf volume and was affected by rheological properties of the samples.     

Improving the baking quality of bread wheat using rapid tests and genomics: The prediction of dough rheological parameters by gluten peak indices and genomic selection models

The measurement of baking quality by dough mixing and viscoelastic tests is often labor-intensive and time-consuming, thus the possibility to predict these rheological parameters either by rapid tests or genomic selection models based on molecular markers was investigated in this study. A winter wheat breeding population of 128 genotypes was measured for its rheological parameters, gluten peak indices and other rapid test variables in multiple environments. The prediction accuracy of the rheological parameters was assessed in different cross-validation schemes, reflecting scenarios encountered either in food-processing or by plant breeders. Predictions based on gluten peak indices (r = 0.41–0.82) outperformed the other investigated rapid tests in the food-processing scenario. The combination of gluten peak indices with sedimentation value and protein content gave furthermore the overall highest prediction accuracy (r = 0.70). Cross-validation results from the plant breeding scenario revealed that the prediction accuracy of genomic selection models was merely slightly lower (r = 0.42) than using a combination of sedimentation value and protein content (r = 0.44). Merging gluten peak indices with genomic estimated breeding values resulted in a higher accuracy than either method alone (r = 0.52), and was a promising strategy to select for baking quality in wheat breeding.     

国内强筋小麦品种及配麦的面包加工性能研究

为通过合理配麦提升国内优质强筋小麦的面包加工性能,对11种主栽强筋小麦品种进行理化、面团流变学检测及烘焙评价,筛选出综合品质较优、特点不同且互补的三个品种,分析其不同比例配麦对面粉理化特性和面包品质的影响。结果表明,新麦26和师栾02-1具有良好的面包烘焙品质;配麦可有效均衡小麦品质特性,提高烘焙品质。新麦26、师栾02-1和西农979搭配后,3种配麦样品的形成时间、稳定时间均高于单个品种和对照,面包感官评分均显著高于西农979;配麦3的面包感官评分显著高于师栾02-1。由此可见,国内不同品种的优质强筋小麦合理搭配,可有效弥补单个品种的品质缺陷,提升其面包加工性能、适用性和综合效益,满足市场对面包专用粉的需求。     

Simulating the formation of bread crust in a DMTA rheometer

Water evaporates very fast from the surface layers of dough, enhanced by high heating rates at the beginning of baking. The rheological properties of the surface layers play an important role during the baking process, especially in local and overall expansion and water loss. The aim of this study was to determine the rheological properties of bread dough in the heat-moisture dynamics of the baking process, especially in surface drying and delayed drying conditions. The DMTA method was used in tensile mode in order to expose the samples to fast dehydration to simulate real bread crust. The degree of starch gelatinization was demonstrated by the disappearance of the “Maltese cross” (polarized light microscopy). Temperature and water content were monitored during baking. The modulus evolution depended on both the heat and moisture evolution (i.e. immediate or delayed in the present study). In contrast to reports in the literature, starch gelatinization was observed even under drying conditions. Nevertheless, comparison between samples under drying and under delayed drying conditions suggested that water content prevailed in the rheological changes.     

Microstructure, fundamental rheology and baking characteristics of batters and breads from different gluten-free flours treated with a microbial transglutaminase

Gluten is a fundamental component for the overall quality and structure of breads. The replacement of the gluten network in the development of gluten-free cereal products is a challenging task for the cereal technologist. The functionality of proteins from gluten-free flours could be modified in order to improve their baking characteristics by promoting protein networks. Transglutaminase (TGase) has been successfully used in food systems to promote protein cross-linking. In this study, TGase was investigated for network forming potential on flours from six different gluten-free cereals (brown rice, buckwheat, corn, oat, sorghum and teff) used in breadmaking. TGase was added at 0, 1 or 10 U/g of proteins present in the recipe. The effect of TGase on batters and breads was evaluated by fundamental rheological tests, Texture Profile Analysis and standard baking tests. Three-dimensional elaborations of Confocal Laser Scanning Microscopy (CLSM) images were performed on both batters and breads to evaluate the influence of TGase on microstructure. Fundamental rheological tests showed a significant increase in the pseudoplastic behaviour of buckwheat and brown rice batters when 10 U of TGase were used. The resulting buckwheat and brown rice breads showed improved baking characteristics as well as overall macroscopic appearance. Three-dimensional CLSM image elaborations confirmed the formation of protein complexes by TGase action. On the other side, TGase showed negative effects on corn flour as its application was detrimental for the elastic properties of the batters. Nevertheless, the resulting breads showed significant improvements in terms of increased specific volume and decreased crumb hardness and chewiness. Under the conditions of this study, no effects of TGase could be observed on breads from oat, sorghum or teff. Overall, the results of this study show that TGase can be successfully applied to gluten-free flours to improve their breadmaking potentials by promoting network formation. However, the protein source is a key element determining the impact of the enzyme.     

Effects of Wheat Variety and Processing Conditions in Experimental Bread Baking Studied by Univariate and Multivariate Analyses

The effects of variety, mixing conditions and fermentation time on bread loaf characteristics were studied by univariate and multivariate statistical methods. Nearly all the measured bread loaf characteristics were significantly affected by variety, fermentation time, and mixing conditions. Significant interactions were also found. Multivariate analysis (principal component analysis; PCA), was used to find the main variation among the bread samples and to identify the bread loaf characteristics that contributed to describe this variation. The characteristics loaf volume and weight described a large part of the main variation among the loaves and these characteristics were studied in more detail by response surface methodology. The loaf volume and weight response surfaces for varieties, which by multivariate analysis were found to have common properties, followed similar general patterns. It was shown that the experimental design used provided information about the baking performance of wheat flours over a wide range of experimental conditions and, thus, can be a useful supplement to standardised and optimised baking tests.     

The relationship between rheological characteristics of gluten-free dough and the quality of biologically leavened bread

The rheological characteristics of gluten-free doughs and their effect on the quality of biologically leavened bread were studied in amaranth, chickpea, corn, millet, quinoa and rice flour. The rheological characteristics (resistance to extension R, extensibility E, R/E modulus, extension area, stress at the moment of dough rupture) were obtained by uniaxial dough deformation. Specific loaf volume of laboratory prepared gluten-free breads was in significant positive correlation with dough resistance (r = 0.86), dough extensibility (r = 0.98) and peak stress at the moment of dough rupture (r = 0.96). Even if the correlation between R/E modulus and the characteristics of loaf quality were not significant, the breads with the highest specific loaf volume were prepared from flours with R/E closer to the wheat check sample (18 N?mm-1). The results showed, in general, good baking flours exhibited stronger resistance to extension and greater extensibility, but differences found were not directly related to the results of baking tests.     

Wheat flour non-starch polysaccharides and their effect on dough rheological properties

Wheat (Triticum aestivum L.) flour is able to form dough with unique rheological properties that allow bread making. It is well known that wheat protein content affects dough rheological properties, but there is not enough evidence about the role of other minor flour constituents. One such minor constituent is non-starch flour polysaccharides, which are mainly pentosans formed by a xylopyranosyl linear chain branched with arabinofuranosyl residues. Their spatial distribution and branching pattern can affect their relationship with gluten forming proteins and thus influence their functional properties, the dough rheological properties, and thereby the flour baking quality. In this study the content and structural characteristics of non-starch polysaccharides were investigated, as well as their influence on some dough physicochemical parameters. Five different wheat flours samples milled from Uruguayan wheat varieties with diverse rheological and breadmaking properties were used in this study. Water soluble flour polysaccharides were extracted and the amount of pentosans was determined by the orcinol-HCl method. The pentoses composition was determined before and after acidic hydrolysis of the water soluble polysaccharide fractions by GC. No free pentoses were detected in any of the assayed flour samples, so the pentoses composition found in the hydrolyzed samples was attributed to the non-starch water soluble polysaccharides. Water unextractable non-starch polysaccharides were determined by difference between the total and the soluble non-starch polysaccharides flour content.An improved method for the quantification of water extractable and non-extractable non-starch polysaccharides, using baker's yeast, was developed. Using this method, total and soluble non-starch polysaccharides content could reliably be determined both in whole flour and in pentosans enriched fractions. Free monosaccharide content was in the range from 0.03% to 0.06% (w/w), while the arabinose/xylose (Ara/Xyl) ratios varied from 0.8 to 1.4 in soluble non-starch polysaccharides and from 0.7 to 0.9 in total non-starch polysaccharides. The different Ara/Xyl ratios found for water extractable and unextractable arabinoxylans clearly indicates different substitution degrees in the polymers. Analysis of the dough rheological parameters in relation to the water soluble and non-soluble non-starch polysaccharides and the Ara/Xyl ratios from different wheat varieties was performed. A clear relation between some of these parameters could be inferred, since a direct relationship between total unextractable (AXi) content and resistance of dough to extension (P), as well an inverse relationship between the same parameter and dough extensibility (L) were observed. These results suggest that the flour non-starch polysaccharide content, as well the Ara/Xyl ratios may be used as additional parameters to estimate some of the wheat flours dough properties.     

Hagberg Falling Number and Rheological Properties of Wheat Cultivars in Wet and Dry Preharvest Periods

Abstract

The effects of dry and wet preharvest periods on Hagberg falling number (HFN), a parameter of α-amylase activity, and rheological properties including farinograph dough development time (FDT), farinograph absorption (FA), resistance to extension (RE), loaf volume (LV) and baking score (BS) were examined in 30 hexaploid wheat (Triticum aestivum L.) cultivars originating from 19 countries. The cultivars were grown in the field in 2000 – 2010 and HFN and rheological properties were analyzed for three replicates. The cultivars were divided into three groups according to HFN in the wet preharvest period: HFN below 150 s (group H-1), HFN from 250 to 350 s (group H-2), and HFN over 400 s (group H-3). The cultivars in group H-3 were superior to those in either group H-1 or H-2 in all rheological properties except RE. In the dry preharvest periods, HFN was not correlated with rheological properties, while in the wet preharvest period HFN showed a highly significant positive correlation with FDT and BS. The canonical variate analysis for assessment of the general performance of all cultivars with HFN as the main factor and the other rheological properties as subfactors, indicated that the cultivars Stepnaja 30, Garazinko, Kirac, Klein Forten and ?itarka showed the highest potential regardless of preharvest rainfall amounts. In conclusion, differential genetic expression of resistance to preharvest sprouting, maintenance of low α amylase level, high HFN values, maintenance of rheological properties, and baking performance can be reliably detected and measured under wet preharvest conditions.     

Supplementing white maize masa with anthocyanins: Effects on masa rheology and on the in vitro digestibility and hardness of tortillas

The aim of this work was to supplement masa made from nixtamalized white maize flour (NWMF) with anthocyanins (0.0, 0.03, 0.06 and 0.12 g/100 g of masa), and to evaluate the effects on the rheological properties of the masa and on color, staling, in vitro digestibility, and hardness of tortillas. Tortilla baking reduced the content of anthocyanins by about 10%. The color parameters of the tortillas added with anthocyanins was similar to that of tortillas made with blue maize. Attenuated total reflection ATR-FTIR spectra showed that the 1022/1047 peak ratio increased, indicative that retrogradation increased with storage time, but the ratio was significantly lower for tortillas with added anthocyanins than without them, and lower for higher anthocyanins concentration. Freshly made tortillas added with anthocyanins exhibited lower ready digestible (about 35%) and slowly digestible (about 20%), but higher resistant (about 45%) starch fractions. Tortillas with 0.12 g of anthocyanins showed significantly lower hardness than the control tortillas (without added anthocyanins). Both previous mentioned effects can be associated with retrogradation, which on turn could be linked to anthocyanins-starch complexes and inhibition of amylolytic enzymes.     

Flour constituent interactions and their influence on dough rheology and quality of semi-sweet biscuits: A mixture design approach with reconstituted blends of gluten, water-solubles and starch fractions

The aim of this study was to identify the biochemical parameters that alter the soft wheat flour functionality for biscuit-making quality. A 9-point simplex centroid was used to investigate the effect of varying the ratios of gluten, water-solubles and starch-fractions isolated from three different flour grades (patent, middle-cut and clear flours) which exhibited a wide range of compositional and functionality characteristics on the dough rheological behaviour and the semi-sweet biscuit quality parameters. The amounts of soluble and insoluble proteins and pentosans as well as the endogenous lipids in each flour fraction were quantified. Dough consistency, elongational viscosity, hardness, half-relaxation time, relaxation rate constant, cohesiveness and springiness as well as biscuit density, firmness, tearing force and spatial frequency for the different flour fraction combinations were also assessed. Regression models have been developed to predict the responses of the rheological attributes of the dough as well as the biscuit quality characteristics to the compositional changes of the flour blends; in addition to the main linear terms (concentration of starch, gluten and water-solubles isolated from the different flour grades), significant interaction terms were identified which cannot be neglected in any prediction scheme for the dough and biscuit properties. Contour plots were drawn in an effort to better understand the overall property responses of the dough and biscuits. Significant relationships among certain dough rheological parameters and biscuit characteristics were found, implying a functional role for the total, soluble and insoluble proteins, pentosans and lipids in biscuit making.     

Strain Hardening Properties and Extensibility of Flour and Gluten Doughs in Relation to Breadmaking Performance

The mechanical properties of flour–water doughs and hydrated gluten of different wheat cultivars were determined. Measurements were performed at small deformations (dynamic measurements) as well as at large deformations (biaxial extension measurements). Results of dynamic measurements of flour doughs related poorly to breadmaking quality. For hydrated gluten doughs, all having the same water content, it was found that glutens from wheat cultivars with good baking quality had higher values for the storage modulus,G, and lower values for the loss tangent. The relevant type of deformation around an expanding gas bubble is biaxial extension. Wheats with a good baking performance exhibited greater strain hardening and greater extensibility. The differences in strain hardening observed at 20 °C were also present at 55 °C. No clear effects of NaCl or emulsifiers on the biaxial extension properties of flour dough were found. Extensograms as well as Alveograms from the flour doughs showed that, in general, good baking flours exhibited stronger resistance to extension and a greater extensibility, but differences found were not directly related to the results of the baking tests. The results indicate that the baking performance of dough is related to a combination of at least three different rheological characteristics.     

白粉病对冬小麦籽粒品质性状及产量的影响

为了解小麦感染白粉病后籽粒品质及产量的变化,选用对白粉病高感的小麦品种偃展4110和中抗品种豫农416为材料,利用人工接种并结合药剂控制发病等级的方法,分析了白粉病对小麦籽粒蛋白组分、面团流变学参数及淀粉糊化特性的影响。结果表明,随白粉病病情指数的增加,小麦籽粒总蛋白质、清蛋白和麦谷蛋白含量降低,而醇溶蛋白和球蛋白含量增加,蛋白组分间不平衡加剧,同时,弱化度降低、稳定时间、粉质质量指数、拉伸曲线面积和降落值提高。病情指数增加导致峰值黏度、低谷黏度、最终黏度和反弹值降低。在产量构成因素中,白粉病对穗粒数的影响相对较小,对千粒重的影响最大,白粉病严重时,千粒重降低5~7g,偃展4110和豫农416的产量损失分别达26.2%和15.8%。     

我国春麦区部分小麦品种品质状况分析

1999年将 38份春小麦品种 (品系 )种植于内蒙古呼和浩特 ,对其磨粉品质和面包烘烤品质进行了评价。结果表明 ,我国春小麦品种的面包烘烤品质较差 ,不同地区品种间品质差异较大 ,辽宁和内蒙品种的磨粉品质和面包烘烤品质优于其它地区的品种。回归分析表明 ,蛋白质含量和单位蛋白质含量的面包体积决定了面包体积总变异的 99.9% ,硬度、沉淀值和吸水率对面包总分有重要作用。品种的出粉率主要取决于 1心槽路出粉率 ,2心和 1皮槽路出粉率对出粉率贡献也较大。高分子量麦谷蛋白亚基 (HMW GS)Glu A1和Glu D1位点的等位变异与品质性状密切相关。面包烘烤品质的改良应在分析HMW GS的基础上 ,将硬度作为选择指标之一 ,适当提高蛋白质含量 ,重点加强对沉淀值的选择