Phytate negatively influences wheat dough and bread characteristics by interfering with cross-linking of glutenin molecules

The influence of added phytate on dough properties and bread baking quality was studied to determine the role of phytate in the impaired functional properties of whole grain wheat flour for baking bread. Phytate addition to refined flour at a 1% level substantially increased mixograph mixing time, generally increased mixograph water absorption, and reduced the SDS-unextractable protein content of dough before and after fermentation as well as the loaf volume of bread. The added phytate also shifted unextractable glutenins toward a lower molecular weight form and increased the iron-chelating activity of dough. It appears that phytate negatively affects gluten development and loaf volume by chelating iron and/or binding glutenins, and consequently interfering with the oxidative cross-linking of glutenin molecules during dough mixing. Phytate could be at least partially responsible for the weak gluten network and decreased loaf volume of whole wheat flour bread as compared to refined flour bread.     

Can bread wheat quality be determined by gluten index?

In recent years, the Israeli wheat industry has suffered from quality problems that endangered the possibility of growing bread wheat in Israel. In addition to relying upon grain protein and test weight, the Israeli wheat market has therefore begun using the gluten index (GI) test method. To shed new light on wheat grain quality determinations, wheat grain samples were analyzed for GI and other quality parameters such as dry and wet gluten, SDS-sedimentation, and loaf volume. In many cases, low-GI grains exhibited good dough and bread quality. This could be attributed to the difference in GI values of the wheat versus the corresponding flour. Hence, milling plays a major role in GI determination. Furthermore, grain and white flour GI values did not correlate with other accepted quality parameters, such as SDS-sedimentation and loaf volume. Therefore, it is suggested that the GI be used with caution, and that the addition of other methods can improve wheat quality determination.     

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.     

施氮量对强筋小麦产量、氮素利用率和品质的影响

为探明协同提高强筋小麦产量、氮素利用率和品质的施氮量,以强筋小麦品种济麦20（中穗型）和洲元9369（大穗型）为材料, 研究了180、240和300 kg·hm^-2三个氮肥水平（分别用N180、N240和N300表示）对强筋小麦产量、氮素利用率、品质及其相关指标的影响。结果表明,相同施氮量下,洲元9369的产量、氮素利用率、面团形成时间、面团稳定时间、面包体积和面包评分均高于济麦20。当施氮量由N180增至N240时,2个品种的产量无显著变化,但沉降值、面团形成时间、面团稳定时间、面包体积和面包评分均显著提高;施氮量增至N300后,2个品种的产量和品质又都显著下降,籽粒总蛋白含量、谷蛋白含量、SDS-不可溶性谷蛋白含量、醇溶蛋白含量和谷蛋白聚合指数均明显降低,而SDS-可溶性谷蛋白含量和谷醇比却表现为上升趋势。经相关分析,SDS-不可溶性谷蛋白含量、谷蛋白聚合指数与面团形成时间、面团稳定时间、面包体积和面包评分均呈显著正相关。以上结果表明,谷蛋白聚合程度降低是过量施氮条件下强筋小麦品质下降的主要原因。综合考虑小麦产量、氮素利用率和籽粒品质,240 kg·hm^-2为本研究条件下的最佳施氮量。     

Interrelationships of Protein Composition, Protein Level, Baking Process and the Characteristics of Hearth Bread and Pan Bread

Baking performance of hearth bread and pan bread were investigated using 10 wheat varieties with variable protein quality. For most varieties, samples were selected at two protein levels, approximately 11 and 13% (d.m.). The effects of flour quality on loaf characteristics were different for hearth bread compared to pan bread, where both protein quality and protein content affect loaf volume positively in an optimised baking test. Hearth bread is more complex as both the form ratio and loaf volume are critical external characteristics. When using fixed proving time, the form ratio was positively affected by dough resistance and mixing peak time at high speed mixing, and negatively affected by dough extensibility. Dough resistance and mixing peak time correlated strongly to the HMW glutenin composition, whereas dough extensibility was related to protein content. In contrast to the form ratio, loaf volume was positively affected by dough extensibility, whereas protein quality had no significant effect. This was seen both for doughs produced at optimal mixing time at high speed mixing (126 rev/min) and for doughs produced at fixed mixing times at low speed mixing (63 rev/min). When proving time was optimised to achieve a defined form ratio, flours of strong protein quality should be proved longer than flours of week protein quality, resulting in higher loaf volume for flours of the strongest protein quality. With respect to protein content, the positive effect of protein content on loaf volume was counteracted due to reduced proving time when aiming for a defined form ratio.     

Effect of sodium chloride on gluten network formation,dough microstructure and rheology in relation to breadmaking

Sodium chloride (NaCl) is an essential ingredient to control the functional properties of wheat dough and bread quality. This study investigated the effect of NaCl at 0, 1 and 2%, (w/w, flour base) on the gluten network formation during dough development, the dough rheology, and the baking characteristics of two commercial flours containing different levels of protein (9.0 and 13.5%) and with different glutenin-to-gliadin ratios. Examination of the dough structure by confocal microscopy at different stages of mixing show that the gluten network formation was delayed and the formation of elongated fibril protein structure at the end of dough development when NaCl was used. The fibril structure of protein influenced the dough strength, as determined by strain hardening coefficient and hardening index obtained from the large deformation extension measurements. NaCl had a greater effect on enhancing the strength of dough prepared from the low protein flour compared to those from the high protein flour. The effect of NaCl on loaf volume and crumb structure of bread followed a similar trend. These results indicate that the effect of NaCl on dough strength and bread quality may be partially compensated by choosing flour with an appropriate amount and quality of gluten protein.     

Effect of physicochemical and empirical rheological wheat flour properties on quality parameters of bread made from pre-fermented frozen dough

The objective of this study was to examine the influence of flour quality on the properties of bread made from pre-fermented frozen dough. The physicochemical parameters of 8 different wheat flours were determined, especially the protein quality was analysed in detail by a RP-HPLC procedure. A standardized baking experiment was performed with frozen storage periods from 1 to 168 days. Baked bread was characterised for specific loaf volume, crumb firmness and crumb elasticity. The results were compared to none frozen control breads. Duration of frozen storage significantly affected specific loaf volume and crumb firmness. The reduction of specific loaf volume was different among the used flours and its behaviour and intensity was highly influenced by flour properties. For control breads wet gluten, flourgraph E7 maximum resistance and RVA peak viscosity were positively correlated with specific loaf volume. However, after 1–28 days of frozen storage, wet gluten content was not significantly influencing specific loaf volume, while other parameters were still significantly correlated with the final bread properties. After 168 days of frozen storage all breads showed low volume and high crumb firmness, thus no significant correlations between flour properties and bread quality were found. Findings suggest that flours with strong gluten networks, which show high resistance to extension, are most suitable for frozen dough production. Furthermore, starch pasting characteristics were also affecting bread quality in pre-fermented frozen dough.     

不同小麦粉混配品质性状的变化

为了研究小麦粉混配过程中品质性状的变化，分析了陕西省13个推广小麦品种及其23种混配粉的蛋白质品质和面团流变学特性。结果表明，强筋小麦不同批次制粉品质变化较大，中筋和弱筋小麦品质变化相对较小，不同方式配粉面团流变学特性变化规律不同。强筋 中筋和强筋 弱筋两种方式配粉稳定时间测定值比理论值减少，延伸性有增有减。同时，强筋 中筋=强筋的配粉延伸性以减小为主，而强筋 中筋=中筋的配粉延伸性增加，2个中筋粉或中筋与弱筋粉混配延伸性明显增加。混配粉面筋含量、沉淀值、稳定时间和延伸性测定值与由基础品种估算的理论值无显著差异，而且呈极显著正相关，相关系数分别为0．9818^**、0．9776^**、0．8594^**和0．7189^**。文中还提出了根据配粉需要估算基础品种混配比例的方法。     

Wheat Bread Quality as Influenced by the Substitution of Waxy and Regular Barley Flours in Their Native and Extruded Forms

The substitution of wheat flour with barley flour (i.e. native or pretreated/extruded) reduced the loaf volume. Depending on the barley variety and flour pretreatments, the colour and firmness/texture of the bread loaves were altered. Amongst the barley breads prepared from native flours (at 15% barley flour substitution level), Phoenix had higher loaf volume and lower crumb firmness than Candle. However, amongst the barley breads prepared from extruded flours, CDC-Candle had higher loaf volume and lower crumb firmness than Phoenix. The lower loaf volume and firmer crumb texture of barley breads as compared with wheat bread may be attributed to gluten dilution. Also, the physicochemical properties of barley flour components, especially that of β-glucan, can affect bread volume and texture. β-glucan in barley flour, when added to wheat flour during bread making, could tightly bind to appreciable amounts of water in the dough, suppressing the availability of water for the development of the gluten network. An underdeveloped gluten network can lead to reduced loaf volume and increased bread firmness. Furthermore, in yeast leavened bread systems, in addition to CO₂, steam is an important leavening agent. Due to its high affinity for water, β-glucan could suppress the amount of steam generated, resulting in reduced loaf volume and greater firmness. In the present study, breads made with 15% HTHM CDC-Candle flour had highly acceptable properties (loaf volume, firmness and colour) and it indicated that the use of extruded barley flours would be an effective way to increase the dietary fibre content of barley breads.     

Large deformation stress relaxation and compression-recovery of gluten representing different wheat classes

Despite the great variety of physicochemical and rheological tests available for measuring wheat flour, dough and gluten quality, the US wheat marketing system still relies primarily on wheat kernel hardness and growing season to categorize cultivars. To better understand and differentiate wheat cultivars of the same class, the tensile strength, and stress relaxation behavior of gluten from 15 wheat cultivars was measured and compared to other available physicochemical parameters, including but not limited to protein content, glutenin macropolymer content (GMP) and bread loaf volume. In addition, a novel gluten compression–relaxation (Gluten CORE) instrument was used to measure the degree of elastic recovery of gluten for 15 common US wheat cultivars. Gluten strength ranged from 0.04 to 0.43 N at 500% extension, while the degree of recovery ranged from 5 to 78%. Measuring gluten strength clearly differentiated cultivars within a wheat class; nonetheless it was not a good predictor of baking quality on its own in terms of bread volume. Gluten strength was highly correlated with mixograph mixing times (r = 0.879) and degree of recovery (r = 0.855), suggesting that dough development time was influenced by gluten strength and that the CORE instrument was a suitable alternative to tensile testing, since it is less time intensive and less laborious to use.     

Development of an Aegilops longissima substitution line with improved bread-making quality

This study focuses on the effect of Aegilops longissima on wheat bread making quality. Chromosome 1S^l disomic addition line of Ae. longissima (DAL1S^l) had significantly higher dough strength, grain hardness, mixographic peak height, band width, and unextractable polymeric protein content compared with wheat. DAL1S^l also had additional glutenin and gliadin proteins contributed by Ae. longissima. The larger size of 1S^l coded HMW-GSs sequenced from DAL1S^l and their phylogenetic similarity to the D-genome-coded subunits were suspected to be one of the major reasons for the increased dough strength of DAL1S^l. To transfer the chromosome 1S^l genes responsible for the good bread-making quality to wheat, we generated a chromosome-specific disomic substitution line [DSL1S^l(1A)] by crossing DAL1S^l with nulli 1A tetra 1B genetic stock and further selection. Grain quality analysis revealed significantly lower grain hardness and significantly higher dough strength, farinograph development time, stability time, gluten index, bread loaf volume, and bread quality score in DSL1S^l(1A), compared with wheat. However, the increased bread loaf volume and quality were not proportional to the relatively higher increases in dough strength and gluten index, indicating importance of other traits influencing bread making quality. The presence of a minor hardness locus on chromosome 1A is speculated.     

Functional Properties of Wheat Gliadins. I. Effects on Mixing Characteristics and Bread Making Quality

The effects of addition of total gliadin and gliadin subfractions on the 2 g Mixograph parameters and loaf volume data of cv. Hereward base flour were studied. The addition of increasing levels of total gliadin and gliadin subgroups to cv. Hereward base flour decreased the overall dough strength, as evidenced by decreases in the values for mixing time (MT), mixing stability (MS) and work input (WI). The decreasing order of these parameters for different gliadins was: ω1- >, γ-, > β-, > α-gliadins. The mixing tolerance, as measured by resistance breakdown (RBD) and bandwidth breakdown (BWBD), decreased as a result of addition of different fractions. However, Peak dough resistance (PDR) values increased with addition of individual groups of gliadins and gluten to the base flour. A linear relationship was found between the PDR and loaf volume when individual groups of gliadin were added to the base flour. The ω-gliadins produced the least positive effects on PDR. Addition of total gliadin and its subgroups substantially improved loaf volumes of pan breads. The ω-gliadins again resulted in a smaller increase in loaf volume.     

Impact of lipases with different substrate specificity in wheat flour separation on the properties of the resultant gluten

Wheat gluten was isolated in a laboratory dough-batter flour separation process in the presence or absence of lipases differing in hydrolysis specificity. The obtained gluten was blended with wheat starch to obtain gluten-starch (GS) blends of which the water and oil binding capacities were investigated. Furthermore, GS blends were mixed into dough and processed into model breads, of which dough extensibility and loaf volume were measured, respectively. In comparison to GS blends prepared with control gluten, oil binding capacity was higher when GS blends contained gluten isolated with Lecitase Ultra (at 5.0 mg enzyme protein/kg flour), a lipase hydrolyzing both non-polar and polar lipids. Additionally, dough extensibility and total work needed for fracture were lower for dough prepared from GS blends containing gluten isolated with Lipolase (at 5.0 mg enzyme protein/kg flour), a lipase selectively degrading non-polar lipids. In GS blend bread making, this resulted in inferior loaf volumes. Comparable GS blend properties were measured when using control gluten and gluten isolated with YieldMAX, a lipase mainly degrading N-acyl phosphatidylethanolamine. In conclusion, properties of GS blend model systems are altered when gluten prepared in the presence of lipases is used to a degree which depends on lipase specificity and concentration.     

A new lean no time test baking method with improved discriminating power

In response to customer concerns related to gluten strength in commercial baking, the Canadian Grain Commission assessed whether the Canadian Short Process (CSP) test bake method was generating useful data related to intrinsic strength of wheat varieties. Assessment of CSP loaf volume data for Canadian variety trials spanning 2003 to 2013 showed very little correlation with dough strength parameters as measured by farinograph and extensigraph. A lean no time (LNT) test baking method was developed that can better discriminate genotypes and provide objective indicators of the effect of intrinsic dough strength on baking quality. From early method development, through method validation and verification using diverse sets of samples targeting different Canadian wheat classes and grown in three different crop years, results showed the LNT method to be more discriminating and easily adopted by other laboratories. In 2015, the LNT method was adopted as the method of choice in future Canadian variety registration trials. The LNT method is fast, simple and well-suited to high throughput test baking conditions encountered in the evaluation of large numbers of breeder lines. A new objective parameter, loaf top ratio, was also introduced and found to correlate well with dough strength and dough handling properties.     

A new lean no time test baking method with improved discriminating power

In response to customer concerns related to gluten strength in commercial baking, the Canadian Grain Commission assessed whether the Canadian Short Process (CSP) test bake method was generating useful data related to intrinsic strength of wheat varieties. Assessment of CSP loaf volume data for Canadian variety trials spanning 2003 to 2013 showed very little correlation with dough strength parameters as measured by farinograph and extensigraph. A lean no time (LNT) test baking method was developed that can better discriminate genotypes and provide objective indicators of the effect of intrinsic dough strength on baking quality. From early method development, through method validation and verification using diverse sets of samples targeting different Canadian wheat classes and grown in three different crop years, results showed the LNT method to be more discriminating and easily adopted by other laboratories. In 2015, the LNT method was adopted as the method of choice in future Canadian variety registration trials. The LNT method is fast, simple and well-suited to high throughput test baking conditions encountered in the evaluation of large numbers of breeder lines. A new objective parameter, loaf top ratio, was also introduced and found to correlate well with dough strength and dough handling properties.     

Redox Reactions in Wheat Dough as Affected by Ascorbic Acid

Ascorbic acid (AA) is used as bread improver, as its addition to dough causes an increase in loaf volume and an improvement in crumb structure. To explain these effects we review the stereospecificity of the improver action and the properties of ascorbate oxidase and glutathione dehydrogenase and the occurrence of low molecular thiols in flour and their concentration changes during dough mixing in the presence and absence of AA. On the basis of the results the improver action of AA is explained by a reaction sequence leading to a rapid removal of endogenous GSH, which otherwise would cause dough weakening by sulphhydryl/disulphide interchange reactions with gluten proteins. To test this hypothesis the binding sites of endogenous GSH in gluten proteins have been determined by the addition of³⁵S-labelled GSH as a tracer to flour before dough mixing. The distribution of radioactivity in the gliadin and glutenin fractions of gluten obtained from dough indicates that the major portion of GSH is bound to glutenins. The isolation and sequence analysis of radioactive cystine peptides from an enzymatic digest of glutenins demonstrates that GSH is almost exclusively linked to those cysteine residues of LMW subunits that have been proposed to form intermolecular disulphide bonds.     

Effects of vacuum mixing and mixing time on the processing quality of noodle dough with high oat flour content

The effects of different mixing parameters (vacuum mixing and mixing time) on oat (70% oat flour) and wheat noodle dough were investigated on the basis of textural properties and gluten formation. The results showed that at a vacuum degree of −0.06 MPa and mixing time of 10 min, oat and wheat dough sheets exhibited the highest resistance to extension and glutenin macropolymer (GMP) content, and had the most compact and uniform gluten network. Compared with wheat noodle dough, oat dough had lower resistance to extension, lower tightly bound water content, and higher GMP content. Microstructural examination showed that oat noodle dough had a more aggregated distribution of gluten protein compared with wheat noodle dough under the optimum mixing parameters. Furthermore, the poor binding ability of vital wheat gluten with water molecules caused the indexes of oat noodle dough to be more strongly affected by the changes in mixing parameters than wheat noodle dough.     

基于RIL群体的小麦籽粒性状与品质特性关系分析

为了探究预测小麦品质的方法,利用以小麦品种川农17与绵阳11为亲本构建的重组自交系群体为研究材料(共169个家系),分析了其籽粒性状和品质特性及二者之间的关系。结果表明,小麦粒长与降落值、面团形成时间和面团稳定时间呈极显著负相关,粒宽与沉降值、湿面筋含量和面筋指数呈极显著负相关,千粒重与降落值、沉降值、面团形成时间和面团稳定时间呈极显著负相关,容重与降落值、面团形成时间和面团稳定时间呈极显著正相关,与沉降值、湿面筋含量和面筋指数呈极显著负相关。粒长、千粒重和容重决定了降落值总变异的77.9%,粒长和千粒重决定了沉降值总变异的35.0%,容重和千粒重决定了面团形成时间总变异的50.7%,容重和千粒重决定了面团稳定时间总变异的49.3%,粒长、粒宽和容重决定了湿面筋含量总变异的51.0%,容重决定了面筋指数总变异的45.7%。说明在小麦品质育种中,粒长、粒宽、千粒重和容重可作为预测小麦品质优劣的选择指标。     

On the relationship between large-deformation properties of wheat flour dough and baking quality

Baking performance for bread and puff pastry was tested for Six European and two Canadian wheat cultivars and related to the rheological and fracture properties in uniaxial extension of optimally mixed flour–water doughs and doughs to which a mix of bakery additives was added. Extensive baking tests were performed as a function of water addition for puff pastry and as a function of water addition and mixing time for bread. For optimum baking performance, puff pastry doughs required lower water additions than bread doughs. Baking performance of the flours differed for the two products. For puff pastry, higher volumes were obtained per gram of flour than for bread. Puff pastry volume was positively correlated with optimum bread dough mixing time, while bread volume was not. Instead, bread volume was positively correlated with gluten protein content.All doughs exhibited strain hardening, a more than proportional increase of the stress with the strain. For all doughs fracture, stress and strain increased with increasing displacement speed of the hook and decreasing temperature. Large differences were observed between the cultivars regarding stress, strain hardening, strain rate-dependency of the stress, fracture stress and fracture strain. At both 25 and 45 °C, addition of a mix of bakery additives resulted in a decrease of the stress at relatively small strains and a significant increase of the strain hardening coefficient. Fracture strains remained the same or increased as a result of addition of the mix. Differences between flours regarding the strain rate and temperature-dependency of the fracture strain remained. The weaker the dough, the stronger the strain rate and temperature-dependency of the fracture strain.Puff pastry volume was positively correlated with strain hardening and negatively with the strain rate-dependency of the stress. In short, the stronger the dough, the higher the puff pastry volume. For bread, it were not the strongest doughs that gave the highest loaf volumes, but those with intermediate dough strength. Low volumes for puff pastry and bread were found for doughs having a low fracture stress and low strain hardening coefficients. Loaf volumes of flours with high dough strength (i.e. high stress-level and high strain hardening) gave intermediate loaf volumes. We concluded that a high stress can hamper the extensibility of dough films between gas cells, thus limiting the expansion of gas cells during fermentation and baking and hence the loaf volume that can be obtained.     

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.