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.     

Bread-making performances of durum wheat semolina,as affected by ageing

The present study addresses the influence of ageing on the bread-making performances of durum wheat semolina by bread image analysis. Bread loaves were produced from semolina samples stored in 4 different packaging materials for up to 150 days. Sampling and bread-making trials were performed every 15 days. Results showed that ageing does affect durum wheat semolina bread-making performances, highlighting that storage time, rather than the type of packaging material, is the main factor determining quality changes in the final bread samples. In particular, a change in the crust colour parameters and a reduction of the bread slice area and height by 20–35% were observed with increasing semolina storage time, along with a slight increase of crust % area. The change in farinographic parameters of dough suggests that the observed reduction of technological quality might be due to increased stiffness and reduced extensibility of gluten occurring in aged semolina. Unlike common wheat flours, which usually improve their technological features during ageing, durum wheat semolina is negatively affected in its quality by storage. The study highlights the importance of considering bread-making performances among the quality parameters to be taken into account for the shelf life evaluation of durum wheat semolina.     

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.     

Impact of Starch Properties on Hearth Bread Characteristics. II. Purified A- and B-granule Fractions

Using the nine different wheat varieties, sixteen different flours were blended to achieve two protein levels 11 and 13%. Mixing characteristics of the flours were analysed by Farinograph and Mixograph. Thermal properties of flour were measured by differential scanning calorimetry (DSC). Starch gelatinisation, pasting viscosity, and gelation properties were assessed by a Rapid Visco-Analyser (RVA). Hearth bread loaves were produced from the flours using a small-scale baking method. The results from the analyses of flour were related to the properties of hearth bread loaves by multivariate statistical methods. The Partial Least Squares Regression (PLS) model (Model 1) obtained using results from grain and flour analysis (no starch analysis included) as X – matrix explained 70% of the total variance in hearth bread characteristic form ratio. If flour-pasting properties were included in the PLS1 model (Model 2) the explained variance increased to 77%. The model obtained including the DSC parameters of wheat flour explained 76% of the total variance in form ratio (Model 3). This emphasises the importance of starch in wheat flour and that it is possible to find wheat flour starch quality parameters in addition to protein quality that is important for hearth bread quality. No good models were obtained for hearth bread characteristics loaf volume and weight.     

Fractionation of cereal flour by sedimentation in non-aqueous systems. II. Rheological characterisation and baking performance of the protein fraction

A previously described method for the non-aqueous fractionation of cereal flours by sedimentation in non-aqueous solvents was carried out using flours of three wheat cultivars differing in baking performance, as well as one rye and one barley flour. The method was based on differences in the densities of starch (higher) and protein (lower). Thus, suspending finely milled flour in an inert solvent mixture with a density in between the densities of starch and protein yielded a sedimented starch fraction and a protein-rich fraction at the surface of the solvent. Further purification of this upper fraction provided a protein fraction, a middle fraction, and a lipid fraction. The protein fractions were examined by means of rheological methods such as micro-extension tests and creep-recovery tests. They also were reconstituted to standard flour with a protein content of 13.5%, which was used for micro-scale baking tests. Compared to aqueous isolated gluten, the hydrated protein fractions from wheat were much more extensible and had a lower resistance to extension. The baking performance of the wheat protein fractions was superior to gluten and comparable to the native wheat flours. The protein fraction from rye gave a wheat-like bread crumb, whereas the barley protein was not suited for bread making.     

New strategies for a reliable assessment of baking quality of wheat – Rethinking the current indicator protein content

New strategies for a reliable assessment of baking quality of wheat are required since the protein content is a widely discussed indicator in this respect. In this study, the indicator value of the protein content for baking quality was evaluated using almost 600 wheat samples representing different quality and varieties. NIRS calibrations were developed to estimate bread volume at different levels of processing. Bread volume increased with increasing protein content in a wide curvilinear relationship with an R² of 0.59. At protein contents above 12% representing the relevant range for trading, the R² dropped to 0.15. Different wheat varieties showed differential responses (i.e. linear and non-linear) in bread volume to increasing protein content. The performance of NIRS calibrations for bread volume were best at the processing level of dough (R² 0.81) and good at the level of whole grains (R² 0.70). Hence, the protein content is not a reliable indicator for baking quality on its own. Bread volume was predicted better by NIRS calibrations than by protein content. A strategy is presented paying attention to the variety specific interplay between baking quality and protein content with implications for the variety registration system, trading, breeding and nitrogen fertilisation.     

Extensional Flow Studies of Wheat Flour Dough. I. Experimental Method for Measurements in Contraction Flow Geometry and Application to Flours Varying in Breadmaking Performance

An experimental method is reported for extensional measurements on wheat flour doughs in contraction flow geometry. In this method the transient stress under constant extension rate was measured, followed by stress relaxation measurement after cessation of flow. Four different wheat cultivars (with large differences in bread volume) were used to evaluate the usefulness of the method and to find how different parameters relevant to baking quality could be extracted from the data. The plot of transient viscosity against time showed the effect known as strain hardening, appearing at a Hencky strain roughly independent of the strain rate but differing between the wheat varieties. The relaxation rate curves for the four wheat varieties were similar except at the highest strain rate, 7·40 s⁻¹. It was decided in the following case study to use the highest strain rate, 7·40 s⁻¹and to extract three parameters from the stress growth plot and three parameters from the stress relaxation rate plot. In the case study, flours of 17 wheat varieties were mixed in the Mixograph to maximum resistance before being subjected to the contraction flow measurement. The six parameters extracted from each wheat flour dough measurement, together with the corresponding protein content, Zeleny value, and bread volume, were evaluated by multivariate analysis. A model for predicting the bread volume from the contraction flow parameters explained 94·6% of the variation in bread volume, while a model with Zeleny values and protein contents included explained 97·2%.     

面筋蛋白对小麦粉理化性质及面包烘焙品质的影响

为明确不同类型小麦的面粉改良方案,为我国优质面包专用粉的生产提供理论与技术支持,以三个筋力不同的小麦品种宁麦13、扬麦16和郑麦9023为材料,通过洗面筋法提取各供试材料的湿面筋,将其冷冻干燥后按照7%、8%、9%、10%、11%的添加比例与各自面粉进行配比,对配粉的面包烘焙品质、面粉理化性质和面团流变学特性进行了测定分析。结果发现,随着面筋蛋白添加量的提高,配粉的蛋白质、湿面筋、谷蛋白大聚体(GMP)含量和沉降值逐步上升;粘度参数和面团弱化度有所下降;糊化温度和糊化时间呈上升趋势。在同一添加量下,强筋小麦的烘焙品质和面粉理化性质始终优于中筋小麦和弱筋小麦。随着面筋蛋白添加量的提高,面包体积、弹性、回复性、内聚力增大,而硬度、咀嚼性减小,感官品质得到改善。面筋蛋白添加量超过一定范围(宁麦13、扬麦16添加9%,郑麦9023添加8%),面包品质改良效果变缓,且色泽不断加深。综上所述,适量添加面筋蛋白可改变面粉的理化性质,提高其面包烘焙品质;配粉的蛋白质含量为18%左右是最经济的面包烘焙品质改良方案。     

Evaluation of the rheological properties of dough and quality of bread made with the flour obtained from old cultivars and modern breeding lines of spelt (Triticum aestivum ssp. spelta)

This work evaluates rheological properties of dough and quality of bread prepared from the flour of ancient varieties and modern breeding lines of spelt compared to common wheat. Spelt flours of old varieties exhibited similar water absorption; the largest was noted in the STH-8 line flour. Spelt doughs had longer development time and were more stable than wheat dough. The doughs made of old spelt varieties were more resistant to extension than that produced from new lines flours. Of the spelt breads, this of the STH-8 line spelt line had the largest loaf volume but smaller than wheat bread. In addition, spelt doughs had similar porosity; the most porous was the bread baked from the Frankenkorn cv, Schwabenkorn cv and STH-8 line flours. Moreover, the crumb of the bread manufactured from the flours of spelt variety Frankenkorn and the STH 28-4614 line showed the greatest resistance to compression and the smallest compressibility.     

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     

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.     

Effect of the grain protein content locus Gpc-B1 on bread and pasta quality

Grain protein concentration (GPC) affects wheat nutritional value and several critical parameters for bread and pasta quality. A gene designated Gpc-B1, which is not functional in common and durum wheat cultivars, was recently identified in Triticum turgidum ssp. dicoccoides. The functional allele of Gpc-B1 improves nitrogen remobilization from the straw increasing GPC, but also shortens the grain filling period resulting in reduced grain weight in some genetic backgrounds. We developed isogenic lines for the Gpc-B1 introgression in six hexaploid and two tetraploid wheat genotypes to evaluate its effects on bread-making and pasta quality. In common wheat, the functional Gpc-B1 introgression was associated with significantly higher GPC, water absorption, mixing time and loaf volume, whereas in durum wheat, the introgression resulted in significant increases in GPC, wet gluten, mixing time, and spaghetti firmness, as well as a decrease in cooking loss. On the negative side, the functional Gpc-B1 introgression was associated in some varieties with a significant reduction in grain weight, test weight, and flour yield and significant increases in ash concentration. Significant gene × environment and gene × genotype interactions for most traits stress the need for evaluating the effect of this introgression in particular genotypes and environments.     

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。     

Storage changes in the quality of sound and sprouted flour

Sound and sprouted flours (24 and 48 hr) from bread wheat (WL-1562), durum wheat (PBW-34) and triticale (TL-1210) were stored at room temperature (34.8°C) and relative humidity (66.7%) for 0, 45, 90 and 135 days to assess the changes in physico-chemical and baking properties. Protein, gluten, sedimentation value, starch and crude fat decreased during storage in all the samples; however, the decrease was more in sprouted flours. Free amino acids, proteolytic activity, diastatic activity and damaged starch decreased with increase in storage period. Total sugars and free fatty acids increased more rapidly in the flours of sprouted wheats during 135 days of storage. Loaf volume of breads decreased during storage in both sound and sprouted flour but the mean percent decrease in loaf volume was more in stored sound flours. Aging of sprouted flour for 45 days improved the cookie and cake making properties but further storage was of no value for these baked products.Chapati making properties of stored sound and sprouted flour were inferior to that of fresh counterparts.     

黄淮冬麦区强筋小麦品种的产量及品质分析

为了解当前黄淮冬麦区强筋小麦品种的产量和品质表现,选用9个近年来黄淮麦区育成、在河南省大面积推广种植的强筋小麦品种,种植于河南的郑州和泛区,按AACC或国标的方法对其蛋白质和淀粉品质进行分析。结果表明,供试强筋小麦品种的产量显著低于高产对照品种周麦18;有5个品种的有效穗数显著高于周麦18,有3个品种与周麦18差异不显著;分别有1个品种的穗粒数、千粒重与周麦18差异不显著,其余品种均显著低于周麦18。说明黄淮冬麦区强筋小麦品种的穗粒数和千粒重有待提高。分析各品种的品质指标,对于湿面筋含量,有5个品种在两个试点均达国标,有2个品种在一个试点达国标;弱化度、面包体积、面包评分等反映面筋质量的品质指标均表现为郑州点优于泛区点;弱化度、面包体积在2个试点的差异达极显著水平;面包评分在2个试点的差异达显著水平。含5+10亚基的品种中,非1BL/1RS易位品种的烘焙品质显著优于1BL/1RS易位品种。郑麦366、师栾02-1、新麦26的麦谷蛋白亚基构成和面包烘焙品质均较优。郑麦366、矮抗58的峰值黏度较高,淀粉糊化特性较好,适合制作优质面条。     

Volume, texture, and molecular mechanism behind the collapse of bread made with different levels of hard waxy wheat flours

Physico-chemical properties of bread baked by partially replacing normal wheat (Triticum aestivum L.) flour (15, 30, and 45%) with two hard waxy wheat flours were investigated. Substitution with waxy wheat flour resulted in higher loaf volume and softer loaves. However, substitution at >30% resulted in excessive post-bake shrinkage and a ‘key-hole’ shape with an open crumb structure. Bread crumb microstructure indicated a loss of starch granule rigidity and fusing of starch granules. The cells in the interior of the bread did not become gas-continuous and as a result, shrunk as the loaf cooled. Soluble starch content was significantly higher in bread crumb containing waxy wheat flour than in control bread. Debranching studies indicated that the soluble starch in bread made with 30-45% hard waxy wheat flour was mostly amylopectin. Incorporation of waxy wheat flour resulted in softer bread immediately after baking but did not retard staling upon storage.     

The Role of Gluten Proteins in the Baking of Arabic Bread

Fractionation and reconstitution/fortification techniques were utilised to study the role of gluten in Arabic bread. Glutens from two wheat cultivars of contrasting breadmaking quality were fractionated by dilute HCl into gliadin and glutenin. Gluten, gliadin and glutenin doughs from the good quality flour had higher G ′ and lower tan δ values than those from the poor quality flour at all the frequencies examined. Interchanging the gliadin and glutenin fractions between the reconstituted flours showed that the glutenin fraction is largely responsible for differences in the breadmaking performance. Fortification of an average quality flour with the gliadin and glutenin fractions from the poor and good quality flours, at the levels of 1% and 2% (protein to flour mass), induced marked differences in the mechanical properties of bread. The resilience of the loaves was not adversely affected by the addition of gliadins and increased, with a concomitant significant (p<0·05) improvement in quality, at the 2% level of fortification with gliadins from the good quality flour. Addition of glutenin resulted in loaves with leather-like properties that became particularly apparent at the higher level of fortification; the observed deterioration in quality paralleled the increase in the elastic character of the doughs. It is suggested that highly-elastic doughs are not compatible with the rapid expansion of gases at the high-temperature short-time conditions employed in the baking of Arabic bread and that there exists a threshold in dough elasticity beyond which a rapid decline in quality takes place.     

Baking quality of emmer-derived durum wheat breeding lines

Durum wheat (Triticum turgidum L. var. durum) is used predominantly for pasta products, but there is increasing interest in using durum for bread-making. The goal of this study was to assess the bread-making potential of 97Emmer19, an Emmer wheat (Triticum turgidum L. var. dicoccum) and in breeding lines derived from crosses of 97Emmer19 with adapted durum wheat cultivars. 97Emmer19 and its progeny were evaluated in 2005 and 2006 along with five durum wheat cultivars. Three bread wheat (Triticum aestivum L.) cultivars were included as checks to provide a baseline of bread making quality observed in high quality bread wheat cultivars. 97Emmer19 exhibited higher LV than all the durum wheat checks and approached the LV achieved with the bread wheat cultivar ‘AC Superb’. Breeding lines derived from 97Emmer19 had higher LV than those of the durum wheat checks, confirming that this trait was heritable. In general, durum wheat cultivars with elevated gluten strength and/or increased dough extensibility were noted to have higher LV. Dough extensibility appeared to be a more critical factor as gluten strength increased. These results indicate that there is potential to select for genotypes with improved baking quality in durum breeding programs.     

Effect of wheat germ flour addition on wheat flour,dough and Chinese steamed bread properties

Wheat germ flour (WGF) has been developed as a functional food ingredient with high nutritional value. In this study, WGF was applied in steamed bread-making in order to improve the quality of Chinese steamed bread (CSB). Partial substitution of wheat flour with WGF at levels of 3%, 6%, 9% and 12% (w/w) was carried out to investigate physicochemical properties of blends and their steaming performance. Falling number (FN) values of composite flours ranged from 199 to 223 s. Viscosity analysis results showed that wheat flour mixed with WGF had higher pasting temperature and lower viscosities. Dough rheological properties were also investigated using farinograph and extensograph. The addition of WGF diluted the gluten protein in dough and formed weak and inextensible dough, which can be studied by scanning electron microscope (SEM) analysis. CSB made with WGF had significantly lower volume, specific volume and higher spread ratio. The sensory acceptability and physicochemical quality of CSB were improved with the application of a low level of WGF (3% and 6%). However, results showed that a high level of WGF over 9% is not recommended because of unsatisfactory taste. As a whole, addition of appropriate level of WGF in wheat flour could improve the quality of CSB.     

面包烘焙品质与小麦品质性状的相关性

为了了解适宜的面包小麦的品质指标范围，对58个小麦品种(系)的面包烘焙品质与小麦品质性状的相关性进行了分析与研究，将58个品种(系)的面包总评分分为三个梯度与小麦品质性状进行比较，结果表明，面包总评分和面包体积与蛋白质含量、湿面筋含量、沉淀值、吸水率、延伸性呈显著正相关，与抗延阻力相关不显著；面包芯平滑度与蛋白质含量、湿面筋含量、沉淀值、形成时间呈显著正相关；纹理结构与蛋白质含量、湿面筋含量、沉淀值、延伸性呈显著正相关；面包弹柔性与蛋白质含量呈显著正相关；与其它指标相关性不显著．