Wheat (Triticum aestivum L.) puroindoline functionality in bread making and its impact on bread quality

Wheat puroindolines (PINs) spontaneously adsorb at air/water interfaces and show excellent foaming properties. They can positively impact bread quality, in which the formation of stable foam is important for product quality. The impact of endogenous PINs on bread quality was studied by preparing gluten–starch blends from isolated gluten and starch fractions with different PIN levels, which allowed largely retaining the interaction between PINs and flour components. Our results indicate that blends with high PIN levels yielded more homogeneous crumb structures with fine gas cells than bread made with blends containing medium or low PIN levels. However, the mechanism by which PINs exert this crumb improving effect is not clear. Varying PIN levels impacted neither dough extensibility nor did it result in different PIN levels in dough liquor. Lipid removal yielded bread with a less homogeneous crumb gas cell distribution, indicating that lipids also are required to obtain good crumb structure.     

Key issues and challenges in whole wheat flour milling and storage

Whole wheat flour is increasingly popular as research continues to reveal the benefits of whole grains and the food industry offers more whole grain options for consumers. The purpose of this review is to address milling and shelf-life issues that are unique to whole wheat flour. No standard methods are available for whole wheat flour milling, resulting in very different bran particle sizes. Literature suggests that moderate bran particle size is the best for bread production, while small particle size is better for non-gluten applications. Shelf-life of whole wheat flour is shorter compared to white flour due to the presence of lipids and lipid-degrading enzymes. Lipolytic degradation leads to reduction in functionality, palatability and nutritional properties. Strategies to stabilize whole wheat flour have focused on controlling lipolytic enzyme activity and have marginally succeeded.     

Effect of barley and oat flour types and sourdoughs on dough rheology and bread quality of composite wheat bread

The potential of sourdough to improve bread quality of barley and oat enriched wheat breads may depend on the characteristics of the added flour (cereal type, variety, extraction rate). We compared the effect of different barley flours and oat bran (substitution level 40%), unfermented and as sourdoughs (20% of total flour), on composite wheat dough and bread characteristics by combining empirical rheological analyses (DoughLab, SMS/Kieffer Dough and Gluten Extensibility Rig) with small-scale baking of hearth loaves. Whole grain barley flour sourdough increased resistance to extension (Rmax) of the dough and improved the form ratio of hearth loaves compared to unfermented whole grain barley flour. However, sourdough showed little effect on the breads prepared with sifted barley flour or oat bran. The breads made with oat bran showed highest bread volume, lowest crumb firmness and highest β-glucan calcofluor weight average molecular weight (MW). The heat treatment of oat bran inactivated endogenous enzymes resulting in less β-glucan degradation. High MW β-glucans will increase the viscosity of the doughs water phase, which in turn may stabilise gas cells and may therefore be the reason for the higher bread volume of the oat bran breads observed in our study.     

Properties of whole grain wheat flour and performance in bakery products as a function of particle size

The aim of this study was to evaluate the effect of particle size distribution on composition, properties rheological, pasting, microstructural and baking properties of whole grain wheat flour (WGWF) of three different particles sizes (194.9 μm, 609.4 μm and 830.0 μm). The quantification of free sulfhydryl groups (-SH) of WGWF samples, together with the effects observed in the behavior of the dough and bread showed that particle size influences the functionality of the gluten network in a differentiated way. Firmer and lower breads volume compared to refined wheat flour (RF) were correlated with the quality of the gluten network. In the sample of finer particles, more pronounced adverse effects in quality (dough rheology, bread volume and texture) compared to the medium and coarse particle size sample suggests that the larger contact surface and the increased release of reactive compounds due to cell rupture interact with the gluten-forming proteins changing their functionality.     

Lipids in bread making: Sources, interactions, and impact on bread quality

Lipids exhibit important functional properties in bread making, although they are present in lower levels than starch or protein. They originate from flour, in which they are endogenously present, or from added shortening and/or surfactants. This review discusses lipid sources and their interactions during the entire process of bread making from dough mixing to fermentation, proofing, baking and the stored product. The focus is on lipid interactions with starch and gluten proteins, their role in gas cell stabilisation and their impact on bread loaf volume, crumb structure and crumb firming. Widely accepted views on lipid functionality, although often opposing, are presented and critically discussed.     

Protein profiles and organoleptic properties of bread from wheat flour and full-fat or defatted fermented cocoa bean powder

This study has shown that the protein in bread may be quantitatively increased significantly by addition of full-fat or defatted cocoa powder to white flour. The recipe in which white flour is incorporated with up to 10 percent defatted cocoa powder gives bread that is nearly as well accepted as white bread, but with a significantly higher protein content than the latter. However, organoleptic acceptability drops with increasing percentage of cocoa supplementation. The bitter taste of theobromine, which is normally present in high amounts in cocoa bean, is thought to be responsible for this problem of poor acceptability of high cocoa breads. This problem will have to be addressed in order to enhance the scope of increasing bread protein by cocoa supplementation.     

Feature of air classification product in wheat milling: Physicochemical,rheological properties of filter flour

Wheat filter flours are by-products obtained from air-classification of wheat flour. Physicochemical and rheological properties of wheat filter flours were investigated in the present study. Average values of crude protein, gluten, lipid and damaged starch content of filter flours were higher than those of standard flours for the same batch. The positive correlation of particles with size <20 μm and damaged starch was found. Moreover, the filter flours had higher water absorption, stability time except head milling filter flour samples. Short peak time and low peak viscosity were also observed. Different composition of wheat filter flours may be an important factor influencing its properties. This study is very useful for exploring the utilization of wheat filter flours in the food industry.     

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.     

Agronomic characteristics, grain quality and flour rheology of 372 bread wheats in a worldwide core collection

A core collection of 372 accessions representative of worldwide hexaploid bread wheat diversity [Balfourier, F., Roussel, V., Strelchenko, P., Exbrayat-Vinson, F., Sourdille, P., Boutet, G., Koenig, J., Ravel, C., Mitrofanova, O., Beckert, M., Charmet, G., 2007. A worldwide bread wheat core collection arrayed in a 384-well plate. Theoretical and Applied Genetics 114, 1265–1275] was used to evaluate the available genetic diversity of agronomic and quality characteristics. The traits assessed during the vegetative period were date of ear-emergence, date of flowering, lodging, disease susceptibility and pre-harvest sprouting. Thousand kernel weight, test weight, grain hardness, grain protein content, pentosan viscosity and grain colour were also measured. The rheological properties of the derived white flours were estimated using mixograph and alveograph tests. For most of the traits, a wide phenotypic variation was observed across all the accessions. Several parameters (mixograph width parameters before and after peak time, alveograph dough tenacity and extensibility, near infrared measurements, like those for protein content, and absorbance measurements of palmitic acid and linoleic acid content) made it easier to discriminate between the cultivars. The largest ranges of variation were found in landraces and old cultivars rather than in more recent varieties. This is evidence that there is sufficient variability available for rare alleles, which have been eliminated in breeding modern varieties to be detected. Such a core collection will therefore be a useful resource for future genetic studies on wheat quality.     

Use of a global wheat core collection for association analysis of flour and dough quality traits

Flour and dough quality are very important breeding traits for wheat (Triticum aestivum L.) the selection of which would benefit from linked molecular markers. Association analysis allows the identification of genes or quantitative trait loci (QTL) related to target traits. The effectiveness of this approach depends on the availability of a densely genotyped population with large genetic variability for the traits of interest. Our objective was to identify chromosomal regions associated with flour and dough quality traits using a core collection built by maximizing the genetic diversity and phenotypic variability. We investigated the association of DArT, SSR and SNP markers with grain protein content, grain hardness, water-extractable arabinoxylan (WEAX) viscosity, wholemeal flour color and dough rheology.Out of 803 markers tested, 130 markers spread over the genome were associated with at least one trait, varying from 20 associated with WEAX viscosity to 60 associated with dough quality. Most chromosome regions known to determine wheat quality from the study of several bi-parental recombinant inbred lines were confirmed here and some new regions were identified. Associations were found for each trait studied, demonstrating that the core collection is a useful tool for QTL association mapping of these and other traits of interest.     

Effect of barley flour addition on the physico-chemical properties of dough and structure of bread

The effects of different percentages of barley flour (i.e. 0–25%) in wheat flours on the physico-chemical properties and structure of dough and bread were investigated. As the percentage of barley flour in mixed flour was increased, its protein and gluten contents decreased whereas the ash content and enzyme activity increased. The rheological characteristics of the four dough mixes were studied using Farinograph, Extensograph and Alveograph. The water absorption (p < 0.01) and stability (p < 0.05) decreased significantly as the percentage of barley flour increased, while no changes were observed in the extensibility and maximum heights. Significant differences were observed in the structural and physical properties as well as in the image analysis of breads. With the increase in the percentage of barley flour, the crumb apparent density decreased (p < 0.1) whereas the porosity (i.e., fraction to total volume) increased (p < 0.1). Overall, the shape and pore structure at 10% barley flour (W90B10) were similar to the pure wheat flour bread, while addition at 15 and 25% of barley flour (W85B15 and W75B25) showed more non-uniform and larger pores.     

Volume change of bread and bread crumb during cooling,chilling and freezing,and the impact of baking

During baking, bread dough undergoes an expansion followed by a slight contraction at the end of baking. The contraction during baking has been evidenced by some authors. However, there is a limited amount of literature about the contraction of the crumb during the chilling phase and also during the freezing phase in the case of freezing. A study has been carried out to better understand the impact of the baking degree on the contraction of the crumb during chilling after baking and during freezing. The volume of the samples has been evaluated with a laser volumeter. Breads (70 g dough) were baked until reaching 75 °C, 85 °C, 95 °C, 98 °C and then 98 °C for 10 min. Results showed that a longer baking resulted in a lower contraction of the bread. The volume change was between 25% and 2.5% for baking at 75 °C—0 min dwell and 98 °C—10 min dwell, respectively. The contraction was compared to the contraction of degassed bread crumb samples, which was more important. SEM pictures showed that the degree of baking also corresponded to a very different structure of the crumb. For the longer baking, the starch granules were fully gelatinized and no ghosts of starch granules were visible. The magnitude of the contraction was thus associated with the degree of baking and with the degree of starch granule destructuration.     

Impact of long-term frozen storage on the dynamics of water and ice in wheat bread

Frozen storage of bread has a substantial impact on the dynamics of water and ice in the crumb and crust. In this study, the impact was characterized using wheat bread stored at −18 °C for a long term of ∼4 months. The frozen bread incurred a considerable loss of the crumb water that migrated out and formed ice crystals on the bread surface. Such a moisture decrease underwent more rapidly for the bread stored without intact crust, suggesting the specific role of crust during frozen storage. Moisture also redistributed significantly within the frozen crumb, resulting in an elevated crumb heterogeneity of freezable water. This redistribution of freezable water was accompanied by a progressive recrystallization of the crumb-borne ice crystals, which were measured to grow into bulk sizes using a modified calorimetric procedure for analyzing the crumb samples at their as-frozen states.     

Combined effects of glucose oxidase,papain and xylanase on browning inhibition and characteristics of fresh whole wheat dough

In this study, a glucose oxidase (GOX), papain and xylanase combination was developed for fresh whole wheat dough for both browning inhibition and rheological improvement. Measurements of carotenoids extracted from enzyme-treated doughs showed that 0.001% (w/w) GOX could catalyze the oxidization of 40.0% carotenoids and thus cause a decrease of browning index (BI) by 5.20 during dough preparation. For 24 h browning inhibition, 0.010% (w/w) xylanase and papain individuals were able to separately act on the phenolic compounds and polyphenol oxidase, leading to lower BI rises (5.36 and 7.04, respectively) of doughs as compared to the BI rise (13.53) of the control dough; however, 0.020% GOX caused a higher BI rise (16.60) than control although it made BI decrease by 6.34 at 0 h. Rheological investigations on enzyme-treated doughs revealed that both xylanase and papain led to decreases of elastic (G′) and viscous modulus (G″) of doughs while GOX caused increases of G′ and G″. Therefore, an optimal combination composed of 0.010% (w/w) xylanase, 0.005% (w/w) papain and 0.002% (w/w) GOX was carried out using orthogonal experimental design by comparing BI rises in 24 h, which was also proved as a rheological improver for fresh whole wheat dough.     

Effect of the addition of extruded wheat flours on dough rheology and bread quality

Extruded wheat flours, due to their increased water absorption capacity, constitute an opportunity to increase bread output in bakery production. However extrusion may modify dough and bread characteristics. The aim of this study was to investigate the effect of the substitution of 5% of the wheat flour by extruded wheat flour (produced with different time-temperature extrusion treatments) on dough mixing, handling and fermentation behaviour and bread volume, shape, texture and colour. The RVA curves indicate that extrusion intensity increases with increasing temperature or water content. Water absorption capacity rises with increasing treatment intensity, but dough stability tends to decrease. Adding extruded flours decreases dough extensibility but increases tenacity and gas production. Differences in dough structure were observed on photomicrography, though there were no clear differences in bread quality. These results indicate that it is possible to obtain adequate dough and bread characteristics using dough with 5% extruded wheat flour.     

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.     

Effects of fermentation and heat treatments on bound-ferulic acid content and total antioxidant capacity of bread crust-like systems made of different whole grain flours

In this study, bread crust-like systems were prepared by heating (5, 15 and 30 min at 200 °C) freeze-dried fermented doughs obtained using different cereal grains. The flours of whole wheat, refined wheat, whole einkorn, whole rye, whole oat and whole maize were used. The effects of fermentation and heating on bound ferulic acid concentration and total antioxidant capacity were determined. Besides, high molecular weight fractions, containing also melanoidins formed in bread crust-like systems during heating were analyzed for their bound ferulic acid content and total antioxidant capacity. Increasing heating time at 200 °C also increased the amounts of high molecular weight fractions in the bread crust-like systems for all cereals. The total antioxidant capacity of bread crust-like samples increased significantly with heating time (p < 0.05). However, the opposite was true for the high molecular weight fractions of bread crust-like samples. Mean bound ferulic acid concentrations of different cereal flours were found to range between 78.3 mg/kg (for refined wheat) and 667.7 mg/kg (for whole einkorn). Heating had no significant effect on bound ferulic acid contents of bread crust-like systems. For all cereals, the highest concentrations of bound ferulic acid were detected in the high molecular weight fractions of bread crust-like systems heated at 200 °C for 5 min. However, bound ferulic acid concentrations significantly decreased in high molecular weight fractions as heating time increased (p < 0.05).     

Dough quality of bread wheat lacking α-gliadins with celiac disease epitopes and addition of celiac-safe avenins to improve dough quality

Celiac disease is a T-cell mediated immune response in the small intestine of genetically susceptible individuals caused by ingested gluten proteins from wheat, rye, and barley. In the allohexaploid bread wheat (Triticum aestivum), gluten proteins are encoded by multigene loci present on the homoeologous chromosomes 1 and 6 of the three homoeologous genomes A, B, and D. The effect of deleting individual gluten loci was analyzed in a set of deletion lines of T. aestivum cv. Chinese Spring with regard to the level of T-cell stimulatory epitopes (Glia-α9 and Glia-α20) and to technological properties of the dough including mixing, stress relaxation, and extensibility.     

Experimental data and modeling of the thermodynamic properties of bread dough at refrigeration and freezing temperatures

Thermodynamic properties of bread dough (fusion enthalpy, apparent specific heat, initial freezing point and unfreezable water) were measured at temperatures from −40 °C to 35 °C using differential scanning calorimetry. The initial freezing point was also calculated based on the water activity of dough. The apparent specific heat varied as a function of temperature: specific heat in the freezing region varied from (1.7–23.1) J g⁻¹ °C⁻¹, and was constant at temperatures above freezing (2.7 J g⁻¹ °C⁻¹). Unfreezable water content varied from (0.174–0.182) g/g of total product. Values of heat capacity as a function of temperature were correlated using thermodynamic models. A modification for low-moisture foodstuffs (such as bread dough) was successfully applied to the experimental data.