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.     

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.     

PCR method for the detection and identification of cultivars of rice flours used in yeast leavened breads containing both wheat and rice flours

The identification of cereal grain sources in yeast leavened breads is challenging because of the mixtures of DNA from yeast and mixtures of related grains. DNA is decomposed during the fermentation and bread consists of not only rice but also wheat, yeast, sugar, butter, shortening etc.     

Effect of high molecular weight glutenins and rye translocations on soft wheat flour cookie quality

The influence of high molecular weight glutenin subunits (HMW-GS) on wheat breadmaking quality has been extensively studied but the effect of different Glu-1 alleles on cookie quality is still poorly understood. This study was conducted to analyze the effect of HMW-GS composition and wheat-rye translocations on physicochemical flour properties and cookie quality of soft wheat flours. Alleles encoded at Glu-A1, Glu-B1 and Glu-D1 locus had a significant effect over physicochemical flour properties and solvent retention capacity (SRC) profile. The null allele for Glu-A1 locus presented the highest cookie factor observed (CF = 7.10), whereas 1BL/1RS and 1AL/1RS rye translocations had a negative influence on CF. The three cultivars that showed the highest CF (19, 44 and 47) had the following combination: Glu-A1 = null, Glu-B1 = 7 + 8, Glu-D1 = 2 + 12 and no secalins. Two prediction equations were developed to estimate soft wheat CF: one using the HMW-GS composition and the other using physicochemical flour parameters, where SRCsuc, SRC carb, water-soluble pentosans, damaged starch and protein turned out to be better CF predictors. This data suggests that grain protein allelic composition and physicochemical flour properties can be useful tools in breeding programs to select soft wheat of good cookie making quality.     

Comparison of quality of refined and whole wheat tortillas

The use of whole wheat flour instead of refined flour significantly improves the nutritional profile of flour tortillas. However, whole and refined flours differ in properties and in how they process, thus needing process modifications to get the desired product quality. To understand these differences, refined and whole wheat flours, dough and tortillas were evaluated and compared for physical and rheological properties. Overall, whole wheat flour required more water (59% of flour weight) than refined wheat (53%) to make machineable dough. Refined flour doughs were more extensible and softer than whole wheat flour doughs, thus easier to process. Whole wheat flour tortillas were larger, thinner and less opaque than refined flour tortillas. In general, refined wheat tortillas were more shelf-stable than whole wheat tortillas. Smaller particle size and less fiber in the refined wheat flour mainly contributed to the observed differences. Among the whole wheat samples, tortillas from strong flours had excellent shelf-stability, which must be considered when whole wheat tortillas are processed. This will minimize the need to add vital wheat gluten or other dough strengtheners.     

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.     

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.     

Dough rheology and bread quality of wheat-chickpea flour blends

In this study, partial substitution of wheat flour with chickpea flour at the levels of 10, 20 and 30% was carried out to study their rheological and baking performance. Chickpea flour addition increased the water absorption and dough development time (p < 0.05), while, the extensibility of dough and the resistance to deformation were reduced. Regarding dough stability, it appears that 10% chickpea exhibited higher stability and resistance to mechanical mixing values than the control, while it decreased as the substitute level increases from 20% to 30%. The dough surface of the wheat dough and the blend with 10% was classified as “normal”, however the blend with 20% and 30% produced “sticky” dough surface. The presence of chickpea flour in dough affected bread quality in terms of volume, internal structure and texture. The color of crust and crumb got progressively darker as the level of chickpea flour substitution increased. While the substitution of wheat flour with 10% chickpea flour gave loaves as similar as control.     

Molar fractions of high-molecular-weight glutenin subunits are stable when wheat is grown under various mineral nutrition and temperature regimens

Molar fractions of the high-molecular-weight glutenin subunits (HMW-GS) were determined for flour from bread wheat (Triticum aestivum L. cv Butte86) produced under 13 different combinations of temperature, water and mineral nutrition. Albumins, globulins and gliadins were removed from the flour by extraction with 0.3 M NaI in 7.5% 1-propanol. Total HMW-GS were recovered by extracting the remaining protein with 2% SDS and 25 mM DTT. Individual HMW-GS were then separated and quantified by RP-HPLC. Constant molar fractions for the five HMW-GS were maintained under all environmental conditions, despite large differences in duration of grain fill, total protein per grain, flour protein percentage, and total HMW-GS per grain. Similar molar fractions were found for five other US wheat varieties. The Bx7 subunit accumulated to the highest level at 30% of total HMW-GS. The Dx and Dy subunits were present in smaller but nearly equal proportions, 22% and 23%, respectively, and the Ax and By subunits were the least abundant, 14% and 12%, respectively. Although the amounts of HMW-GS per unit of flour are strongly affected by environment, the different subunits respond so similarly to external conditions that their final proportions appear to be determined mainly by genetic factors.     

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.     

Effects of potato/wheat flours ratio on mixing properties of dough and quality of noodles

The effects of potato flour/wheat flour (PF/WF) ratio on the mixing properties of dough and the quality of noodles were investigated. Substitution of wheat flour with potato flour caused the increases in the water absorption and the protein weakening value (C1-C2) of formulated flours, as well as the decrease in the corresponding dough mixing parameters including dough development time (DDT), dough stable time (DST), initial mixing time (C2), maximum torque during heating (C3), minimum torque of hot paste (C4) and the amount of retrogradation (C5-C4), indicating that the addition of PF weakened dough strength but improved degradation resistance. The textural, cooking, sensory characteristics and microstructure of noodle samples were evaluated. The results indicate that adhesiveness, springiness, broken ratio and cooking lose increased progressively with increasing PF content while the score of sensory evaluation continued to decrease. However, hardness, cooking yield and optimum cooked time for the samples of PF content range from 10% to 20% showed a distinctive variation. Environmental scanning electron microscopy (ESEM) confirmed changes in noodle microstructure as PF addition affected gluten network development. In general, noodles with PF content below 40% were acceptable.     

Comparison of different rice flour- and wheat flour-based butter cookies for acrylamide formation

Acrylamide (AcA) contents of different rice flour- and wheat flour-based butter cookies baked at 130 °C for 20, 55, or 90 min were investigated. AcA contents of different flour-based cookies increased with baking time. Color parameters in terms of CIE L*, b*, C*, and ΔE values showed significant opposite correlation to the AcA formation in each of the raw flour cookie. The cookies based on white rice flour had the lowest AcA contents ranging from not detectable (ND) to 204 μg/kg, followed by cookies based on brown rice flour (ND to 450 μg/kg), white wheat flour (155 μg/kg to 661 μg/kg), and whole wheat flour (306 μg/kg to 982 μg/kg). Considerably lower AcA levels were found in the rice flour-based cookies than in the wheat flour-based cookies, as well as in the milled flour-based cookies than in the whole-grain cookies. Although the flour source was considered to play a primary role in determining the AcA content, AcA content was apparently not dependent on the quantities of reducing sugars and free asparagine in the starting raw flour and cookies during baking. In summary, given its reducing potential for AcA formation, rice flour could be used in the production of cookies safe from heat-induced contaminants.     

Extensograph curve profile model used for characterising the impact of dietary fibre on wheat dough

A seven-parameter regression model was developed to determine changes in the shape of the Brabender extensograph curve as a result of supplementation of wheat dough with carob fibre and oat wholemeal. The shape of the curve, close to an inverted parabola, was well described by a cubic polynomial function. The exceptions were the initial and final sections of the curve, for the representation of which two exponential functions were used. Under the effect of the fibre-rich additions, the strongest variation was observed in the polynomial function parameters describing the slope and deflection of parabolic arms of the extensograph curve and the position of its peak, while the parameters showing the final course of the curve were subject to only slight changes. The reactivity of the additions during dough proving had a much stronger effect on the model parameters than on the variation of the maximum resistance and extensibility of the dough. The results indicate that the proposed model can be a useful tool for improving the analysis of extensional behaviour of bread dough.     

Effect of glucose oxidase,transglutaminase, and pentosanase on wheat proteins: Relationship with dough properties and bread-making quality

Glucose oxidase (Gox), transglutaminase (TG), and pentosanase (Pn) were investigated for their effect on bread quality. The changes introduced in wheat protein by the action of these enzymes were analysed to explain dough behaviour. Gox treatment decreased free sulphydryl groups (SHf), increased glutenin macropolymer contents, and modified the electrophoretic pattern of protein fractions. Gox modified mainly albumin, globulin, and glutenin, forming large protein aggregates. These modifications explained the high strength of the dough and the low bread specific volume of samples with Gox. TG treatment modified solubility in SDS of protein and decreased glutenin macropolymer content. However, it formed large protein aggregates. The new cross-linking bonds introduced by this enzyme were different to S–S bonds and, consequently, the dough was less extensible and showed high resistance. Pn treatment increased water soluble pentosan content. Moreover, in these samples a tendency to increase SHf content was observed. In addition, Pn increased protein solubility in isopropanol, which indicates that the reduction of pentosans size decreases steric impediment of insoluble pentosans, thus increasing interaction among protein and making their extraction easier. These changes at the microscopic level allowed explaining the formation of softer dough and the production of higher specific volume in breads with Pn.     

Effects of pressure treatment of hydrated oat,finger millet and sorghum flours on the quality and nutritional properties of composite wheat breads

Breadmaking achievement using grains alternative to wheat and rye is a challenging task for cereal technologists, since most of the available innovative breads are characterised by poor crumb and crust characteristics, slight flavour and fast staling. To improve texture, mouth-feel, acceptability and shelf-life of breads prepared by using minor and/or under-utilised cereals, gluten and/or polymeric substances that mimic the viscoelastic properties of gluten, are required. Recent studies reported that high hydrostatic pressure (HP) treatment may represent an efficient non-thermal technique to promote the dough structure formation of composite cereal matrices. In the present study the effects of HP on the techno-functional and nutritional properties of oat-, millet-, and sorghum- based breads were evaluated compared to their unpressured- and gluten-added conventionally made counterparts. HP-treated (350 MPa, 10 min) wheat, oat, millet and sorghum batters were added to the bread recipe, replacing 50%, 60% and 40% of untreated wheat flour, respectively. Data from bread analyses revealed non significant physico-chemical impairment, and superior nutritional and sensory profiles in most quality features when HP treatment was applied to dough batters, compared with conventional/gluten-added samples. Specifically, HP breads deserved better sensory scores and exhibited higher antiradical activities despite a reduction in specific volume (wheat and oat) and faster staling kinetics (millet and sorghum) that were explicit in some composite samples.     

Chemical composition and functional properties of blends of maize and bambara groundnut flours for cookie production

Chemical composition and functional properties of flour blends containing various levels of maize (100–0%) and bambara groundnut (0–100%) were studied. The resultant blends were high in protein, carbohydrate and caloric value. The blends contained fair amounts of Ca, P and K but were low in Na and Fe. The oil and water absorption capacities of the blends were fairly high ranging from 3.65 to 3.81 g oil/g sample and 3.40 to 3.80 g water/g sample, respectively. The gelation concentration of the blends tended to increase with increase in amount of maize flour in the blend. On the other hand, increasing the level of maize flour in the blends considerably reduced the foaming capacities of the blends. The flour blends had good emulsifying properties. Cookies prepared from the blends contained proteins ranging from 10.9 to 21.65% The cookies had good spread and were significantly lighter than the wheat control cookies. Sensory evaluation scores for cookies showed that the best level of combination was 75% maize flour and 25% bambara groundnut flour.     

Changes in the content of free sulphydryl groups during postharvest wheat and flour maturation and their influence on technological quality

The main aim of this study was to determine the changes in free sulphydryl content during postharvest wheat and flour maturation. The content of free sulphydryl groups was determined from wet gluten over 50 days of wheat postharvest maturation and over 14 days of flour maturation by varying incubation temperatures (30 and 37 °C) and incubation times (0, 45, 90 and 135 min). The amount of free sulphydryl groups increased during postharvest wheat and flour maturation as well as with the increase in temperature and gluten incubation time. The additional aim of this study was to find the interrelation between the content of free sulphydryl groups and selected parameters of technological quality by means of Principal Component Analysis. During wheat/flour maturation, the strengthening of protein structure was observed manifested by the increase in gluten index and Mixolab protein network weakening (C2), and changes in dough resistance as well. The incubation temperature of 37 °C affected the weakening of protein structure manifested by the decrease in gluten index and resistance, and increase in extensibility. Strong differentiation of examined varieties in terms of selected quality indicators was observed upon pre-defined maturation period, probably due to the expression of their intrinsic properties.     

Changes in the content of free sulphydryl groups during postharvest wheat and flour maturation and their influence on technological quality

The main aim of this study was to determine the changes in free sulphydryl content during postharvest wheat and flour maturation. The content of free sulphydryl groups was determined from wet gluten over 50 days of wheat postharvest maturation and over 14 days of flour maturation by varying incubation temperatures (30 and 37 °C) and incubation times (0, 45, 90 and 135 min). The amount of free sulphydryl groups increased during postharvest wheat and flour maturation as well as with the increase in temperature and gluten incubation time. The additional aim of this study was to find the interrelation between the content of free sulphydryl groups and selected parameters of technological quality by means of Principal Component Analysis. During wheat/flour maturation, the strengthening of protein structure was observed manifested by the increase in gluten index and Mixolab protein network weakening (C2), and changes in dough resistance as well. The incubation temperature of 37 °C affected the weakening of protein structure manifested by the decrease in gluten index and resistance, and increase in extensibility. Strong differentiation of examined varieties in terms of selected quality indicators was observed upon pre-defined maturation period, probably due to the expression of their intrinsic properties.     

GlutoPeak parameters of whole wheat flours for gluten quality evaluation in soft wheat breeding programs

In soft wheat breeding programs, the gluten strength of flours from specific genotypes is determined by various chemical and rheological tests. Based on such tests, the experimental wheat lines with very weak flour gluten are typically selected for the production of soft-dough biscuits, while the lines with medium gluten strength and extensibility are reserved for hard-dough biscuits. Often, the genotypes having high gluten strength are removed from such breeding programs. In the present study, the usability of the GlutoPeak tester on whole wheat flour samples was investigated for assessing the gluten strength of soft wheat breeding materials. In the study, 25 soft wheat genotypes, grown in seven locations for three years, were categorized by commonly used gluten-quality-related parameters. Based on the results of the study GlutoPeak whole wheat flour PMT values ranging from 30.0 to 50.0 s and AM values from 15.0 to 20.0 GPU were found to be suitable for soft-dough biscuit products, whereas the values between 40.0 and 60.0 s and 20.0 and 23.0 GPU were appropriate for hard-dough biscuit products. The genotypes exhibiting AM values > 24.0 GPU and PMT values > 60.0 s were judged to have too-strong gluten, and thus eliminated from the breeding program. The gluten aggregation energy (AGGEN), and the torque after the maximum torque (PM) values were only useful and applicable to flours for soft-dough products. The maximum torque (BEM) values were not effective in discriminating against the genotypes. The results of this study demonstrated that the GlutoPeak whole wheat PMT and AM parameters can be recommended as quick and accurate parameters especially for early generation screening with small-scale tests in soft wheat improvement programs.     

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.