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.     

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.     

Studies on the baking properties of wheat: Pigeonpea flour blends

Pigeonpea flour was substituted at levels of 0, 5, 10, 15,20, 25% to wheat flour and whole wheat meal for bread andChapatti making, respectively. Blends were prepared up to50% for cookie making. Increasing levels of pigeonpeas inthe blends significantly increased the protein and mineralcontent of the baked products. The bread from 10%pigeonpea flour blend with 2–3% vital gluten and 0.5%SSL had high loaf volume and loaf quality. Blends containing 15% pigeonpea flour were acceptable for Chapatti and 30% pigeonpea flour with 0.25% SSL wereacceptable for cookie making.     

Accelerated ageingof wheat grains: Part I- Influence on rheological properties of wheat flour

Natural ageing is defined as handling and storage of freshly harvested grain for several years under storage condition to achieve suitable flour quality after milling. Accelerated ageing of wheat which is obtained using higher temperature during a specific storage time under controlled relative humidity may improve the quality of wheat flour. The present study addresses the effect of accelerated ageing on the rheological properties of wheat flour produced by freshly harvested wheat. The process of accelerated aging was performed by three different factors including rise in wheat moisture content (16, 18 and 20% w/w), control of storage temperature (30, 40 and 50°C) and control of the storage time (2, 5 and 8 days) using a central composite design. After the grain milling, rheological properties of wheat flour of different treatments were studied. Results indicated that promoting the storage time to 8 days and temperature up to 40°C could improve rheological properties such as dough stability, dough development time and farinograph quality number. This phenomenon may be due to oxidation and rearrangement of disulfide bonds resulting in increasing strength and improving flour quality. Increasing moisture content and storing in higher temperatures resulted in weakening rheological properties.     

Effect of medium hydrostatic pressure on the properties of wheat flour main biopolymers

In our work, the effect of medium hydrostatic pressure on the properties of wheat flour's main ingredients, starch and proteins, is presented and discussed. The symbiotic effect of the different constituents via size exclusion chromatography, water binding, gelatinization experiments as well as atomic force microscopy measurements and X-ray diffraction is elucidated. From results of size exclusion chromatography and protein content analysis, prolamin fractions seemed to be most sensitive to pressure. Hydrostatic pressure, however, had a significant influence on the amount of bound water and gelatinization enthalpy, especially at moderate pressures and higher temperatures. In this case, an optimal interaction between macromolecules and water occurs. This was also confirmed by atomic force microscopy images and X-ray diffraction patterns. Amorphous and crystalline regions of starch granules were modified, depending on pressure and temperature. At medium pressure (200 MPa), water was pressed into the starch cavities remaining there, whereas higher pressure (600 MPa) led to complete flattening of the surface. With X-ray diffraction, it was shown that medium pressure had nearly no effect on molecular structure, whereas higher pressure caused thermal-like molecular modifications.     

Cellular structure and rheological properties of shaped fermented wheat flour dough

Among the various operations of the breadmaking chain, the impact of shaping on dough cellular structure has scarcely been studied. In this work, wheat flour dough has been laminated under different roll gap conditions δ(mm)= (2,5, 10, 20, ∞). Rheological properties were measured under large and small strains, by lubricated squeezing flow test and dynamic thermomechanical analysis, respectively. Laminating has a limited effect on the elongational viscosity of the dough. However, the minimum value of the ratio of storage modulus reached for gap δ = 5 mm suggests that gluten network structuration is improved in this case. The kinetics of porosity and shape ratio of fermenting laminated doughs were calculated from image analysis of dough follow-up during proofing. They showed that stability is improved for δ = 5 mm. Finally, Xray tomography experiments, performed on laminated rolled dough during proofing, confirmed that the main changes can be attributed to an increase of cellular homogeneity at δ = 5 mm, reflected by lower median gas cell size and less spread size distributions.     

Comparison of small-scale and large-scale mixing characteristics: Correlations between small-scale and large-scale mixing and extensional characteristics of wheat flour dough

Mixing measurements provide valuable information about dough strength and stability (STAB) traits. These measurements are important in milling and baking operations, and for varietal selection in wheat breeding programmes. There are several techniques with different sample sizes used for measuring these traits so there is interest in examining the agreement between methods in terms of genotypic (varietal) rankings. This issue has been investigated by using two different mixing methods, a small-scale Mixograph (2 g) and large-scale Farinograph (50 g) using data from a doubled haploid population (190 lines) from a Chara (excellent dough strength)×WW2449 (poor dough strength) cross. The cross was grown in a field trial at the Wagga Wagga Agricultural Institute (WWAI) in 2000. Eleven mixing traits were measured and compared according to a statistical design. The estimated genetic correlation matrix for six of the 11 mixing traits, dough development time (DDT), STAB, mixing tolerance index (MTI), maximum bandwidth (MBW), bandwidth at peak resistance (BWPR) and peak resistance (PR) revealed that for these dough-strength-related parameters, both methods were measuring equivalent traits, although individual parameters had widely different coefficients of variation. In this population, PR was correlated with the extensibility trait length determined by large-scale extension testing. None of the large-scale or small-scale mixing traits was an effective predictor of the small-scale extensibility parameter extensibility at Rmax (Ext_Rmax). The data verified that small-scale Mixograph tests are a robust and efficient alternative to large-scale Farinograph tests for both commercial breeding and research.     

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.     

Impact of re-grinding on hydration properties and surface composition of wheat flour

The combination of two analytical methodologies (water vapor sorption isotherm by using the DVS and chemical surface composition by using the XPS) has been used to enhance the understanding of the impact of re-grinding on the wheat flour hydration mechanism. A controlled atmosphere microbalance was used to construct water sorption isotherms at 25 °C of different samples of wheat flours obtained by successive re-grinding of native wheat flour.     

Physical properties of wheat flour composites dry-coated with microparticulated soybean hulls and rice flour and their use for low-fat doughnut preparation

Air-classified wheat flour was dry-coated with microparticulated rice flour (30%, db) and/or microparticulated soybean hulls (up to 10%, db) using a hybridization system, and the physical properties of the dry-coated wheat flour were examined. The composite wheat flours exhibited the higher water-holding capacity but lower swelling power and oil-holding capacity than their counterpart mixtures. In pasting viscosity, the composites of wheat and rice flours had substantially lower values for peak viscosity and breakdown than did pure wheat flour. The incorporation of soybean hulls to the composites of wheat and rice flours further reduced the peak viscosity. The composites with rice flour and soybean hulls showed slightly higher melting (gelatinization) temperatures but lower melting enthalpy compared to the counterpart mixtures. By using the composite flours for the deep-fat fried doughnut preparation, the oil uptake could be substantially reduced by approximately 30%, in comparison to pure wheat flour or the mixture samples. The composite wheat flours with microparticulated rice flour and soybean hulls produced dough matrices with improved compactness and cell structure, which were attributed to the reduced fat uptake during frying.     

Physical properties of wheat flour composites dry-coated with microparticulated soybean hulls and rice flour and their use for low-fat doughnut preparation

Air-classified wheat flour was dry-coated with microparticulated rice flour (30%, db) and/or microparticulated soybean hulls (up to 10%, db) using a hybridization system, and the physical properties of the dry-coated wheat flour were examined. The composite wheat flours exhibited the higher water-holding capacity but lower swelling power and oil-holding capacity than their counterpart mixtures. In pasting viscosity, the composites of wheat and rice flours had substantially lower values for peak viscosity and breakdown than did pure wheat flour. The incorporation of soybean hulls to the composites of wheat and rice flours further reduced the peak viscosity. The composites with rice flour and soybean hulls showed slightly higher melting (gelatinization) temperatures but lower melting enthalpy compared to the counterpart mixtures. By using the composite flours for the deep-fat fried doughnut preparation, the oil uptake could be substantially reduced by approximately 30%, in comparison to pure wheat flour or the mixture samples. The composite wheat flours with microparticulated rice flour and soybean hulls produced dough matrices with improved compactness and cell structure, which were attributed to the reduced fat uptake during frying.     

Predicting hot-press wheat tortilla quality using flour,dough and gluten properties

A cost-effective, faster and efficient way of screening wheat samples suitable for tortilla production is needed. This research aimed to develop prediction models for tortilla quality (diameter, specific volume, color and texture parameters) using grain, flour and dough properties of 16 wheat flours. Another set of 18 samples was used to validate the models. The prediction models were developed using stepwise multiple regression. Dough rheological tests had higher correlations with tortilla quality than grain and flour chemical tests. Mixograph mixing time and dough resistance to extension (from extensibility test using a texture analyzer) were correlated best with tortilla quality, particularly tortilla diameter (r = −0.87 and −0.86 respectively, P < 0.01). Insoluble polymeric proteins (IPP) and gluten index were significantly correlated with tortilla diameter (r = −0.70 and −0.67 respectively, P < 0.01) and specific volume (r = −0.73, P < 0.01). Tortilla diameter was the quality parameter best explained (R² = 0.86) by the prediction models using mixing time and dough resistance to extension. Rheological parameters such as rupture distance and maximum force were also successfully predicted. These prediction models, developed from linear equations, will be an easy and fast tool for breeders to advance or eliminate wheat lines specifically bred for tortilla production.     

Effect of microbial transglutaminase on the rheological and thermal properties of insect damaged wheat flour

Proteases in insect damaged wheat disrupt grain protein structure. Transglutaminases catalyse the formation of covalent linkages between protein chains and can be used to restore the properties of the damaged proteins. The effect of increasing transglutaminase levels on the viscoelastic behaviour and thermal stability of damaged wheat was investigated. The results indicate that transglutaminase treatment leads to a more resistant and less extensible dough. Differential scanning calorimetry revealed that the transglutaminase treatment brings the thermal stability of the damaged wheat close to that of undamaged wheat. However, it is necessary to optimise the level of transglutaminase used to obtain the optimum response.     

Both genetic and environmental conditions affect wheat grain texture: Consequences for grain fractionation and flour properties

This review summarizes the results of studies on near-isogenic common wheat lines differing in the Pinb-D1 allele encoding puroindoline B or durum wheat into which both wild-type puroindoline genes were introduced. The material was grown in different environments to evaluate the respective effect of puroindoline genes or of the environmental factors on grain characteristics and milling behavior.Environmental conditions were found to impact grain porosity (=1/vitreousness) and the presence of both wild-type puroindoline genes was found to reduce the vitreousness threshold under 60%. Hardness measurements with single kernel characterization system were found to differ from near-infrared reflectance spectroscopy analysis and were linearly related to vitreousness but differently depending on the puroindoline allele carried.Puroindoline genes were found to play a major role in the grain porosity, breaking energy, size of generated particles and in the concentration of phytic acid and damaged starch into flour whereas vitreousness introduced variations in the ability to break and in the level of damaged starch.Finally, the highest flour yield is obtained from either vitreous common wheat grains carrying the wild-type puroindoline alleles or carrying mutated alleles and displaying low vitreousness. This result was confirmed using common French wheat cultivars whose puroindoline genes were identified.     

Modification of protein structure and dough rheological properties of wheat flour through superheated steam treatment

Native (NF, 13.5% w.b) and moistened (MF, 27% w.b) wheat flours were treated with superheated steam (SS) at 170 °C for 1, 2 and 4 min, and their protein structure as well as dough rheological properties were analyzed. Confocal laser scanning microscopy (CLSM) and SDS-PAGE patterns indicated the formation of protein aggregates with reduced SDS extractability after treatment. Farinograph and dynamic rheometry measurements showed that the strength as well as elastic and viscous moduli of the dough made from SS-treated flours progressively increased with SS treatment time. And both the improvements were more pronounced for superheated steam-treated moistened flours (SS-MF) than for superheated steam-treated native flours (SS-NF). Size-exclusion high performance liquid chromatography (SE-HPLC) analysis demonstrated that dough rheological parameters have positive correlations with SDS unextractable polymeric proteins (UPP) contents. SS treatment on flours led to a transition of protein secondary structures to more ordered form (α-helix and β-sheet). Additionally, free sulfhydryl (SH) contents decreased after treatment, which implied that disulfide bonds accounted for protein extractability loss and dough rheological properties improvement. Elevated moisture level promoted the modification of both protein structure and dough behaviors of flours during SS treatment.