Study of the mechanism of improvement due to waxy wheat flour addition on the quality of frozen dough bread

Waxy wheat flour (WWF) was substituted for 10% regular wheat flour (RWF) in frozen doughs and the physicochemical properties of starch and protein isolated from the frozen doughs stored for different time intervals (0, 1, 2, 4 and 8 weeks) were determined to establish the underlying reasons leading to the effects observed in WWF addition on frozen dough quality. Using Nuclear Magnetic Resonance (NMR), Differential Scanning Calorimeter (DSC) and X-ray Diffraction (XRD) among others, the gluten content, water molecular state, glutenin macropolymer content, damaged starch content, starch swelling power, gelatinization properties, starch crystallinity and bread specific volume were measured. Compared to RWF dough at the same frozen storage condition, 10% WWF addition decreased dry gluten and glutenin macropolymer contents and T₂₃ proton density of frozen dough, but increased the wet gluten content, T₂₁ and T₂₂ proton density. 10% WWF addition also decreased damaged starch content, but increased starch swelling power, gelatinization temperature and enthalpy, crystallinity of starch and bread specific volume of frozen dough. Results in the present study showed that the improvement observed due to WWF addition in frozen dough bread quality might be attributed to its inhibition of redistribution of water molecules bound to proteins, increase in damaged starch content and decrease in starch swelling power.     

Comparison of structural features of reconstituted doughs affected by starches from different cereals and other botanical sources

Starch, as the main component of flour products, determines the physicochemical properties of dough. This work investigated the relationship of the physical properties of seven types of starches from various cereals with the structural features of reconstituted dough. Results of mixing and tensile properties analysis and scanning electron microscopy displayed that rice reconstituted flour exhibited maximum water absorption; pea reconstituted flour had higher dough stability; sweet potato dough had higher tensile resistance; highland barley dough had the greatest extensibility. Moisture distribution analysis revealed that various model dough showed remarkably different water distribution, which was distributed at T₂₁ (0.07–0.11 ms), T₂₂ (0.8–2.66 ms) and T₂₃ (10.0–20.82 ms). Correlation analysis indicated that large starch granules associated with good dough stability; amylose content of starch positively affected tensile resistance of dough; crystallinity of starch showed negative effects on water absorption; starch with higher crystallinity associated with greater dough stability.     

Study of the impact of wheat flour type,flour particle size and protein content in a cake-like dough: Proton mobility and rheological properties assessment

The study of food products is always a challenge due to the number of components involved and the interactions that may occur between them. Water is a particular ingredient which interacts with all hydrophilic compounds, although affinities may differ for limiting water amount. During this study, results obtained using ¹H NMR on cake dough were compared in terms of the effects of flour type (soft or medium hard), the addition of gluten (5%–20%) and the use of soft flour fractions (flour particle fractions smaller or larger than 50 μm). T₂ values and the signal intensities of different proton populations were studied as a function of the wheat protein contents of dough samples. Physicochemical characterization methods were used to better understand how the origin and particle size of flour might impact the hydration properties and mobility of a model system. Increasing the protein content in dough samples was related to an increase of the mobility of fat protons and of the least mobile proton population (relaxation times ranging from 175 to 180 ms and from 5 to 7 ms, respectively).     

Effect of bran on bread staling: Physico-chemical characterization and molecular mobility

High fibre breads were produced with the addition of durum wheat bran fractions (regular bran and a fraction extracted from the most internal bran layer) and their physico-chemical properties and water status were characterised during storage. Bran enriched breads exhibited similar properties during storage, they were harder, less springy and less cohesive than the control. Water status was strongly affected by bran addition, independently of bran composition: water activity, moisture and frozen water content (measured by Differential Scanning Calorimetry) were generally higher in the bran samples than in the control bread during storage. Amylopectin retrogradation was significantly larger in the presence of bran fractions. ¹H NMR mobility (T₂ number of populations and relaxation times) was different in the high fibre breads as compared to the control sample. The changes in protons mobility observed upon storage indicated an influence of bran on water/gluten/starch molecular domains and their dynamics, that may have affected the development of the gluten network resulting in different textural properties.     

Mixing history affects gluten protein recovery, purity, and glutenin re-assembly capacity from optimally developed flour–water batters

Batters, from three wheat cultivars, were mixed up to their maximal consistency (t_peak) at different mixing speeds (N) and flour/water ratios [Auger, F., Morel, M.H., Lefebvre, J., Dewilde, M., Redl, A., 2008. A parametric and microstructural study of the formation of gluten network in mixed flour–water batter. Journal of Cereal Science 48, 349–358]. Gluten and starch were extracted from those batters using a process which included two successive steps: dilution and sieving. In order to reveal the specific influence of the mixing step, a standardized gentle washing and sieving procedure was selected. Mixing the batters at t_peak guaranteed a high and stable gluten protein recovery (ca. 82%) irrespective of mixing conditions. SE-HPLC analysis of protein, from flours and batters sampled at t_peak, demonstrated that mixing led to the almost total breakdown of the unextractable glutenin polymers (ca. 80%), whereas their re-assembly occurred during gluten extraction. The extent of glutenin re-assembly in gluten was influenced by the batter mixing history and was mainly related to the number of mixing rotations (N.t_peak). Gluten protein contents were also found related to N.t_peak. We proposed that the leaching of starch from the batter during gluten extraction was controlled by the elasticity of the protein network, i.e. the gluten content in unextractable glutenin. An innovating scheme relating the glutenin re-assembly capacity to the irreversible thiol protein oxidation is proposed.     

Substrate selectivity and inhibitor sensitivity affect xylanase functionality in wheat flour gluten–starch separation

Addition of xylanases (EC 3.2.1.8) that varied in their substrate selectivities and/or wheat xylanase inhibitor sensitivities in dough batter gluten–starch separation of wheat flour showed the importance of these enzyme characteristics for their functionality in this process. A xylanase from Aspergillus aculeatus (XAA) with selectivity for hydrolysis of water extractable arabinoxylan (WE-AX), which is not inhibited by wheat flour xylanase inhibitors decreased batter viscosity and improved gluten agglomeration behaviour. In contrast, a xylanase from Bacillus subtilis (XBS_i) with selectivity for hydrolysis of water unextractable arabinoxylan (WU-AX), which is in vitro inhibited by wheat flour xylanase inhibitors had a negative effect on gluten agglomeration at low enzyme dosages. As expected, solubilisation of WU-AX increased batter viscosities. At higher dosages however, this enzyme also improved gluten agglomeration because of degradation of both WE-AX and enzymically solubilised AX. A mutated B. subtilis xylanase (XBS_ni) with selectivity for hydrolysis of WU-AX comparable to XBS_i but which is not inhibited by wheat flour xylanase inhibitors, increased the level of large gluten aggregates as well as the total gluten protein recovery, even at lower dosages. Because of its inhibitor insensitivity, the solubilisation and degradation of AX proceeded further. An XBS_ni dosage approximately 4 times lower than XBS_i performed as well as its inhibited counterpart. The degradation of both WE-AX and WU-AX by XBS_ni improved the gluten agglomeration behaviour to a larger extent than the XAA treatment which primarily resulted in hydrolysis of WE-AX. The results confirm the detrimental impact not only of WE-AX, but also of WU-AX, on gluten agglomeration in a dough batter gluten–starch separation process. At the same time, they provide firm evidence that xylanases are not only inhibited by xylanase inhibitors in vitro, but are also partly inhibited in the industrial process in which they are used.     

Physico-chemical description of bread dough mixing using two-dimensional near-infrared correlation spectroscopy and moving-window two-dimensional correlation spectroscopy

NIR spectroscopy presents a huge interest in exploring chemical changes during dough mixing. The aim of the present study is to investigate the potential of 2D correlation spectroscopy (2D COS) and moving-window 2D (MW2D) correlation spectroscopy to explore the time dependence of NIR spectral responses during wheat flour dough mixing. NIR spectra were continuously recorded (between 1400 and 2325 nm) during mixing of bread type-dough (based on flour, water and yeast), using an FT-NIR spectrometer with a deported probe. The probe was positioned inside the mixer in contact with the dough. The 2D spectra calculated using raw and second derivative NIR spectra were interpreted in terms of physico-chemical events. Nine different industrial flours were used as raw material to validate the analysis. The results obtained using the 2D COS and the MW2D methods give the possibility to ascribe chemical vibrations (starch, water and gluten) to NIR absorbance changes occurring during dough mixing. The analysis of the NIR spectra identified wavelength shift associated to both dough “free water” and protein secondary structure modifications. During this study, only the MW2D method allowed to identify clearly the time dependence of physico-chemical mechanisms from NIR variation bands.     

Distribution of Water between Wheat Flour Components: A Dynamic Water Vapour Adsorption Study

The water adsorption properties of hard and soft wheat flours and flour components (starch, damaged starch, gluten, soluble pentosans, and insoluble pentosans) were determined at 25 °C using a controlled atmosphere microbalance. At different levels of relative humidity (from 10% to 95%), changes in sample mass (i.e., water gain) were continuously measured versus time and described using exponential models (R²≥0·994). Water adsorption isotherms were constructed for wheat flours and flour components and described using Guggenheim-Anderson-de Boer models (R²≥0·997). It was not possible to distinguish between the selected hard and soft wheat flours by their isotherms. The water-soluble pentosans had the highest water adsorption capacity. The theoretical distribution of water between the flour components (calculated using the Guggenheim-Anderson-de Boer parameters) was starch, 88%; gluten, 10%; and pentosans, 2%.     

A suspension model of the linear viscoelasticity of gluten doughs

We regard gluten dough as a mixture of gluten, starch and water. We show that stress intensification around the starch particles enables one to describe the rapid strain softening of dough at low strains. The starch is in the form of a combination of A-particles (close to oblate spheroids) and B-particles (almost spherical). This suggests that a suspension theory should be able to account for the linear viscoelastic properties of doughs. We develop a new representation for the prediction of the linear viscoelastic properties of a viscoelastic matrix (gluten) with embedded oblate spheroids and spherical particles. The calculations are compared with experiments on gluten mixes derived from an Australian Baker’s flour. We note that the non-sphericity of the A-particles is very important in stiffening the gluten matrix and also that the effective volume fraction of the starch is greater than that calculated by assuming a starch density of 1.4 g/ml.     

Effects of endoxylanases,vital wheat gluten,and gum Arabic on the rheological properties,water mobility,and baking quality of whole-wheat saltine cracker dough

The aim of this study was to improve the baking quality of whole-wheat saltine cracker (WWSC) using endoxylanases, vital wheat gluten (VWG), and gum Arabic. SRC results showed both water-SRC and sucrose-SRC of soft white whole-wheat flour (SWWW) were significantly reduced by gum Arabic (r = 0.94, P < 0.05). Alveograph results indicated that the tenacity and extensibility of the whole-wheat dough (WWD) were increased by VWG. Rheometer G′ and G″ moduli increased with higher addition levels of endoxylanases, VWG, and gum Arabic. Low-field nuclear magnetic resonance (LF-NMR) detected three CPMG proton populations (T₂₁, T₂₂, and T₂₃) in WWD. T₂₁ peak area ratio (tightly bound water) reduced and T₂₂ peak area ratio (less tightly bound water) increased with the levels of each additive. LF-NMR results revealed increased water mobility from T₂₁ population to T₂₂ population with addition of these additives, which was beneficial for gluten to form a continuous network. Both stack height and specific volume of WWSC were improved by the use of endoxylanases, VWG, and gum Arabic, but the breaking strength varied. The results of Orthogonal experimental design showed that the most-improved quality WWSC could be produced by combining 0.035% endoxylanases, 1.5% VWG, and 1.5% gum Arabic into SWWW flour.     

Migration of gluten under shear flow as a novel mechanism for separating wheat flour into gluten and starch

This paper describes a novel principle for the separation of wheat flour into starch and gluten in a concentrated medium. The process is based on the use of simple shear flow in a cone-and-cone device. The separation takes place in two steps. Initially, local segregation of gluten and starch phases occurs, leading to formation of macroscopically visible gluten patches distributed throughout the dough. This local segregation can be understood by considering the dough as a visco-elastic matrix containing an inert filler (starch). Further shearing leads to aggregation of those patches and migration (large-scale separation) towards the apex of the cone. As a result, the wheat dough is separated into a protein-poor fraction, containing less than 4% protein, and a protein-rich fraction containing almost 50% protein on a dry weight basis. However, under the process conditions used, upon a very long shearing, a redistribution of the aggregated gluten structures in the starch phase was observed, demonstrating a processing limit for the separation performance. Compared to traditional processing, the separation process presented shows opportunities for producing high quality gluten accompanied with significant water savings. Considering the fact that simple shear flow in steady rate is less harmful to gluten quality, such a separation process could benefit gluten quality.     

Scanning Electron Microscopic Study of Dough and Chapati from Gluten-reconstituted Good and Poor Quality Flour

Hard and soft wheat flours, which were used in the study, resulted in good and poor quality chapatis respectively. Gluten was isolated and interchanged among the two whole wheat flours and studied by scanning electron microscopy for its influence on structural characteristics of dough and its relation to chapati-making quality. Microscopic observations clearly indicated that larger gluten strands covered starch granules in hard wheat flour dough, while gluten was short and starch granules exposed in dough prepared from soft wheat flour. Greater film forming ability of gluten in hard wheat flour dough manifested in long and bulky starch strands interwoven with protein matrix in its chapati crumb. Higher moisture retention and starch gelatinization as a consequence of greater film forming ability of gluten in hard wheat flour resulted in pliable and soft textured chapati.     

Effects of composition on dough development and air entrainment in doughs made from gluten-starch blends

Gluten and starch are the two main ingredients of a wheat flour dough and it is expected that the extent of air occlusion into the dough would be affected by differences in their relative ratios. The objectives of this paper were to investigate the hydration and development of gluten and how these key events in dough mixing affected air occlusion in gluten-starch doughs. For gluten-starch doughs of the same gluten content, decreasing the water absorption shortened development time and decreased dough density. For formulations of the same water absorption, decreasing the gluten content prolonged the time to development and increased dough density, reflecting less net air entrainment into the dough. The ratios of gluten, starch and water strongly influenced the development of the dough into a good gas-holding material, with the extent of gas entrainment during mixing being evident in measurements of both dough consistency and dough development time.     

燕麦粉对强筋面粉品质特性及其面包品质的影响

面包逐渐成为中国人营养早餐的选择,但面包中膳食纤维含量较低。燕麦是一种食疗兼备的特色杂粮作物,富含膳食纤维。为拓宽燕麦的应用范围、提高面包的营养价值,以优质强筋小麦品种藁优2018和燕麦粉为材料,研究了燕麦粉对小麦面粉面团流变学特性及淀粉糊化特性的影响,并进行了燕麦面包实验室制作和质构分析。结果表明,随着燕麦粉添加比例的增加,面团吸水率逐渐增加,面团稳定时间和粉质质量指数先减小后增加;面团拉伸能量、拉伸长度、拉伸阻力、最大拉伸阻力均逐渐减小。说明燕麦粉对面团拉伸特性各参数均有弱化作用。在藁优2018小麦面粉中添加10%的燕麦粉,既能保证面包的感官品质,又能满足面包营养最大化。     

Effect of glutathione on gelatinization and retrogradation of wheat flour and starch

Reduced glutathione (GSH) commonly exists in wheat flour and has remarkable influence on gluten properties. In this study, effect of GSH on the gelatinization and retrogradation of wheat flour and wheat starch were investigated to better understand the GSH-gluten-starch interactions in wheat flour. Compared with wheat starch, wheat flour showed significant decreases in peak and final viscosity, and gelatinization onset temperature with increasing GSH concentration. GSH depolymerized gluten and thereby broke down the protein barrier around starch granules to make the starch easily gelatinized. However, the interaction between GSH and wheat starch restrained starch swelling. GSH addition resulted in weakened structure with higher water mobility in freshly gelatinized wheat flour dispersions but decreased water mobility in wheat starch dispersions. After storage at 4 °C for 7 d, GSH increased elasticity and retrogradation degree in wheat flour dispersions but retarded retrogradation in wheat starch dispersions. The results indicated that GSH promoted retrogradation of wheat flour, which mainly attributed to the depolymerized gluten embedding in the leached starch chains, and inhibiting the re-association of amylose, and subsequently promoted the starch intermolecular associations and starch retrogradation. This study could provide valuable information for the control of the quality of wheat flour-based products.     

安徽麦区软质小麦籽粒品质和终端制品品质评价

为明确安徽大田生产环境下软质小麦籽粒和终端产品品质表现,评价优质软麦品种的加工适用性,本研究选取该区当前推广种植的24个软质小麦品种,对其籽粒和面粉的主要品质性状及其制品南方馒头和曲奇饼干的品质进行差异性、相关性分析,并以美国软白麦近五年的主要品质性状平均值为理想指标进行灰色关联度比较。结果表明,供试材料的硬度、面粉色泽b^*、湿面筋含量、面团形成时间、稳定时间等籽粒品质性状变异系数较大,而容重、面粉L^*值和吸水率变异系数较小。南方馒头品质性状中,白度差异最小,比容差异最大;曲奇饼干品质性状中,感官评分变异系数较大,饼干直径均值和变异系数都较小。蛋白质含量、湿面筋含量、稳定时间均符合弱筋标准(GB/T 17320-2013)的样品数为0。相关分析表明,容重、降落值、面粉L^*、b^*、白度与大部分性状间相关性不显著;籽粒硬度与水SRC和乳酸SRC均呈显著正相关,与湿面筋含量和面粉a^*值均呈显著负相关。蛋白质含量与面粉a^*值等7个指标均呈显著正相关,与面粉b     

Effect of structured lipid on alveograph characteristics, baking and textural qualities of soft wheat flour

The effect of substituting canola oil/caprylic acid structured lipid (SL) for partially hydrogenated shortening (at 0, 25, 50, 75, and 100% levels) on the rheology of soft wheat flour dough (28.4% total lipid on flour weight basis, 43% moisture) was determined using the Alveograph. The effect of SL substitution on baking and textural qualities of sugar-snap cookies was also investigated. Addition of shortening to soft wheat flour dough resulted in a significant (P<0.05) decrease in dough resistance to deformation (P), dough extensibility (L), and dough baking strength (W), suggesting a less developed gluten network. SL substitution for shortening did not affect P and W. The cookies incorporating SL (50 and 75% SL substitution) were similar (P<0.05) to the shortening control cookies in both baking and textural qualities, but exhibited some baking and textural quality differences at the 25 and 100% SL substitution levels. Correlations (P<0.05) were found between some Alveograph characteristics, and baking and textural qualities.     

郑麦1860品质特性及面条加工适用性分析

为明确郑麦1860的品质及加工适用性,对2020-2021年河南省29个地点收获的郑麦1860的籽粒性状、磨粉品质、面团流变学特性、淀粉糊化特性和面条加工品质指标进行了测定与分析。结果表明,郑麦1860为优质中强筋面条小麦品种,特点是籽粒大、容重高、出粉率高,面条弹性好、色泽白亮、褐变较轻。在不同地点间郑麦1860的多数品质性状变异程度小,品质表现较稳定;相比较而言,其粉质参数、拉伸参数变异程度较大,淀粉糊化特性和面筋特性变异程度次之,籽粒品质性状、磨粉品质和面条加工参数变异程度较小。籽粒硬度、粒径、容重与出粉率呈显著正相关;容重、籽粒蛋白质含量、面粉灰分含量与面条总评分呈显著负相关;面粉色泽L^*值、吸水率、峰值黏度、低谷黏度、终值黏度、回生值与面条总评分呈显著正相关。综上所述,籽粒蛋白质含量、面粉色泽和淀粉糊化特性是影响郑麦1860面条品质的主要因素。郑麦1860制作的面条感官评分高、品质稳定,在豫北、豫东和豫南等区域种植均适合制作优质面条。     

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

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

The role of gluten in a sugar-snap cookie system: A model approach based on gluten–starch blends

The cookie making properties of dough made from blends of commercial wheat starch and gluten were determined. Higher gluten levels decreased dough piece weight, its density, stickiness and hardness. The largest spread was obtained when no gluten was added. However, this resulted in cookies of unacceptable structure. Higher gluten contents increased spread onset time, decreased cookie spread but generally had little impact on set time while additional water lowered spread onset time and likewise had no statistically significant impact on set time. The results showed that the final cookie diameter is quite dependent on the spread onset time which itself depends on the amount of water available to the non-gluten constituents in the system. Size-exclusion high performance liquid chromatography showed that during baking, proteins aggregated. This indicated that during the process the added gluten acquired the necessary mobility for interaction. However, because increasing levels of gluten increasingly decreased the relative level of water available to itself, and because the set time, and, hence, the set temperature, did not depend on the gluten level, we concluded that cookie dough setting was not determined by an ‘apparent’ glass transition. Furthermore, more protein aggregation went hand in hand with less spread.