Influence of wheat starch on rheological,structural and physico-chemical properties gluten–starch dough during mixing

This study mainly explored that the influence of wheat starch source on the rheology behaviours and structural properties of gluten–starch dough, and then the model doughs were prepared by the AK58 wheat gluten and three types of starches from strong (ZM366S), medium (AK58S) and weak gluten wheat (ZM103S) during mixing were studied. The damaged starch content of wheat starch was positively correlated with the wheat gluten strength, while the granule size was negatively. The G', G" and the extension resistance of ZM366S dough were higher than those of other doughs, which implied the source of starch also had a significant influence on the rheological properties. CLSM also observed that ZM366S was more closely bound to the gluten protein network. The glutenin macropolymer (GMP) content of ZM366S model dough was the highest, while the SH content was the lowest. Decreases in elasticity, extension and GMP, and small increase in SH content were displayed during dough mixing. Molecular forces were varied with different wheat starch and mixing time. The covalent bond was the main force between ZM103S and gluten, whereas the hydrogen and covalent bonds were the main force between ZM366S or AK58S and gluten. The interactions between ZM366 starch and gluten were stronger than others starch.     

Effect of inulin on rheological properties of soft and strong wheat dough

The influence of inulin with different degrees of polymerisation (DP) on the farinograph characteristics, extensograph parameters and fermentation rheological properties of soft and strong wheat dough was explored. The results showed that the addition of inulin can reduce the water absorption of doughs, and inulin with lower DP had more significant effect and the influence on the soft dough was stronger than the strong dough. Inulin can enhance mechanical properties of the gluten network and improve the resistance to mixing of soft dough. The extensibility of doughs decreased with increasing inulin. Inulin increased the resistance to extension of soft dough; however, it is reverse for strong dough. Adding inulin significantly increased the volume of gas production and the maximum expansion height of doughs, and the effect of inulin with lower DP was more prominent. Additionally, the gas‐holding capacity of doughs was enhanced by inulin.     

Influence of acidification on dough viscoelasticity of gluten-free rice starch-based dough matrices enriched with exogenous protein

The impact of acid incorporation (acetic + lactic, 0.5%) into rice starch-based doughs enriched with different proteins (egg albumin, calcium caseinate, pea protein and soy protein isolates) at different doses (0, 5 and 10%) has been investigated on dough viscoelastic and pasting profiles. Oscillatory (stress and frequency sweeps) and creep-recovery tests were used to characterize the fundamental viscoelastic behaviour of the doughs, and thermomechanical assays were performed to assess dough viscometric performance. Supplementation of gluten-free doughs with proteins from vegetal sources led to more structured dough matrices (higher viscoelastic moduli and steady viscosities, and lower tan δ, instantaneous and retarded elastic compliances) effect being magnified with protein dose. Acid addition decreased these effects. Incorporation of proteins from animal source resulted in different viscoelastic behaviours according to the protein type, dosage and acidification, especially for casein. Acidification conferred lower dough deformation and notably higher steady viscosity and viscoelastic moduli for 5 %-casein-added dough. Protein-acid interaction favoured higher viscosity profiles, particularly for doughs with proteins of vegetable origin and lower dosage. Dough acidification decreased the pasting temperatures and the amylose retrogradation. Acidification of protein-enriched rice-starch doughs allowed manipulation of its viscometric and rheological properties which is of relevant importance in gluten-free bread development.     

Wheat gluten: high molecular weight glutenin subunits--structure, genetics, and relation to dough elasticity

ABSTRACT:  Gluten proteins, representing the major protein fraction of the starchy endosperm, are predominantly responsible for the unique position of wheat amongst cereals. These form a continuous proteinaceous matrix in the cells of the mature dry grain and form a continuous viscoelastic network during the mixing process of dough development. These viscoelastic properties underline the utilization of wheat to prepare bread and other wheat flour based foodstuffs. One group of gluten proteins is glutenin, which consists of high molecular weight (HMW) and low molecular weight (LMW) subunits. The HMW glutenin subunits (HMW-GS) are particularly important for determining dough elasticity. The common wheat possesses 3 to 5 HMW subunits encoded at the Glu-1 loci on the long arms of group 1 chromosomes (1A, 1B, and 1D). The presence of certain HMW subunits is positively correlated with good bread-making quality. Glutamine-rich repetitive sequences that comprise the central part of the HMW subunits are actually responsible for the elastic properties due to extensive arrays of interchain hydrogen bonds. Genetic engineering can be used to manipulate the amount and composition of the HMW subunits, leading to either increased dough strength or more drastic changes in gluten structure and properties.     

Combined effects of wheat gluten and carboxymethylcellulose on dough rheological behaviours and gluten network of potato–wheat flour-based bread

Incorporating high level of potato flour into wheat flour enhances nutritional values of bread but induces a series of problems that lead to the decline of the bread quality. To overcome the barrier, wheat gluten and carboxymethylcellulose (CMC) were added into potato–wheat composite flour to improve dough machinability and bread quality. The rheological properties, thermo-mechanical properties and microstructures of dough were investigated. The results showed that the interaction between gluten and CMC mitigated the discontinuity of gluten matrix and gluten protein aggregation caused by the addition of potato flour, which yielded a more branched and compact gluten network. The compact three-dimensional viscoelastic structure induced improvements of gas retention capacity and dough stability, making it mimic the machinability properties of wheat flour dough. Bread qualities were apparently improved with the combined use of 4% gluten and 6% CMC, of which specific volume increased by 42.86%, and simultaneously, hardness reduced by 75.93%.     

Influence of water and barley β-glucan addition on wheat dough viscoelasticity

The effects of the addition of two barley β-glucan isolates (0.2–1.0% of wheat flour), differing in molecular weight, and water (53–63% in a poor breadmaking wheat flour, cv. Dion, and 58–68% in a good breadmaking wheat flour, cv. Yekora) on the viscoelastic properties of wheat flour doughs were investigated. A response surface model (CCF) was used to evaluate the effects observed on the dynamic and creep-recovery parameters of the dough. The evaluation was done separately for each combination of β-glucan isolate (BG1 of ～10⁵ Da and BG2 of ～2 × 10⁵ Da) and flour type. Besides the contents of β-glucan and water, the molecular size of the polysaccharide and the flour quality were important determinants of the dough’s viscoelastic behavior. Compared to BG1, the higher molecular weight β-glucan (BG2) brought about major changes on all the rheological responses of the fortified doughs. The addition of appropriate levels of β-glucans and water in the poor breadmaking cultivar (Dion) doughs could yield similar viscoelastic responses to those observed by a non-fortified good breadmaking quality flour dough (Yekora).     

Impact of sourdough, yeast and gluten on small and large deformation rheological profiles of durum wheat bread doughs

The impact of percentage of sourdough (SD) addition and presence of yeast (Y) and/or commercial wheat gluten (G) -added singly and in binary combination- on both small and large deformation rheological performance and viscometric profile of durum wheat bread doughs was considered. Eight distinctive rheological dough features were identified as able/capable to clearly differentiate soured bread doughs made with semolina:remilled semolina rate of 80:20 into defined functional quality groups. The presence of added commercial wheat gluten provided firmer, more elastic and more extensible doughs with slightly lower viscometric profile. Simultaneous presence of yeast/sourdough and yeast/gluten modulate single effects of sourdough on the durum wheat bread dough mechanical properties. Several relationships were found between fundamental and empirical rheological properties and within viscometric features of soured semolina doughs.     

Bread quality of frozen dough substituted with modified tapioca starches

Rheological properties of dough and bread quality of frozen dough-bread containing 18.4% of hydroxypropylated (HTS), acetylated (ATS), and phosphorylated cross-linked (PTS) tapioca starch with different degrees of modification and 1.6% of dried powdered gluten were compared to the same amount of native tapioca starch (NTS) or wheat flour-bread. Doughs substituted with native or modified tapioca starches had the same mixing tolerance as 100% wheat flour. The dough was frozen and stored for 1 week at −18°C, and thawed (one freeze-cycle). The amount of freezable water in the dough substituted with native or modified tapioca starches was not significantly different from that of wheat flour. Frozen dough-bread substituted with highly modified HTS (degree of substitution; DS 0.09–0.11) retarded bread staling, while lowly modified HTS (DS 0.06–0.07) or ATS (DS 0.02–0.04), and PTS (0.004–0.020% phosphoryl content) substitution fastened bread staling as compared with frozen dough-bread baked from wheat flour. The breadcrumbs containing HTS and ATS felt tacky, whereas the bread containing PTS was dry feel. HTS and ATS swelled and collapsed easily during heating, while PTS was difficult to swell and disperse as compared with NTS, therefore the gelatinization properties seemed to affect the texture of bread. Breadcrumb containing HTS showed small firmness during storage, and highly modified HTS-h (DS 0.1) was the smallest. This means highly hydroxypropylated tapioca starch significantly retards bread staling. Staling properties and texture of frozen dough-bread with various tapioca starches were the same as conventional bread baked with the same amount of tapioca starches. These results suggest that a one freeze–thaw cycle and a 1-week frozen period do not change characteristics of starch, gelatinization and retrogradation properties as compared with the conventional method, and the highly modified HTS-h is prominent anti-staling food-stuff in frozen dough.     

The formation and properties of wheat flour doughs

Among the cereal flours, only wheat flour will form a viscoelastic dough when mixed with water. The viscoelasticity appears to be because the gluten proteins are water compatible and thus will swell and interact. The gluten protein's large molecular size and low charge density appear to allow them to interact by both hydrogen and hydrophobic bonds. Wheat flour doughs are also unique in their ability to retain gas. This property appears to result from a slow rate of gas diffusion in the dough. The third major unique property of wheat flour doughs is their ability to set in the oven during baking, and thereby to produce a rigid loaf of bread. Although not clearly understood, this appears to be a heat-induced crosslinking of the gluten proteins.     

Influence of different hydrocolloids on major wheat dough components (gluten and starch)

The aim of this study was to determine the effect of three hydrocolloids from different sources (arabic gum, pectin and hydroxypropylmethylcellulose) on wheat dough major components (gluten and starch) using hydrated model systems. Gluten characteristics were evaluated concerning hydration properties (swelling, water retention capacity, water binding capacity), gluten quality (gluten index, the amount of wet and dry gluten), protein sodium dodecyl sulphate extractability, and rheological properties (elastic and viscous moduli); whereas the effect of hydrocolloids on wheat starch was assessed by recording the viscometric profile. Results showed that hydrocolloids tested affected in different extent to starch and gluten properties, being their effect dependent on the hydrocolloid type and also its concentration. All the hydrocolloids, with the exception of arabic gum, decreased the viscoelastic moduli during heating and cooling, yielding a weakening effect on gluten. Pectin mainly acted on gluten properties, varying gluten hydration, and also the quantity and quality of gluten. In addition, arabic gum acted primarily on the viscometric properties of starch. Therefore, hydrocolloid effect was greatly dependent on the hydrocolloid type, which defines its interaction with other components of the system.     

Ultrasonic Investigation of the Effect of Vegetable Shortening and Mixing Time on the Mechanical Properties of Bread Dough

ABSTRACT:  Mixing is a critical stage in breadmaking since it controls gluten development and nucleation of gas bubbles in the dough. Bubbles affect the rheology of the dough and largely govern the quality of the final product. This study used ultrasound (at a frequency where it is sensitive to the presence of bubbles) to nondestructively examine dough properties as a function of mixing time in doughs prepared from strong red spring wheat flour with various amounts of shortening (0%, 2%, 4%, 8% flour weight basis). The doughs were mixed for various times at atmospheric pressure or under vacuum (to minimize bubble nucleation). Ultrasonic velocity and attenuation (nominally at 50 kHz) were measured in the dough, and dough density was measured independently from specific gravity determinations. Ultrasonic velocity decreased substantially as mixing time increased (and more bubbles were entrained) for all doughs mixed in air; for example, in doughs made without shortening, velocity decreased from 165 to 105 ms⁻¹, although superimposed on this overall decrease was a peak in velocity at optimum mixing time. Changes in attenuation coefficient due to the addition of shortening were evident in both air-mixed and vacuum-mixed doughs, suggesting that ultrasound was sensitive to changes in the properties of the dough matrix during dough development and to plasticization of the gluten polymers by the shortening. Due to its ability to probe the effect of mixing times and ingredients on dough properties, ultrasound has the potential to be deployed as an online quality control tool in the baking industry.     

面团组分及环境因素对面团二硫键形成的影响研究现状

面包、馒头、面条等面制品加工过程的本质是小麦面粉中蛋白与水相互作用形成包裹有淀粉和脂肪的面筋网络结构,该结构加热后转变为形态固定的食品。面团中二硫键的形成量对面筋网络结构的质量和最终食品的品质起着决定性的作用,而面团中的蛋白、淀粉等组分和环境因素影响面团中二硫键的形成量。本文综述了近年来面筋蛋白组成、淀粉组成及种类、面团pH、发酵以及面团成熟温度等环境因素对面团中二硫键形成的影响,提出了未来这方面研究的可能探索方向及相关产业的可能发展趋势,以期为研究人员和食品生产者分析面制品品质变化提供理论支持,促进提高面团品质、面制品质量的二硫键调控理论的形成和创建。     

Promoting dough viscoelastic structure in composite cereal matrices by high hydrostatic pressure

The impact of high hydrostatic pressure (HP) treatment on dough viscoelastic reinforcement of highly-replaced wheat cereal matrices has been investigated. The gelatinisation/pasting and gelling profiles of HP hydrated oat, millet, sorghum and wheat flours, and the small and large deformation rheological parameters of blended wheat/non-wheat doughs were determined. Oat, millet, sorghum and wheat hydrated flours, at dough yield (DY) 160 and 200, were treated for 10 min at 0.1, 200, 350 or 500 MPa. Regardless the nature of the cereal, HP changes flour viscometric features, particularly in softer doughs (DY 200), leading to increased values for viscosity parameters, concerning pasting and paste cooking. Incorporation of 350 MPa pressure-treated flours into bread dough formulation provided increased dynamic moduli values, particularly for wheat and oat/wheat blends, associated to a reinforced dough structure. Highly-replaced composite dough samples treated at 500 MPa proved to be extremely stiff, resistant to stretch, low cohesive and low extensible, and thus not suitable for breadmaking.     

Texture properties of formulated wheat doughs Relationships with dough and bread technological quality

Texture properties of wheat doughs were determined with a texturometer by using texture profile analysis (TPA) as well as Chen and Hoseney methodologies. The time elapsed between two compressions and strain were optimized so that meaningful values were obtained for TPA. Single effects and interactions between flour type, the breadmaking process and anti-staling additives (i.?e. monoglycerides, diacetyl tartaric ester of monoglycerides, sodium stearoyl lactylate, carboxymethylcellulose and hydroxypropylmethylcellulose) on dough texture properties (i.?e. springiness, resilience, hardness, cohesiveness, adhesiveness, chewiness, gumminess and stickiness) were estimated. The breadmaking process and addition of hydrocolloids had the most important effects and interactions on TPA. Hydrocolloids and α-amylase increased dough stickiness. Dough cohesiveness was a good predictive parameter of bread quality. Water content, acidity values and gluten quality were the main factors determining the texture properties of dough.     

Effect of modified whey protein concentrates on empirical and fundamental dynamic mechanical properties of frozen dough

Dairy byproduct proteins are considered natural functional additives having the ability to interact with the starch and gluten network in a dough system and thus behave as dough improvers. Native whey proteins have negative effect in bread making so whey protein concentrates modified to increase viscosity in solution (mWPC) might overcome undesirable weakening of the gluten network which usually occurs in frozen dough products during prolonged times in frozen storage. The objective of this research project was to determine the effect of mWPC on empirical and fundamental dynamic rheological properties of wheat flour dough. The results for empirical rheological studies showed that addition of mWPC had significant effects on mixographic parameters and also increased values of mixing time and peak height percentage. The results for the fundamental mechanical properties of the frozen dough revealed an increase in the values of G′ with the increase in the frequency, along with an upward trend with increasing temperature, but the highest values were obtained after cooling. Addition of mWPC in the dough treatments induced softening in the dough system, as shown by the decrease in the values of the viscoelastic moduli. Rheological and textural changes in the bakery products made from frozen dough could be imparted by the incorporation of modified whey protein concentrates as dough improvers.     

Effect of baked wheat germ on gluten protein network in steamed bread dough

The effect of baked wheat germ (BWG) on the gluten network structure in steam bread dough was investigated. The secondary structure, free sulphydryl (-SH) content, disulphide (-SS-) bonds content and microstructure of gluten were analysed to evaluate gluten structural changes. The addition of different amounts of BWG (0, 2, 4, 6, 8, 10, and 12%) in dough resulted in decreased content of α-helix and β-sheet structures, but increased random coils, which indicated that a disordered structure was formed. The presence of BWG increased the -SH content but decreased the -SS- bonds content, which indicated fracture of disulfide bonds. Confocal laser scanning microscopy (CLSM) analysis indicated that steamed bread dough containing BWG had larger-sized gas cell and granules of starch separated by the protein matrix, which weakened the gluten network structure. These changes may inevitably affect the viscoelastic properties of steamed bread dough.     

Effect of phenolic acids on the rheological properties and proteins of hard wheat flour dough and bread

BACKGROUND: The effects of different phenolic acids on the rheological properties and gluten proteins of hard wheat flour dough and bread were investigated. Caffeic, ferulic, syringic and gallic acids were each blended with hard wheat flour at a concentration of 4.44 µmol L^?1 g^?1 flour. RESULTS: Mixing time and tolerance were reduced with the addition of phenolic acids. The phenolic acids reduced the maximum resistance to extension (R_max) and increased the extensibility of dough, with effects in the following order: gallic < syringic < ferulic < caffeic acid. The effect on R_max was more pronounced in overmixed dough. Loaf volume was most significantly decreased with the addition of caffeic acid. Extraction of sodium dodecyl sulfate‐soluble high‐molecular‐weight proteins was increased in both mixed and fermented doughs by the addition of ferulic and caffeic acids. The order of influence of the phenolic acids on the rheological properties and protein structure of dough and bread was consistent with that of their antioxidant activity. CONCLUSION: The addition of caffeic and ferulic acids reduced R_max and increased the extensibility of hard wheat flour dough by modifying the high‐molecular‐weight gluten, which resulted in decreased bread volume. Copyright © 2011 Society of Chemical Industry     

Scanning electron microscopic observations of dough and bread supplemented with Gastrodia elata Blume powder

Dough and bread prepared from wheat flour containing varying amounts of added Gastrodia elata Blume (GEB) rhizome powder [0, 0.5, 1.0, 1.5, and 2.0% (w/w)] were examined by scanning electron microscopy (SEM) during fermentation and baking. The structure of the doughs containing added GEB was found to be related to the protein matrix. Further, it was found that large starch granules and strings of small starch granules play an important role in dough structure. The control dough (no added GEB) had a membrane-like structure, and doughs with 0.5–1.0% added GEB had membrane-like structures that were more developed than those of the control, resulting in increased bread volumes. At 1.5–2.0% GEB levels, however, the doughs tended to have mesh-like structures and result in decreased bread volumes. The dough samples with 0.5 and 1.0% added GEB powder had well-developed gluten matrices with evenly dispersed starch granules. These samples resulted in breads with numerous gas bubble eruptions on their surfaces and consequently in larger loaf volumes than were obtained at other levels of GEB. After the second fermentation, many expanded starch granules were observed and these starch granules were dispersed more evenly than after the first fermentation. In 0.5–1.0% GEB bread, many of the large starch granules had expanded after fermentation, but small starch granules had not. The data obtained in this study suggest that bread baked with 0.5–1.0% GEB exhibits a better loaf volume due to the more complete development of a gluten matrix.