Genetic Variation in Glutenin Protein Composition of Aestivum and Durum Wheat Cultivars and Its Relationship with Dough Quality

Genetic variability of high molecular weight glutenin subunits and low molecular weight glutenin subunits composition at the Glu-1 loci in Triticum aestivum L., and T. durum L., wheat was studied using sodium dodecyl sulfate polyacrylamide gel electrophoresis and polymerase chain reaction based markers. The end use quality of wheat is mainly influenced by the composition of glutenin protein. Aestivum cultivar GW-273 showed highest gluten index (94.4%) and sedimentation value (61 mL). GW-273 and GW-322 showed highest Glu-1 score of 10 out of 10, indicating superior dough quality for bread making. Results from glutenin protein separation using electrophoresis revealed that selected Indian wheat cultivars were abundant in high molecular weight glutenin subunits AxNull allele, which is responsible for poor quality. Gene specific polymerase chain reaction using high molecular weight glutenin subunits and low molecular weight glutenin subunits primers showed Dx5 and Dy10 in only two cultivars GW-273 and GW-322, which is responsible for good dough quality. Sequencing of high molecular weight glutenin subunits Dx5 gene fragment showed four cysteine at the N-terminal end. Cysteine residues are helpful in intermolecular disulfide bond formation among different glutenin and gliadins proteins leading to good elasticity of dough.     

Glucose oxidase effect on dough rheology and bread quality: A study from macroscopic to molecular level

Enzymes are used in baking to improve dough handling properties and the quality of baked products. Glucose oxidase (GO) is an enzyme with oxidizing effect due to the hydrogen peroxide released from its catalytic reaction. In this study, the macroscopic effect of increasing glucose oxidase concentrations on wheat dough rheology, fresh bread characteristics and its shelf life during storage was determined. A reinforcement or strengthening of wheat dough and an improvement of bread quality can be obtained with the addition of GO, although inverse effects were obtained when excessive enzyme levels were added. The analysis of the gluten proteins at molecular level by high performance capillary electrophoresis and at supramolecular level by cryo-scanning electron microscopy revealed that the GO treatment modified gluten proteins (gliadins and glutenins) through the formation of disulfide and non-disulfide crosslinks. The high molecular weight glutenin subunits showed to be the most susceptible glutenin fraction to the oxidation action of GO. Excessive addition of GO produced an excessive crosslinking in the gluten network, responsible of the negative effect on the breadmaking properties.     

Wheat protein composition and properties of wheat glutenin in relation to breadmaking functionality

The unique breadmaking properties of wheat are generally ascribed to the visco-elastic properties of its gluten proteins. While monomeric gluten proteins (gliadin) show viscous behavior, polymeric gluten proteins (glutenin) are elastic. The unique elasticity of glutenin results to a large extent from its polymeric nature. Glutenin is a highly heterogeneous mixture of polymers consisting of a number of different high- and low-molecular-weight glutenin subunits linked by disulfide bonds. Although glutenin obviously is the major polymeric protein in wheat, other polymeric proteins occur as well. Their importance in breadmaking may be underestimated. Nevertheless, variations in both quantity and quality of glutenin strongly determine variations in breadmaking performance. Structural features of different classes of glutenin subunits are described. Variations in glutenin quality may result from variations in its (1) structure, (2) size distribution, and (3) subunit composition. Some hypotheses on glutenin structure and current insights into the role of glutenin size distribution are evaluated. Finally, different ways in which variation in glutenin composition may directly or indirectly (by affecting glutenin structure and/or size distribution) influence glutenin quality are discussed.     

Rebuilding gluten network of damaged wheat by means of glucose oxidase treatment

The disrupted gluten structure of infested wheat flours leads to low‐quality doughs unusable in bread‐making processes. Enzymes are replacing chemical treatments in the food industry as a tool to treat weak flours. Glucose oxidase is one of the most promising oxidative enzymes, although its efficiency compared with the alcohol‐soluble fraction of gluten proteins has not yet been demonstrated. If this enzyme could restore the broken covalent bonds between glutenin subunits, the gluten network of damaged wheat flour would recover its native structure and functionality. This treatment would allow bakers to use damaged flour, reducing the economic losses caused by this plague around Europe and North Africa. Electrophoretic studies demonstrated the formation of high‐molecular‐weight aggregates in the glutenin fraction, which had a characteristic thermal stability depending on enzyme dosage. Those molecular studies agreed with the bread‐making assays made with maximum enzyme dosage and microstructure determination. Overall results showed that glucose oxidase is a real alternative to traditionally used chemical oxidants. It acted specifically on the high‐molecular‐weight glutenin subunits of damaged wheat, forming dityrosine crosslinks between the wheat proteins, which reinforced the gluten network and gave away the dough functionality. Copyright © 2007 Society of Chemical Industry     

Dispersion in the Presence of Acetic Acid or Ammonia Confers Gliadin‐Like Characteristics to the Glutenin in Wheat Gluten

Spray‐dried gluten has unique properties and is commercially available in the food industry worldwide. In this study, we examined the viscoelastic properties of gluten powder prepared by dispersion in the presence of acetic acid or an ammonia solvent and then followed by lyophilization instead of a spray drying. Mixograph measurements showed that the acid‐ and ammonia‐treated gluten powders had marked decreases in the time to peak dough resistance when compared with the control gluten powder. The integrals of the dough resistance and bandwidth for 3 min after peak dough resistance decreased in both treated gluten powders. Similar phenomena were observed when gliadin was supplemented to gluten powders. Basic and acidic conditions were applied to the acid‐ and ammonia‐treated gluten powders, respectively, and the viscoelastic behaviors were found to depend on the pH in the gluten dispersion just before lyophilization. These behaviors suggest that gluten may assume a reversible change in viscoelasticity by a fluctuation in pH during gluten dispersion. SDS‐PAGE showed that the extractable proteins substantially increased in some polymeric glutenins including the low molecular weight‐glutenin subunit (LMW‐GS) when the ammonia‐treated gluten powder was extracted with 70% ethanol. In contrast, the extractable proteins markedly increased in many polymeric glutenins including the high molecular weight‐glutenin subunit and/or the LMW‐GS when the acid‐treated gluten powder was extracted with 70% ethanol. It thus follows that the extractability of polymeric glutenin to ethanol increases similarly to gliadin when gluten is exposed to an acidic or a basic pH condition; therefore, glutenin adopts gliadin‐like characteristics.     

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.     

Biotechnology of Wheat Quality

Wheat gluten proteins are largely responsible for the visco-elastic properties that allow doughs to be processed into bread and various other food products including cakes, biscuits (cookies), pasta and noodles. Detailed biochemical and biophysical studies are revealing details of the molecular structures and interactions of the individual gluten proteins, and their roles in determining the functional properties of gluten. In particular, one group of gluten proteins, the high molecular weight (HMW) subunits of glutenin, have been studied in detail because of their role in determining the strength (elasticity) of doughs. The development of robust transformation systems for bread wheat is now allowing the role of the HMW subunits to be explored experimentally, by manipulating their amount and composition in transgenic plants. Such studies should lead to improvement of the processing properties of wheat for traditional end uses and the development of novel end uses in food processing or as raw material for other industries. © 1997 SCI.     

The influence of nitrogen fertilisation on quantities and proportions of different protein types in wheat flour

The flours of 13 wheat varieties grown at different levels of nitrogen fertilisation were characterised by the quantitative determination of flour protein groups and gluten protein types using a combined extraction/HPLC procedure. The results demonstrate that the quantities of albumins and globulins were scarcely influenced by different nitrogen fertilisation, whereas those of gluten proteins (gliadins, glutenins) were strongly influenced. The effect on gliadins was more pronounced than on glutenins, as well as the effect on major protein types (α-gliadins, γ-gliadins, LMW subunits of glutenin) in comparison with minor types (ω-gliadins, HMW subunits of glutenin). The proportions of hydrophilic proteins (ω-gliadins, HMW subunits of glutenin) were increased by high levels of nitrogen and those of hydrophobic proteins (γ-gliadin, LMW subunits of glutenin) were decreased. The degree of the effects on both quantities and proportions of flour protein groups and gluten protein types was strongly dependent on the variety. © 1998 SCI.     

Application of Capillary Electrophoresis to Determine the Technological Properties of Wheat Flours by a Glutenin Index

ABSTRACT:  Capillary electrophoresis was used to characterize glutenin proteins from ancient varieties of Southern Italy common wheat and to determine the technological properties of wheat flours based on a glutenin index. Three zones were identified in the electropherograms, indicated as A, B, and C according to electroelution order. The three zones corresponded to the low molecular weight glutenin subunits and to the y- and x-type high molecular weight subunits, respectively. The ratio B/C was correlated to the alveographic parameter P/L. These results indicated that flours resulting in a B/C ratio lower than 2 produced elastic doughs whereas flours resulting in a B/C ratio higher than 2 produced doughs more resistant to extension. This study showed that capillary electrophoresis is useful for determining the types and quantities of gluten proteins in the evaluation of wheat-flour technological properties of a limited number of noncommercial varieties as evidenced by the x-type content which seems to strongly influence the flour technological parameters.     

Comparative proteome analysis of glutenin synthesis and accumulation in developing grains between superior and poor quality bread wheat cultivars

BACKGROUND: Wheat glutenins are the major determinants of wheat quality. In this study, grains at the development stage from three wheat cultivars (Jimai 20, Jin 411 and Zhoumai 16) with different bread‐making quality were harvested based on thermal times from 150 °C_d to 750 °C_d, and were used to investigate glutenin accumulation patterns and their relationships with wheat quality. RESULTS: High and low molecular weight glutenin subunits (HMW‐GSs and LMW‐GSs) were synthesised concurrently. No obvious correlations between HMW/LMW glutenin ratios and dough property were observed. Accumulation levels of HMW‐GSs and LMW‐GSs as well as 1Bx13 + 1By16 and 1Dx4 + 1Dy12 subunits were higher in superior gluten quality cultivar Jimain 20 than in poor quality cultivar Jing 411 and Zhoumai 16. According to the results of two‐dimensional gel electrophoresis, six types of accumulation patterns in LMW‐GSs were identified and classified. The possible relationships between individual LMW‐GSs and gluten quality were established. CONCLUSION: The high accumulation level of HMW‐GSs and LMW‐GSs as well as 1Bx13 + 1By16 and 1Dx4 + 1Dy12 subunits contributed to the superior gluten quality of Jimai 20. Two highly expressed and 16 specifically expressed LMW glutenin subunits in Jimain 20 had positive effects on dough quality, while 17 specifically expressed subunits in Zhoumai 16 and Jing 411 appeared to have negative effects on gluten quality. Copyright © 2011 Society of Chemical Industry     

Developmental changes in storage proteins and peptidyl prolyl cis–trans isomerase activity in grains of different wheat cultivars

In the present study, storage proteins from five different wheat cultivars were extracted, fractionated and evaluated for their accumulation at different stages of development. SDS–PAGE analysis revealed that the accumulation of high molecular weight glutenin subunits was cultivar and stage dependent. However, low molecular weight glutenin subunits’ accumulation was not altered significantly after 16 days post anthesis in any of the cultivars. The rheological parameters (storage- and loss-modulus) of dough and gluten showed close association with either gliadins or glutenins. Peptidyl prolyl cis–trans isomerase (PPIase) activity, measured at different stages of grains development, showed variability with both the developmental stage and cultivar, and appeared to be primarily due to cyclophilins. Principal component analysis revealed the association of PPIase activity with either gliadin or total proteins, suggesting their significant role in the deposition of storage proteins in wheat.     

Relationship between gluten degradation by Aelia spp and Eurygaster spp and protein structure

Gluten from wheat damaged by heteropterous insects loses its functionality after a short period of resting. In this study the properties of the gluten from damaged wheat are compared with that from sound wheat in order to understand the changes produced during incubation at 37 °C. The amounts of free thiol and amino groups were quantified, obtaining a marked increase of those groups during incubation of the damaged wheat. The thermal characterization of the damaged gluten showed a decrease in the denaturation temperature and a pronounced increase in the protein denaturation enthalpy after a short incubation, although the value of that enthalpy greatly dropped with a longer incubation period. The high‐molecular‐weight glutenin subunits (HMW‐GS) were rapidly hydrolysed while the low‐molecular‐weight glutenin subunits (LMW‐GS) showed a slower degradation. It seems that the HMW‐GS backbone was first hydrolysed, leading to a protein structure with higher thermal stability but, as the hydrolysis proceeded, a deeper degradation of the structure yielded a protein structure with lower denaturation enthalpy. The loss of gluten functionality results from complex changes in the gluten structure at the first and second level of the protein organization structure. Copyright © 2005 Society of Chemical Industry     

面粉特性对燕麦挂面品质的影响

为了探究面粉特性对燕麦挂面品质的影响,测定了7种小麦粉的粉质特性、拉伸特性、麦谷蛋白大聚体(GMP)干质量、面筋蛋白及其亚基组成,用其制作燕麦挂面,并通过相关性分析研究面粉特性对燕麦挂面品质的影响.结果表明,面粉的吸水率与燕麦挂面的硬度、适口性、韧性和感官总分呈正相关;拉伸能量、延伸度、最大拉伸阻力与燕麦挂面的拉断距离...     

Protein–lipid interactions in gluten elucidated using acetic acid fractionation

Protein–lipid interactions in dough have an important impact on the quality of bakery products. Understanding of protein–lipid interactions in gluten can enhance the development of technological solutions to improve the breadmaking quality of flour as well as the functional properties of gluten. In this study, acetic acid at two different concentrations was used for treating and fractionating gluten. The impact of these procedures on the distribution of lipid components was measured. Acetic acid was able to dissociate non-polar lipids from the gluten protein matrix. Upon fractionation monomeric proteins (predominantly gliadins) and phospholipids were high in the 0.01 M acetic acid soluble fraction. The subsequent fractionation step using 0.1 M acetic acid resulted in an increased amount of high-molecular-weight glutenin subunits (HMW-GS) in the soluble fraction, along with more non-polar lipids and glycolipids in both the free and bound lipid extracts. The distribution of lipid classes demonstrates that non-polar lipids are either associated with the glutenin polymeric network through hydrophobic interactions or entrapped within the gluten matrix. The results also indicate that in gluten, glycolipids are likely to be associated with glutenins through both hydrophobic interactions and hydrogen bonds whilst phospholipids preferentially interact with gliadins and lipid binding proteins.     

The role of a low molecular weight glutenin fraction in the cooking quality of durum wheat pasta

Durum wheat glutenin fractions, composed of two low molecular weight proteins DSG-1 and DSG-2 (durum wheat (Triticum durum Desf) sulphurrich glutenin fractions) were extracted from semolina samples using a low concentration of Na tetradecanoate after extracting albumins, globulins and gliadins. DSG proteins have a high? SH plus S? S content. A highly significant correlation was found between the ? SH plus S? S content of this DSG-rich fraction and the cooking quality of pasta (0.63, P <0.01 with firmness and 0.86, P <0.001 with the state of the surface of the cooked pasta) and this seems to be a functional relationship. The use of acetic acid at various molarities showed the presence of high molecular weight glutenin fractions with differing solubility properties. In this respect, differences were found between varieties which are placed in the same group according to the classification of durum wheats based upon the composition of high molecular weight glutenin subunits.     

Aggregative and structural properties of wheat gluten during post-harvest maturation

Wheat post-harvest maturation induced baking and technological quality improvement through a series of biochemical and colloidal changes. Weak-, middle-, and strong-gluten wheat displayed varying gluten network structures that determined the flour ingredient formulations and processing conditions. However, the aggregation and structural properties of wheat with different gluten strengths post-harvest remain largely unexplored. In this study, we investigated changes in the aggregative properties of gluten protein, gluten composition, S–S content, network structure, and secondary structures of weak-, middle-, and strong-gluten wheat during post-harvest maturation. The results indicated that the macromolecular aggregation of gluten proteins was impaired in weak-gluten wheat, while it was enhanced for middle- and strong-gluten wheat during storage. Post-harvest maturation resulted in an increase in glutenin content and a decline in the gliadin and gliadin/glutenin ratio in middle- and strong-gluten wheat as well as a decreased glutenin content in weak-gluten wheat. Moreover, additional gluten subunits were observed in middle- and strong-gluten wheat, but no substantial change was observed in weak-gluten wheat with long storage times. The disulfide bond content of gluten protein for middle-gluten and strong-gluten gradually increased but declined for weak-gluten wheat. Secondary structure analysis of gluten indicated that post-harvest maturation caused the conversion of α-helix to random coil for weak-gluten wheat, β-turn and random coil to α-helix for middle-gluten wheat, and β-turns to α-helix for strong-gluten wheat, which led to a disordered structure for weak gluten and an ordered stable gluten network for middle- and strong-gluten. Thus, the increased S–S and α-helix content induced by post-harvest maturation enhanced the aggregation of gluten proteins for middle- and strong-gluten wheat, resulting in a denser network structure. Conversely, the decrease in the content of α-helix resulted in the existence of a looser gluten network structure for weak-gluten wheat during post-harvest maturation.     

Wheat-bug damage in New Zealand wheats. Development of a simple SDS-sedimentation test for bug damage

Lines of three varieties of New Zealand wheat (cv. Aotea, Oroua and Kopara) damaged by wheat-bug were investigated. Hydrolysis of gluten proteins was shown to be of the endo- rather than the exo-proteolytic type. Electrophoresis revealed that the bug protease had a high specificity for the high molecular weight (HMW) glutenin subunits. An autolytic assay method was developed based on the decrease in sodium dodecyl sulphate (SDS)-sedimentation volume for bug-damaged flours when they were incubated in distilled water for 30 min at 37°C. This method was specific for bug damage and exhibited no interference from other grain defects such as heat damage, field sprouting and laboratory germination.     

Studies on the distribution and binding of endogenous glutathione in wheat dough and gluten. II. Binding sites of endogenous glutathione in glutenins

For the identification of the binding sites of glutathione (GS) in glutenins, flour of the wheat cultivar " Canadian Western Red Spring " was mixed with water containing ³⁵S-labelled reduced GS as a tracer. The resulting dough was washed in a Glutomatic, and, in order to remove gliadins, the gluten obtained was extracted with 70% aqueous ethanol adjusted to pH 5.5 with acetic acid. The residual proteins (glutenins) were hydrolyzed with thermolysin, and the hydrolysate was separated by gel permeation chromatography on Sephadex G25 and by several steps of reversed-phase HPLC on C₁₈ silica gel. The major radioactive disulphide peptides identified by scintillation analysis were collected and analysed for their amino acid sequences. Twenty-five peptides linked to GS could be assigned to known sequences of gluten proteins. Most peptides (16) were derived from low molecular weight (LMW) subunits of glutenin. Among these, 13 peptides contained the cysteine residue C^b*, which is present in the repetitive sequence region of LMW subunits and which has been postulated to form intermolecular disulphide bonds. This peptide type represented 45% of the total radioactivity of isolated peptides. Three further peptides from LMW subunits representing 46% of radioactivity included cysteine C^x, which has also been proposed to form intermolecular disulphide bonds. Four peptides with 3.2% of radioactivity could be assigned to high molecular weight subunits (cysteines C^b, C^d, C^e, C^y) and four peptides (3.0% of radioactivity) to glutenin-bound %-gliadins (C^b*, C^w, C^z). One peptide (3.3% of radioactivity) corresponded to cysteine C^c from %-gliadins or LMW subunits. Altogether the cysteine residues in glutenins, which are usually linked by intermolecular disulphide bonds, contributed up to 95% of total radioactivity. The results obtained are in accordance with the effect of reduced GS on the rheological properties of dough, namely the weakening of dough by depolymerization of glutenin polymers via specific cleavage of intermolecular disulphide bonds.     

小麦谷蛋白亚基的组成及含量与谷蛋白聚合体大分子的关系及其对面包烘焙品质的影响

含有高分子量谷蛋白亚基(HMW-GS)5 10的生物型小麦与2 12的生物型小麦相比，前者谷蛋白具有更大的分子量分布。高低分子量谷蛋白亚基的比例对于谷蛋白聚合体分子量的大小起着重要的作用，谷蛋白聚合体的体积越大，含有的高低分子量谷蛋白亚基的比例越高。SDS非可溶性谷蛋白含有较高比例的高低分子量谷蛋白亚基，并且其分子量要比可溶性谷蛋白聚合体的大。谷蛋白聚合体分子量分布的差异是不同小麦品种面包烘焙品质存在差异的重要因素。     

Role of gluten and its components in influencing durum wheat dough properties and spaghetti cooking quality

Protein is an important component of grain which affects the technological properties of durum wheat. It is known that the amount and composition of protein can influence dough rheology and pasta quality but the influence of the major classes of protein is not well documented. The influence of the various gluten components on dough and pasta properties was investigated. The protein composition of durum semolina was altered by either adding gluten fractions to a base semolina or preparing reconstituted flours with varying protein composition. The effects on semolina dough rheology and spaghetti texture were measured. Published methods to isolate relatively pure quantities (gram amounts) of glutenin, gliadin, high molecular and low molecular weight glutenin subunits were evaluated and modified procedures were adopted. Reconstituted flours with additional glutenin increased dough strength while additional gliadin and LMW‐GS decreased strength. These changes did not impact on spaghetti texture. Results from using the addition of protein fractions to a base semolina showed that gluten and glutenin addition increased the dough strength of a weak base semolina while gliadin addition weakened the base dough further. Addition of HMW‐GS greatly increased dough strength of the base while addition of LMW‐GS greatly reduced dough strength. Again, these affects were not translated into firmer pasta. Copyright © 2007 Society of Chemical Industry