Glutenin Polymers Research Articles

Spontaneous gelation of wheat gluten proteins in a food grade solvent

Structuring wheat gluten proteins into gels with tunable mechanical properties would provide more versatility for the production of plant protein-rich food products. Gluten, a strongly elastic protein material insoluble in water, is hardly processable. We use a novel fractionation procedure allowing the isolation from gluten of a water/ethanol soluble protein blend, enriched in glutenin polymers at an unprecedented high ratio (50%). We investigate here the viscoelasticity of suspensions of the protein blend in a water/ethanol (50/50 v/v) solvent, and show that, over a wide range of concentrations, they undergo a spontaneous gelation driven by hydrogen bonding. We successfully rationalize our data using percolation models and relate the viscoelasticity of the gels to their fractal dimension measured by scattering techniques. The gluten gels display self-healing properties and their elastic plateaus cover several decades, from 0.01 to 10,000 Pa. In particular very soft gels as compared to standard hydrated gluten can be produced.

Influence of temperature on the composition and polymerization of gluten proteins during grain filling in spring wheat (Triticum aestivum L.)

One Norwegian and one UK spring wheat cultivar, Bjarne and Cadenza, respectively, were grown in climate chambers to investigate the effects of lower to moderate temperatures during grain filling on the gluten quality. Two experiments were carried out with weekly fertilization until anthesis, while post-anthesis fertilization was applied in a third experiment.The proportions of different gluten proteins were affected by temperature in a similar manner for both cultivars when grown without post-anthesis fertilization. However, whereas low temperature strongly decreased %UPP for Cadenza, Bjarne had high %UPP at all temperature regimes. The results indicated that the assembly of glutenin polymers in Bjarne was less sensitive to variation in temperature than in Cadenza. Thus, our results suggested that the temperature influenced the proportion of different gluten proteins in both cultivars, while its effects on the assembly of the glutenin polymers were cultivar dependent.The duration of grain filling was longer at the lower temperatures, and this was associated with increased grain weight. Temperature had little effect on the amount of protein accumulated per grain, thus the proportion of proteins was strongly decreased at lower temperatures. This was to some extent, but not fully counteracted by post-anthesis fertilization.

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.

Grain filling duration and glutenin polymerization under variable nitrogen supply and environmental conditions for durum wheat

The end-use value of durum wheat (Triticum turgidum L. subsp. durum (Desf.) Husn.) is mainly governed by its grain protein concentration and composition. Adjustment of variables to compensate for inter-annual and location variations in semolina quality leads to high cost for processors in the wheat industry. A better understanding of the mechanisms governing environmental variations of grain protein composition is thus required. Here, a field experiment was setup in a Mediterranean environment with the aim to analyze the effect of sowing date and nitrogen (N) fertilization on the dynamics of grain dry mass, water, protein composition and glutenin polymer size distribution for durum wheat cv. Creso. The results indicated that (1) grain dry mass accumulation was related to grain water concentration and stopped at 44.9% independently of the growing conditions and N supply; (2) during the grain filling period as well as at ripeness maturity, the quantity of the different protein fractions scaled with the quantity of N per grain; (3) SDS-extractable glutenin polymers were produced continuously until the same grain water concentration as the dry mass deposition was reached; (4) SDS-unextractable polymeric proteins were found as early as 7 days after anthesis and their rate of accumulation increased sharply when grain dry mass was 60% of its final value and proceeded at a constant rate until ripeness maturity, thus suggesting that the insolubilization of glutenin polymers is not directly related to the rapid loss of water after physiological maturity, but rather to the continuous dehydration of the grain.

Fabrication and characterization of carboxylated cellulose nanocrystals reinforced glutenin nanocomposite

The non-biodegradable and non-renewable nature of plastic packaging has led to increasing interest in packaging materials based on bio-nanocomposites (biopolymer matrix reinforced with nanofillers). One such material is wheat gluten and its components. In this study we investigated nanocomposite materials prepared by casting a mixture of extracted glutenin from wheat gluten as the matrix and different concentrations of 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-carboxylated cellulose nanocrystals (C-CNC) as the reinforcing agent. The resulting films were characterized for their thermomechanical and barrier properties. Scanning electron microscopy (SEM) observations confirmed that the filler was homogeneously distributed in the matrix at the low and medium loadings, but some agglomerates and voids were visible at concentrations > 5 wt%. The mechanical properties showed that the presence of C-CNC (5 wt%) resulted in an increase (58.8 %) in tensile strength (TS) of glutenin films while at higher contents, the TS tended to decrease because of partial agglomeration of the filler. These effects were also reflected in the dynamic mechanical analysis (DMA) results and at a 5 wt% loading of nanocrystals the glutenin film gave the highest storage modulus (E′). The results obtained from differential scanning calorimetry (DSC) curves indicated that increasing the amount of C-CNC from 0 to 10 wt% led to an increase in glass transition temperature (Tg) from −29.8 to −23.7 °C. Although the use of C-CNC reduced the resistance to water vapor permeability (WVP) and water absorbance (WA), its incorporation up to 5 wt% resulted in composites with the lowest weight loss in water (WL). These results demonstrated that nanocellulose can reinforce glutenin polymers and that this system has potential as a packaging material, although much further study is needed.

Effects of genotype, season, and nitrogen nutrition on gene expression and protein accumulation in wheat grain.

Six commercial U.K. cultivars of winter wheat selected to represent different abilities to partition nitrogen into grain protein were grown in replicated field trials at five different sites over three seasons. The proportion of LMW glutenin subunits decreased and the proportion of gliadins increased during grain development and in response to N application. Differences were observed between the proportions of LMW glutenin subunits and gliadins in low- and high-protein grain, these two fractions being decreased and increased, respectively. There was little effect of grain protein content on the proportions of either the HMW glutenin subunits or large glutenin polymers, which are enriched in these subunits, with the latter increasing during development in all cultivars. The proportion of total protein present in polymers in the mature grain decreased with increasing N level. Correlations were also observed between the abundances of gliadin protein transcripts and the corresponding proteins.

The effect of sodium chloride on gluten network formation and rheology

Gluten samples were obtained from two wheat flours with different levels of total protein in the presence or absence of sodium chloride (2% flour base). The dynamic oscillation rheology, large extensional deformation, confocal laser scanning microscopy (CLSM), transmission electron microscopy (TEM) and chemical analysis of disulfide bond linkages and the ratio of polymeric glutenins and monomeric gliadins were used to investigate the effect of salt on the structure and rheological properties of gluten. CLSM and TEM images showed that NaCl caused the gluten to form fibrous structure. The presence of NaCl increased non-covalent interactions and β-sheet structure, measured by FTIR, in gluten proteins. The gluten matrix formed with salt resulted in higher tan δ values corresponding to a less elastic network when measured using oscillatory rheometry. Large deformation extensional measurements showed that the maximum force to fracture were lower for the gluten samples prepared in the presence of NaCl. The results from this study indicate that changes in the solvent quality due to the presence of NaCl during dough mixing result in different molecular conformation and network structure of gluten proteins which contributed to the differences in the rheological properties.

An asparagine residue at the N-terminus affects the maturation process of low molecular weight glutenin subunits of wheat endosperm

BackgroundWheat glutenin polymers are made up of two main subunit types, the high- (HMW-GS) and low- (LMW-GS) molecular weight subunits. These latter are represented by heterogeneous proteins. The most common, based on the first amino acid of the mature sequence, are known as LMW-m and LMW-s types. The mature sequences differ as a consequence of three extra amino acids (MET-) at the N-terminus of LMW-m types. The nucleotide sequences of their encoding genes are, however, nearly identical, so that the relationship between gene and protein sequences is difficult to ascertain.It has been hypothesized that the presence of an asparagine residue in position 23 of the complete coding sequence for the LMW-s type might account for the observed three-residue shortened sequence, as a consequence of cleavage at the asparagine by an asparaginyl endopeptidase.ResultsWe performed site-directed mutagenesis of a LMW-s gene to replace asparagine at position 23 with threonine and thus convert it to a candidate LMW-m type gene. Similarly, a candidate LMW-m type gene was mutated at position 23 to replace threonine with asparagine. Next, we produced transgenic durum wheat (cultivar Svevo) lines by introducing the mutated versions of the LMW-m and LMW-s genes, along with the wild type counterpart of the LMW-m gene.Proteomic comparisons between the transgenic and null segregant plants enabled identification of transgenic proteins by mass spectrometry analyses and Edman N-terminal sequencing.ConclusionsOur results show that the formation of LMW-s type relies on the presence of an asparagine residue close to the N-terminus generated by signal peptide cleavage, and that LMW-GS can be quantitatively processed most likely by vacuolar asparaginyl endoproteases, suggesting that those accumulated in the vacuole are not sequestered into stable aggregates that would hinder the action of proteolytic enzymes. Rather, whatever is the mechanism of glutenin polymer transport to the vacuole, the proteins remain available for proteolytic processing, and can be converted to the mature form by the removal of a short N-terminal sequence.

Protein composition of wheat gluten polymer fractions determined by quantitative two-dimensional gel electrophoresis and tandem mass spectrometry

BackgroundCertain wheat gluten proteins form large protein polymers that are extractable in 0.5% SDS only after sonication. Although there is a strong relationship between the amounts of these polymers in the flour and bread-making quality, the protein components of these polymers have not been thoroughly investigated.ResultsFlour proteins from the US bread wheat Butte 86 were extracted in 0.5% SDS using a two-step procedure with and without sonication. Proteins were further separated by size exclusion chromatography (SEC) into monomeric and polymeric fractions and analyzed by quantitative two-dimensional gel electrophoresis (2-DE). When proteins in select 2-DE spots were identified by tandem mass spectrometry (MS/MS), overlapping spots from the different protein fractions often yielded different identifications. Most high-molecular-weight glutenin subunits (HMW-GS) and low-molecular-weight glutenin subunits (LMW-GS) partitioned into the polymer fractions, while most gliadins were found in the monomer fractions. The exceptions were alpha, gamma and omega gliadins containing odd numbers of cysteine residues. These proteins were detected in all fractions, but comprised the largest proportion of the SDS-extractable polymer fraction. Several types of non-gluten proteins also were found in the polymer fractions, including serpins, triticins and globulins. All three types were found in the largest proportions in the SDS-extractable polymer fraction.ConclusionsThis is the first study to report the accumulation of gliadins containing odd numbers of cysteine residues in the SDS-extractable glutenin polymer fraction, supporting the hypothesis that these gliadins serve as chain terminators of the polymer chains. These data make it possible to formulate hypotheses about how protein composition influences polymer size and structure and provide a foundation for future experiments aimed at determining how environment affects glutenin polymer distribution. In addition, the analysis revealed additional layers of complexity to the wheat flour proteome that should be considered when evaluating quantitative 2-DE data.

A MALDI-TOF based study of the in-vivo assembly of glutenin polymers of durum wheat

Wheat grain is recognized as the most suitable raw material for bread and pasta making due to the unique viscoelasticity of its storage proteins, and in particular its glutenin polymers. During grain development, low molecular weight (LMW) and high molecular weight (HMW) glutenin subunits (GS) gradually assembled through inter-chain disulfide bonds. Despite the impact of the final glutenin polymer size distribution on wheat technological quality, little is known concerning the oxidative folding of GS. In particular, which of their cysteine (Cys) residues participate to GS inter-chains remains putative. In this study GS from immature Triticum durum wheat grain were separated (1D SDS-PAGE) and digested into peptides, which were analyzed by MALDI-TOF/TOF. Differential alkylation of free and disulfide bonded Cys allowed us to identify the oxidative folding state of five types of LMW-GS and of the 1Bx20 HMW-GS. GS as monomers or as part of small oligomers carried a high number of free cysteine residues. In addition, some Cys residues, hitherto assumed as involved in intra-chain disulfide bonds, appeared simultaneously in free and oxidized forms. The last result could be assigned to their partial-blocking by glutathione. We concluded that the complete oxidative folding of LMW-GS is a late event, subsequent to GS inter-chain pairing.

Composition of gluten proteins in spring and winter wheat grain cultivated under conditions of varied fertilization

The composition of protein fractions, particularly gluten protein, determines the nutritional values and baking properties of wheat grain. The baking characteristics of grain are strongly related to the quantity of monomeric gliadins and polymeric glutenins. Their accumulation and proportions impact the viscosity, porosity, and degree of rising in baking. These properties determine the applications of wheat in the baking industry. The changes in protein composition are mainly influenced by the genotype, the environment, and the interactions between the genotype and the environment and fertilization. The presented results of the studies refer to the impact of fertilization using waste products (meat bone meals, MBMs) originating from the recycling industry, in comparison to organic and mineral fertilizers, on the technological quality of spring and winter wheat based on the proportion of gluten proteins. The content of gluten proteins, particularly high molecular weight (HMW) and low molecular weight glutenins, in the protein of the examined spring and winter wheat cultivars increased with manure and bone meat meal fertilization, both with and without the addition of effective microorganisms. The grain of the Tybalt spring wheat cultivar had a low content of the harmful α/β-gliadin subunits in relation to the examined wheat cultivars under the influence of fertilization. Fertilization with compost generated a beneficial ratio of the most desired HMW glutenins to the total content of gluten proteins in spring wheat. The evaluated fertilizers (MBM, organic fertilizers) and the addition of microbiological preparations to MBM have good fertilizing properties by making the soil nutrients available to plants.

Transformation of common wheat (Triticum aestivum L.) with avenin-like b gene improves flour mixing properties.

Avenin-like b proteins may contribute to the viscoelastic properties of wheat dough via inter-chain disulphide bonds, due to their rich cysteine residues. In order to clarify the effect of the avenin-like b proteins on the functional properties of wheat flour, the functional and biochemical properties of wheat flour were analyzed in three transgenic wheat lines overexpressing the avenin-like b gene using the sodium dodecyl sulfate sedimentation (SDSS) test, Mixograph and size exclusion-high performance liquid chromatography (SE-HPLC) analysis. The results of the SDSS test and Mixograph analysis demonstrated that the overexpression of avenin-like b proteins in transgenic lines led to significantly increased SDSS volume and improved flour mixing properties. The results of SE-HPLC analysis of the gluten proteins in wheat flour demonstrated that the improvement in transgenic line flour properties was associated with the increased proportion of large polymeric proteins due to the incorporation of overexpressed avenin-like b proteins into the glutenin polymers. These results could help to understand the influence and mechanism of avenin-like b proteins on the functional properties of wheat flour.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-013-9913-1) contains supplementary material, which is available to authorized users.

Overexpression of avenin-like b proteins in bread wheat (Triticum aestivum L.) improves dough mixing properties by their incorporation into glutenin polymers.

Avenin-like b proteins are a small family of wheat storage proteins, each containing 18 or 19 cysteine residues. The role of these proteins, with high numbers of cysteine residues, in determining the functional properties of wheat flour is unclear. In the present study, two transgenic lines of the bread wheat overexpressing avenin-like b gene were generated to investigate the effects of Avenin-like b proteins on dough mixing properties. Sodium dodecyl sulfate sedimentation (SDSS) test and Mixograph analysis of these lines demonstrated that overexpression of Avenin-like b proteins in both transgenic wheat lines significantly increased SDSS volume and improved dough elasticity, mixing tolerance and resistance to extension. These changes were associated with the increased proportion of polymeric proteins due to the incorporation of overexpressed Avenin-like b proteins into the glutenin polymers. The results of this study were critical to confirm the hypothesis that Avenin-like b proteins could be integrated into glutenin polymers by inter-chain disulphide bonds, which could help understand the mechanism behind strengthening wheat dough strength.

Characterization of bread wheat cultivars (Triticum aestivumL.) by glutenin proteins

Glutenin polymers composed of HMW and LMW subunits are important contributors to the wheat end-use properties. Twenty-six winter wheat cultivars differing in bread processing quality were collected at the experimental fields of the Agricultural Institute Osijek, Croatia and Institute of the Field and Vegetable Crops Novi Sad, Serbia, in 2008/2009 season. The HMW glutenins composition and glutenin proteins content were determined by SDS-PAGE and RP-HPLC, respectively, with aim to determine the relationship between glutenin protein fractions and wheat quality properties. Significant differences were found between Croatian and Serbian cultivars in several quality attributes (GI, WA, DDT, DS and R/EXT) as well as in the content of total glutenins and LMW glutenins and GLI/GLU ratio. The dominant HMW subunits in analyzed cultivars were 2*, 7 + 9/7 + 8 and 5 + 10. Principal component analysis (PCA) confirmed the presence of association between HMW glutenins composition and GI, dough E, R and R/EXT, while the glutenins quantitative data showed pronounced relation with P, DDT, DS, E, R and R/EXT. GLI/GLU ratio had the opposite effect on these parameters.

A cysteine in the repetitive domain of a high-molecular-weight glutenin subunit interferes with the mixing properties of wheat dough

The quality of wheat (Triticum aestivum L.) for making bread is largely due to the strength and extensibility of wheat dough, which in turn is due to the properties of polymeric glutenin. Polymeric glutenin consists of high- and low-molecular-weight glutenin protein subunits linked by disulphide bonds between cysteine residues. Glutenin subunits differ in their effects on dough mixing properties. The research presented here investigated the effect of a specific, recently discovered, glutenin subunit on dough mixing properties. This subunit, Bx7.1, is unusual in that it has a cysteine in its repetitive domain. With site-directed mutagenesis of the gene encoding Bx7.1, a guanine in the repetitive domain was replaced by an adenine, to provide a mutant gene encoding a subunit (MutBx7.1) in which the repetitive-domain cysteine was replaced by a tyrosine residue. Bx7.1, MutBx7.1 and other Bx-type glutenin subunits were heterologously expressed in Escherichia coli and purified. This made it possible to incorporate each individual subunit into wheat flour and evaluate the effect of the cysteine residue on dough properties. The Bx7.1 subunit affected dough mixing properties differently from the other subunits. These differences are due to the extra cysteine residue, which may interfere with glutenin polymerisation through cross-linkage within the Bx7.1 subunit, causing this subunit to act as a chain terminator.

Redox regulation of glutenin subunit assembly in the plant endoplasmic reticulum

The glutenin fraction of wheat storage proteins consists of large polymers in which high- and low-molecular-weight subunits are connected by inter-chain disulfide bonds. We found that assembly of a low-molecular-weight glutenin subunit in the endoplasmic reticulum is a rapid process that leads to accumulation of various oligomeric forms, and that this assembly is sensitive to perturbation of the cellular redox environment. In endoplasmic reticulum-derived microsomes, low-molecular-weight glutenin subunits are subjected to hyper-polymerization, indicating that cytosolic factors play an important role in limiting polymer size. Addition of physiological concentrations of reduced glutathione is sufficient to maintain the original polymerization pattern of the glutenin subunits upon cytosol dilution. Furthermore, we show that a low-molecular-weight glutenin subunit can be glutathionylated in endoplasmic reticulum-derived microsomes, and that it can be directly reduced by glutathione in vitro. These results indicate that glutenin polymerization is sensitive to changes in the redox state of the cell, and suggest that the presence of a reducing cytosolic environment plays an important role in regulating disulfide bond formation in the endoplasmic reticulum of plant cells.

Relationship between endosperm cells redox homeostasis and glutenin polymers assembly in developing durum wheat grain

Assembly of glutenin polymers was examined for two contrasted durum wheat cultivars in connection with changes in the redox status of the endosperm cells that accompanied grain development. The evolutions of the redox state of ascorbate and glutathione, as well as the activities of antioxidant enzymes were measured. Changes in the size distribution profile and redox state of storage proteins were evaluated, with particular emphasis on protein-bound glutathione (PSSG). At the beginning of grain filling phase, the size distribution profile of proteins included an extra peak shoulder at about 40,000 g mol(-1). The shoulder was assimilated to free glutenin subunits as it disappeared concomitantly with the upturn in glutenin polymers accumulation. Irrespective of cultivars, small SDS-soluble polymers accumulated first, followed by larger and insoluble ones, attesting for a progressive polymerization. During the grain filling phase, catalase (EC 1.11.1.6) activity dropped, reaching a very low level at physiological maturity. During the same period, superoxide dismutase (EC 1.15.1.1) and glutathione reductase (EC 1.6.4.2) activities increased steadily while the equilibrium constant between GSSG and PSSG shifted from 10(-2) to unity. These results demonstrated that grain filling was accompanied by a continuous decrease in cellular redox potential. In this context, formation of protein-bound glutathione would represent a protective mechanism against irreversible thiol oxidation. Storage protein S-glutathionylation instead of limiting glutenin polymer assembly as it has been proposed might be a required intermediate step for glutenin subunits pairing.

Polymerization Reactions of Wheat Gluten: The Pretzel Case

Network formation of wheat gluten proteins (containing monomeric gliadin and polymeric glutenin) is essential for many wheat-based food products. The mechanisms of protein polymerization depend on processing conditions. Gluten disulfide (SS) cross-linking determines the end-product quality of many, if not all, wheat-based food products. Non-SS cross-links can be derived from dehydro amino acids after beta-elimination of cystine upon heating under alkaline conditions. In addition, isopeptide bonds can be induced during heating at neutral pH and under dry conditions, and Maillard cross-links can be formed when reducing sugars are heated in the presence of primary amino groups. The production of hard pretzels involves a heat and alkaline dip treatment followed by baking and drying to a final moisture content of 2%. This process induces formation of SS, dehydroalanine-derived, and Maillard-derived cross-links.

The relationship between gluten proteins and baking quality

Wheat, one of the most important cereals, is grown on the largest area in Hungary. During hydration of storage proteins of wheat – gliadin and glutenin – the gluten complex is evolved. The gliadin is responsible for the extensibility of gluten complex as well as the glutenin for the strength of gluten. The structure, composition and rheological properties of gluten proteins influence significantly the baking quality. The gliadin/glutenin ratio and the quality and structure of glutenin fraction play the most important role in evolving gluten complex. Changes in the steps of breadmaking technology also have effect on the quality of product. Several tests proved that the higher glutenin content increases the strength of dough while the higher gliadin content increases the extensibility of dough and decreases maximum resistance to extension. The monomer gliadins play a great part in plasticity of glutenin polymer. The quality of glutenin fraction significantly influences the evolving gluten complex, because of the spiral structure of glutenin which deforms under stress conditions, then the β-spiral structure resumes their original conformation by releasing from stress.The final quality of product evolves as a result of complex characteristics of wheat proteins, so detailed knowledge on the roles of different protein compounds is the base of the quality oriented product development.

Polymerization of Glutenin during Grain Development and Quality Expression in Winter Wheat in Response to Irrigation Levels

ABSTRACTChanges in the content and size distribution of glutenin were monitored using size‐exclusion‐high performance liquid chromatography (SE‐HPLC) during grain filling under field conditions in two seasons. Effects of irrigation levels on the constituent polypeptides (high molecular weight and low molecular weight glutenin unit), polymerization index (the percentage of sodium dodecyl sulfate [SDS]‐insoluble glutenins in total glutenins) of glutenin, glutenin macropolymer (GMP) particle size, dough mixing properties, and baking quality were examined. Drought or excess watering led to a reduced polymerization index at maturity resulting from modification of grain desiccation and accumulation of SDS‐insoluble glutenin. Glutenin particle size at maturity decreased under drought or excess watering and was associated with reduced ratio of a high molecular weight glutenin subunit to a low molecular weight glutenin subunit (HMW‐GS:LMW‐GS). The polymerization index of glutenin and GMP particle size were significantly positively correlated to dough stability times and loaf volume whereas no significant correlation existed among flour protein content, wet gluten content, dough stability times, and loaf volume. Therefore, dough mixing properties and baking quality were affected by irrigation levels mainly through changing the polymerization index of glutenin and GMP particle size in flour.