Characteristics and Protein Subunit Composition of Flour Mill Streams from Different Commercial Wheat Classes and Their Relationship to White Salted Noodle Quality

Proximate characteristics and protein compositions of selected commercial flour streams of three Australian and two U.S. wheats were investigated to evaluate their effects on the quality of white salted noodles. Wheat proteins of flour mill streams were fractionated into salt‐soluble proteins, sodium dodecyl sulfate (SDS)‐soluble proteins, and SDS‐insoluble proteins with a sequential extraction procedure. SDS‐soluble proteins treated by sonication were subsequently separated by nonreducing SDS polyacrylamide gel electrophoresis (SDS‐PAGE). There was a substantial amount of variation in distributions of protein content and protein composition between break and reduction mill streams. SDS‐insoluble proteins related strongly to differences in protein quantity and quality of flour mill streams. The soluble protein extracted by SDS buffer included smaller glutenin aggregates (SDS‐soluble glutenin) and monomeric proteins, mainly gliadin (α‐, β‐, γ‐, and ω‐types) and albumin and globulin. SDS‐soluble proteins of different flour mill streams had similar protein subunit composition but different proportions of the protein subunit groups. Noodle brightness (L) decreased and redness (a) increased with increased SDS‐insoluble protein and decreased monomeric gliadin. Noodle cooking loss and cooking weight gain decreased with increased glutenin aggregate (SDS‐soluble glutenin and SDS‐insoluble glutenin) and decreased monomeric gliadin. Noodle hardness, springiness, cohesiveness, gumminess, chewiness, tensile strength, breaking length, and area under the tensile strength versus breaking length curve increased with increased glutenin aggregate. Monomeric gliadin contributed differently to texture qualities of cooked noodles from glutenin aggregate. Monomeric albumin and globulin were not related to noodle color attributes (except redness), noodle cooking quality, and texture qualities of cooked noodles. The results suggested that variation in protein composition of flour mill streams was strongly associated with noodle qualities.     

Distribution of Protein Composition in Bread Wheat Flour Mill Streams and Relationship to Breadmaking Quality

Wheat protein quantity and composition are important parameters for wheat baking quality. The objective of this study was to use fractionation techniques to separate the proteins of flour mill streams into various protein fractions, to examine the distribution of these protein fractions, and to establish a relationship between protein composition and breadmaking quality. Nine break streams, nine reduction streams, and three patent flours obtained from three samples of Nekota (a hard red winter wheat) were used in this study. A solution of 0.3M NaI + 7.5% 1-propanol was used to separate flour protein into monomeric and polymeric proteins. The protein fractions, including gliadin, albumin+globulin, HMW-GS, and LMW-GS, were precipitated with 0.1M NH₄Ac-MeOH or acetone. The fractions were statistically analyzed for their distribution in the mill streams. The quantities of total flour protein and protein fractions in flour were significantly different among mill streams. The ratio of polymeric to monomeric proteins in break streams was significantly greater than in the reduction streams. The relationship between protein composition and breadmaking quality showed that the quantities of total flour protein, albumin+ globulin, HMW-GS, and LMW-GS in flour were significantly and positively correlated with loaf volume. The ratio of HMW-GS to LMW-GS had little association with loaf volume. The gliadin content in total flour protein was negatively and significantly correlated with loaf volume. These results indicated that the quantity and composition of protein among the mill streams was different, and this resulted in differences in breadmaking quality.     

施氮水平对小麦子粒蛋白质组分和加工品质的影响

选用两个优质小麦品种烟农15号和济麦19号,研究了施氮水平对小麦子粒蛋白质组分和加工品质的影响。田间试验设4个施氮水平,即N.0、120、240和360.kg/hm2。结果表明,施用氮肥对子粒发育前期清蛋白和球蛋白含量有明显的提高效应,但随子粒灌浆充实,这种效应逐渐削弱,到成熟期,施氮处理虽能提高子粒清蛋白和球蛋白的含量,但不同施氮水平间无明显差异。施用氮肥还能显著地提高子粒醇溶蛋白和麦谷蛋白的含量,尤其是子粒麦谷蛋白的含量,使子粒麦谷蛋白/醇溶蛋白比值提高。试验还表明,施用氮肥能明显提高子粒湿面筋含量,延长面团形成时间、面团稳定时间和断裂时间。综合分析看出,子粒醇溶蛋白和麦谷蛋白的含量以及麦谷蛋白/醇溶蛋白比值是影响小麦加工品质的重要因素,可以作为小麦品质育种中亲本及后代材料的选择、评价和优质栽培技术评价的依据。     

Shift of grain protein composition in bread wheat under summer drought events

Climate change bears the risk of more frequent drought stress in the northern hemisphere with more frequent early summer drought events affecting main grain crops. Winter wheat (Triticum aestivum L.) is susceptible for such drought events at the flowering and grain filling stages. After drought, the grain yield decrease of three hybrids was about 20% lower compared to three wheat lines analyzed. Wheat grain proteins are classified into four main components such as albumin and globulin, gliadin, and glutenin. The latter two are closely related to the baking quality of flour and might be affected by drought. However, detailed knowledge about the influence of drought on the synthesis of specific storage protein fractions is scarce. By analyzing the grain protein fractions by means of SDS‐PAGE technique, we detected an increase in grain protein content as well as in HMW and some LMW glutenin sub‐fractions. The glutenin fraction seems to be most variable in gene expression under different environmental scenarios such as drought. However, the protein yield as well as the grain yield may be strongly decreased, which might be not acceptable in practice.     

Studies on Effects of Microbial Transglutaminase on Gluten Proteins of Wheat. I. Biochemical Analysis

The enzyme transglutaminase (TG) is known to have beneficial effects on breadmaking. However, only limited information is available on the structural changes of gluten proteins caused by TG treatment. The effect of TG has, therefore, been systematically studied by means of model peptides, suspensions of wheat flours and doughs. The treatment of synthetic peptides mimicking amino acid sequences of HMW subunits of glutenin with TG results in isopeptide bonds between glutamine and lysine residues. To study the effect on gluten proteins, different amounts of TG (0 to 900 mg enzyme protein per kg) were dissolved in a buffer and added to wheat flour. The flour suspensions were incubated and centrifuged and the residues were successively extracted with water, a salt solution, 60% aqueous ethanol (gliadin fraction) and SDS solution including a reducing agent (glutenin fraction). The characterization of the fractions by amino acid analysis, SDS‐PAGE, gel permeation HPLC and reversed‐phase HPLC has indicated that the quantity of extractable gliadins decreases by increasing TG amounts. Among gliadins, the ω5‐type was affected to the greatest extent by the reduction of extractability, followed by the ω1,2‐, α‐ and γ‐types. The oligomeric portion of the gliadin fractions (HMW gliadin) was strongly reduced when flour was treated with 450 and 900 mg TG per kg of flour, respectively. In the first instance, the quantity of the glutenin fractions increased by the treatment of flour with 90 and 450 mg TG per kg of flour, and significantly decreased by the treatment of flour with 900 mg TG per kg of flour. Parallel to an increase in TG concentration, the amounts of glutenin‐bound ω‐gliadins and HMW subunits were strongly reduced, whereas the LMW subunits reached a maximal amount after treatment with 450 mg TG per kg of flour. The insoluble residue was almost free of protein when flour was treated with lower amounts of TG. Higher amounts led to a great increase of protein in the residues. The effects of TG on doughs were similar to those of flour suspensions, but less strongly pronounced probably due to the lower water content of the dough system. Sequence analysis of peptides from a thermolytic digest of the insoluble residue revealed that HMW subunits of glutenin and α‐gliadins were predominantly involved in cross‐links formed by TG treatment.     

Distribution of Glutathione in Millstreams and Relationships to Chemical and Baking Properties of Flour

Fourteen millstream flours, a straight‐run flour, bran, pollard, and germ were prepared separately from two Australian and two New Zealand wheat cultivars using a 650 kg/hr pilot roller mill. Glutathione (GSH) and oxidized glutathione (GSSG) were measured in all samples. The Australian cultivars had higher levels of GSH and GSSG than the New Zealand cultivars, and in all cultivars the levels in pollard and germ were considerably higher than in flour samples. Generally, the early break flours and early reduction flours had lower GSSH/GSSG levels than the tail‐end break and reduction flours. There was a strong correlation between GSH/GSSG and ash content in millstream flours, which indicated that much of the GSH/GSSG in the flour was likely to have derived from contamination by bran, aleurone (pollard), and germ. There were also moderate to strong correlations between GSH/GSSG and the cysteine content of all proteins in flour. GSH/GSSG correlated strongly with the albumin and globulin content of flour but not with gliadin and glutenin. The volume and crumb texture properties of bread made with millstream flours in the absence of ascorbic acid (AA) were negatively correlated with GSH/GSSG. The change in bread volume and texture properties when AA was added to dough (baking improver effect of AA), however, were poorly correlated with GSH/GSSG.     

Polymer Conformation Structure of Wheat Proteins and Gluten Subfractions Revealed by ATR‐FTIR

The polymer conformation structure of gluten extracted from a Polish wheat cultivar, Korweta, and gluten subfractions obtained from 2 U.K. breadmaking and biscuit flour cultivars, Hereward and Riband, was investigated using attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR). The results showed the conformation of proteins varied between flour, hydrated flour, and hydrated gluten. The β‐sheet structure increased progressively from flour to hydrated flour and to hydrated gluten. In hydrated gluten protein fractions comprising gliadin, soluble glutenin, and gel protein, β‐sheet structure increased progressively from soluble gliadin and glutenin to gluten and gel protein; β‐sheet content was also greater in the gel protein from the breadmaking flour Hereward than the biscuit flour Riband.     

Characterization of Glutenin Protein Fractions from Sequential Extraction of Hard Red Spring Wheats of Different Breadmaking Quality

Gluten proteins from two cultivars of hard red spring (HRS) wheat with good and poor breadmaking quality were fractionated into 13 fractions by sequential extraction with dilute hydrochloric acid. Each subfraction was characterized by multistacking (MS) SDS‐PAGE under nonreducing conditions, followed by imaging densitometry. The glutenin polymers from the origins of MS‐SDS‐PAGE were analyzed by SDSP‐PAGE under reducing conditions to determine the composition of high and low molecular weight subunits. The results showed that fractions differed significantly in glutenin‐to‐gliadin ratios and in the size distribution of glutenin polymers. The earlier precipitated fractions were composed of more gliadins but fewer glutenin polymers. However, the glutenin polymers gradually increased in their relative quantities with the residue having the largest glutenin‐to‐gliadin ratio. The size distribution of glutenin polymers differed significantly from early precipitated to later fractions. The relative quantities of glutenin aggregates at the 4% origins increased significantly. The ratio of high molecular weight (HMW) to low molecular weight (LMW) glutenin subunits increased significantly from early to intermediate fractions. Between the two cultivars, significant differences were found in the ratio of HMW to LMW glutenin subunits and quantity of SDS insoluble glutenin polymers in the residue fraction with the better breadmaking quality cultivar ND706 having a greater ratio than the cultivar Sharp. It was concluded that the size distribution of glutenin polymers played an important role in determining the differences in breadmaking quality between the good and poor HRS wheat cultivars.     

Protein Composition‐Functionality Relationships for a Set of Argentinean Wheats

Relationships between flour functional properties and protein composition were studied using a set of 138 Argentinean wheat samples. Among different protein groups, the incremental increase of gliadin with increasing grain protein content was highest followed by polymeric protein with albumin‐globulin content much lower. Functional properties could be divided into two groups based on dependence on protein composition. Properties such as dough extensibility and bake test loaf volume correlated highly with the percentage of polymeric protein in the grain. Properties such as mixograph dough development time were best correlated with the percentage of polymeric protein in the protein (PPP). Alveograph tenacity showed no significant dependence on PPP. as found previously for extensigraph maximum resistance, but it was correlated with the percentage of unextractable polymeric protein in the protein. Energy (W) appeared to be a more useful alveograph parameter for predicting flour quality.     

Immunochemical and Electrophoretic Analysis of the Modification of Wheat Proteins in Extruded Flour Products

Antibodies specific for wheat proteins were used to identify protein fractions modified during extrusion of Hard Red Spring wheat flour (14% protein) under four different combinations of extrusion conditions (18 and 24% feed moisture and 145 and 175°C die temperature). Antibody binding was assessed on immunoblots of proteins extracted from flour and extrudates separated by SDS‐PAGE. Antibodies to high molecular weight glutenin subunits (HMW‐GS) and to B‐group low molecular weight glutenin subunits (LMW‐GS) recognized intact subunits from both flour and extrudates. Antibodies to C‐group LMW‐GS had diminished binding to extruded proteins. Glutenin‐specific antibodies also recognized protein in the extrudates migrating as a smear at molecular weights higher than intact subunits, indicating cross‐linked proteins. Antibodies recognized albumins or globulins in flour but not in extrudates, evidence that these fractions undergo significant modification during extrusion. Acid‐PAGE and antibody reaction of gliadins extracted in 1M urea and in 70% ethanol revealed total loss of cysteine‐containing α, β, γ‐gliadins but no obvious effects on sulfur‐poor ω‐gliadins, suggesting gliadin modification involves replacing intramolecular disulfides with intermolecular disulfide cross‐links. Identifying protein fractions modified during different extrusion conditions may provide new options for tailoring extrusion to achieve specific textural characteristics.     

Intercultivar Variation in the Quantity of Monomeric Proteins,Soluble and Insoluble Glutenin,and Residue Protein in Wheat Flour and Relationships to Breadmaking Quality

A new fractionation procedure based on differential solubility was applied to wheat flour proteins to evaluate the relationship between protein fractions and functionality for breadmaking. Flour was initially extracted with 50% 1-propanol. Monomeric proteins (mainly gliadins) and soluble glutenin contained in the 50% propanol soluble extract were fractionated by selective precipitation of the glutenin by increasing the concentration of 1-propanol to 70%; monomeric proteins remain in the supernatant. Insoluble glutenin in the 50% propanol insoluble residue was extracted using 50% 1-propanol containing 1% dithiothreitol (DTT) at 60°C. Protein in the final residue was extracted using SDS with or without DTT. It comprised mainly Glu-1D high molecular weight glutenin subunits and nongluten polypeptides. For seven Canadian cultivars of diverse breadmaking quality, there was relatively little variation in the percentage of flour protein corresponding to monomeric proteins (48–52%) and residue protein (14–18%). In contrast, intercultivar variation in soluble and insoluble glutenin was substantial, with contents of 10–20% and 12–28% of flour protein, respectively. Soluble and insoluble glutenin were also highly correlated with physical dough properties, accounting for 83–95% of the variation of individual dough rheological parameters (except dough extensibility), and ≈ 74% of the variation in loaf volume. In contrast, monomeric and residue protein fractions were poorly associated with breadmaking quality. However, among the four protein fractions, only residue protein was significantly correlated (r = -0.79) with dough extensibility. The flour sample with the highest and lowest concentrations of insoluble and soluble glutenin, respectively, as well as marginally the lowest concentrations of monomeric and residue proteins was Glenlea, a cultivar of the Canada Western Extra Strong Red Spring wheat class which characteristically possesses distinctly strong dough mixing properties.     

Preparative Method for In Vitro Production of Functional Polymers from Glutenin Subunits of Wheat

An in vitro method for preparative‐scale production of artificial glutenin polymers utilizes a controlled environment for the oxidation of glutenin subunits (GS) isolated from wheat flour to achieve high polymerization efficiency. The functionality of in vitro polymers was tested in a 2‐g model dough system and was related to the treatment of the proteins before, during, and after in vitro polymerization. When added as the only polymeric component in a reconstituted model dough (built up from gliadin, water solubles, and starch fractions), in vitro polymers could mimic the behavior of native glutenin, demonstrating properties of dough development and breakdown. Manipulating the high molecular weight (HMW)‐GS to a low molecular weight (LMW)‐GS ratio altered the molecular weight distribution of in vitro polymers. In functional studies using the 2‐g mixograph, simple doughs built up from homopolymers of HMW‐GS were stronger than those using homopolymers of LMW‐GS. These differences may be accounted for, at least in part, by different polymer size distributions. The ability to control the size and composition of glutenin polymers shows the potential of this approach for investigating the effects of glutenin polymer size on dough function and flour end‐use quality.     

不同追施氮肥处理对冬小麦产量和品质的影响

以不同品质类型的2个小麦品种为试验材料,采用2因素随机区组设计,研究了不同品种和氮肥追施处理对产量和品质的影响.结果表明,在底肥量和追肥总量相同的条件下,适当增加开花期追施氮肥的比例有利于提高产量,处理间差异显著,品种间产量差异不显著;不同追肥处理对总蛋白含量影响不显著,但对清蛋白、醇溶蛋白和谷蛋白含量影响显著;追肥处...     

Globulin Expression in Grain of Australian Hard Wheat Cultivars Is Affected by Growth Environment

Our aim was to study changes in wheat proteomes across different growth locations as the first step in linking protein composition with functional changes in grains produced with commercial production systems. Soluble and insoluble proteins were extracted sequentially from grain of three commercial wheat cultivars grown at four locations in New South Wales, Australia, during a single season. Bands were separated with SDS‐PAGE and identified by peptide mass fingerprinting. Quantitative changes in the electrophoretic patterns were observed mainly in the insoluble polypeptides of molecular mass 40,000–70,000 for all three cultivars grown at two of the four locations. These proteins were identified as mainly globulin and serpin isoforms, as well as triticin. Other proteins with changed expression included disease‐resistance proteins, class III peroxidase, starch branching enzyme I, β‐amylase, and storage proteins. Two‐dimensional electrophoretic analysis was performed on two of the same wheat cultivars grown at one of the locations during two consecutive seasons. Protein spots that varied between seasons consisted of globulin and serpin isoforms, triticin, HMW glutenin, γ‐gliadin, starch branching enzyme IIb, and α‐amylase. The implications of the upregulation of globulin and triticin on whole meal flour quality, through their participation in polymerization of the gluten network, are considered.     

Physicochemical Changes in Nontraditional Pasta During Cooking

Physicochemical changes in the components of nontraditional spaghetti during cooking were reflected in the quality of the cooked product. Spaghetti formulations used were semolina (100%), whole wheat flour (100%), semolina/whole wheat flour (49:51), semolina/flaxseed flour (90:10), whole wheat flour/flaxseed flour (90:10), and semolina/whole wheat flour/flaxseed flour (39:51:10). Spaghetti quality was determined as cooking loss, cooked weight, and cooked firmness. Physicochemical analyses included total starch, starch damage, pasting properties, and protein quality and quantity of the flour mixes and spaghetti cooked for 0, 2, 4, 10, and 18 min. As cooking time progressed, total starch content decreased up to 5.7% units, starch damage increased up to 11.7% units, and both pasting parameters and protein solubility decreased significantly in all six formulations. Changes in the starch damage level, total starch content, and pasting properties of spaghetti correlated significantly (P < 0.05) with the cooking loss, cooked weight, and cooked firmness values recorded for the spaghetti. High levels of glutenin polymers and low levels of the albumin and globulin fractions were associated with low cooking losses and cooked weight and with high cooked firmness, indicating the involvement of these proteins in the cooked quality of nontraditional spaghetti.     

低能N+离子注入诱导小麦种子高分子量谷蛋白亚基和醇溶蛋白的变异

应用SDSPAGE和APAGE电泳技术,对不同剂量低能(25keV)N+离子注入小麦稳定品系CH3286的M3代种子储藏蛋白高分子量谷蛋白亚基和醇溶蛋白变异进行了系统的分析。结果表明低能N+离子束注入能有效地诱导小麦种子高分子量谷蛋白亚基的变异。高剂量(10.8×1016N+cm2)N+注入的诱变频率高于中剂量(7.2×1016N+cm2),其亚基总变异频率分别是13.7%和4.2%。不同位点的高分子量谷蛋白亚基对N+离子的敏感程度不同,其中以Glu1D最敏感,变异频率由大至小分别是Glu1D>Glu1B>Glu1A。低能N+离子束注入诱导的醇溶蛋白变异与高分子量谷蛋白亚基的变异有相似的规律。醇溶蛋白遗传区对N+离子的敏感程度也不同,其中ω醇溶蛋白最敏感,能产生较多的变异,其次是γ和β醇溶蛋白,最不敏感的是α醇溶蛋白。在M3代植株群体中筛选到一些农艺性状较稳定的高分子量谷蛋白亚基和醇溶蛋白变异株。     

水氮耦合对强筋冬小麦子粒蛋白质和淀粉品质的影响

在高肥力条件下,研究水氮耦合对小麦子粒产量、蛋白质含量及组成、蛋白质质量、淀粉含量及组成和淀粉品质的影响。结果表明,无论施氮与否,灌水均显著提高小麦子粒产量,同时显著降低子粒粗蛋白、单体蛋白及湿面筋含量;但不同灌水量间(W1、W2、W3)差异不显著。在低灌水频次(W0、W1)条件下,施氮具有明显的增产效应;而高灌水频次(W2、W3),施氮的增产效应不显著。随着灌水次数增加,谷蛋白总量保持稳定,而谷蛋白组分产生了显著的变化,其中可溶性谷蛋白含量呈上升趋势,不溶性谷蛋白含量和谷蛋白聚合指数呈下降趋势,粉质仪参数(形成时间和稳定时间)也呈下降趋势。小麦子粒蛋白质含量及组分和子粒品质均因施氮(N.168.kg/hm2)而有不同程度的提高,其中非面筋蛋白(清蛋白和球蛋白)的增加幅度高于面筋蛋白(醇溶蛋白和谷蛋白),可溶性谷蛋白增加幅度高于不溶性谷蛋白,即降低了谷蛋白聚合指数。水氮对子粒的淀粉含量及其组成的影响存在明显的交互效应。在不施氮肥条件下,随灌水次数增加,支链淀粉和总淀粉含量呈上升趋势;施氮条件下,各灌水处理(W1、W2、W3)的总淀粉和支链淀粉含量均显著高于不灌水处理(W0),但各灌水处理间差异不显著。随灌水次数增加,直链淀粉含量和直/支比均呈下降趋势,黏度仪指标(峰值黏度、稀值、最终黏度和反弹值)均呈上升趋势。施氮在低灌水频次(W0、W1)条件下促进支链淀粉的合成,同时降低直链淀粉含量和直/支比;高灌水频次(W2、W3)条件下则相反。     

Growth Environment Influences Grain Protein Composition and Dough Functional Properties in Three Australian Wheat Cultivars

The objectives of this study were to assess how functional properties of proteins in whole meal wheat (Triticum aestivum L.) flour vary across different growth environments. Grain from three commercial Australian Hard milling wheat cultivars was analyzed from four growth locations in 2008 and from two of the corresponding cultivars and locations in 2009. The protein content of the grain, soluble and insoluble extractable protein fractions, swelling index of glutenin (SIG), glutenin‐to‐gliadin ratio (Glu:Gli), percent unextractable polymeric protein (%UPP), and dough properties including force at maximum resistance (Rmax) and extensibility were measured. Based on analysis of variance of aggregated data for the cultivars, growth locations, and seasons, growth environment factors made significant contributions to variability in the total grain protein, Glu:Gli ratio, %UPP, SIG, Rmax, and extensibility of the wheat flour. Variability of protein content of the soluble and insoluble extractable protein fractions was mostly owing to genotype.     

Functionality of Barley Proteins Extracted and Fractionated by Alkaline and Alcohol Methods

This research optimized the extraction of different protein fractions from barley grains and assessed the physicochemical properties of the fractions obtained. Pearling was first used to remove the grain's outer layers (mainly bran and germ) so that the barley cytoplasmic proteins (albumin and globulin) would be enriched in the pearling flour (PF), while endosperm proteins (hordein and glutelin) would be enriched in the pearled grain flour (PGF). Salt, alcohol, and alkaline solutions were then used to extract different barley protein fractions from PF and PGF. The effects of extraction solvent type, pH, temperature, and extraction time on protein content and extraction efficiency were studied. Aqueous ethanol (55%, v/v) efficiently extracted barley hordein from PGF at 60°C, whereas pH 11.5 alkaline solution was the most efficient for extracting both cytoplasmic and endosperm proteins from barley PF and PGF at 23°C. Subunit molecular weight, amino acid composition, and the functional properties of each isolated barley protein fraction were investigated. Barley glutelin demonstrated superior oil‐binding property and emulsifying stability, whereas barley hordein exhibited good foaming capacity.     

Alkylation of Free Thiol Groups During Extraction: Effects on the Osborne Fractions of Wheat Flour

Wheat proteins are classified according to solubility into the so‐called Osborne fractions. Because wheat flour contains both free thiol and disulfide groups, thiol–disulfide interchange reactions are possible during extraction. Osborne fractionation of 12 different wheat flour samples was performed in the presence of N‐ethylmaleinimide (NEMI) to alkylate free thiol groups and without addition of NEMI (control). The addition of NEMI during extraction tended to decrease the content of gliadins (predominantly α‐gliadins) and caused an increase of the content of glutenins in most flour samples. Thus, alkylation of free thiol groups during extraction led to a decline of the gliadin/glutenin ratio from 2 (control) to approximately 1.5 (NEMI). NEMI and control gliadins were separated by gel‐permeation HPLC into an oligomeric subfraction (high‐molecular‐weight [HMW] gliadins) and two monomeric subfractions. In most flours (8 of 12), the addition of NEMI led to a significant increase of the content of HMW gliadins. HMW gliadins from cultivar Akteur wheat were preparatively isolated from NEMI and control gliadins and characterized by HPLC, sodium dodecyl sulfate polyacrylamide gel electrophoresis, and N‐terminal sequencing. HMW gliadin isolated in the presence of NEMI had a significantly higher content of low‐molecular‐weight glutenin subunits and disulfide‐bound cysteine as well as a lower content of α‐gliadins and disulfide‐bound glutathione compared with the control.