Studies on protein and its high‐molecular‐weight subunit composition in relation to chapati‐making quality of Indian wheat cultivars

In order to predict the suitability of wheat for chapati making, 15 Indian wheat cultivars were studied for various protein characteristics in relation to chapati‐making quality. The cultivars varied considerably in their protein characteristics and chapati‐making potential. Results clearly indicated that both quantitative and qualitative characteristics of proteins influenced the chapati‐making potential of cultivars. Puffed height, the important qualitative parameter of chapati, was positively correlated with protein content (r = 0.62, p < 0.05), gluten content (r = 0.79, p < 0.01), sodium dodecyl sulphate (SDS) sedimentation value (r = 0.57, p < 0.05) and Glu‐1 quality scores of high‐molecular‐weight (HMW) subunits (r = 0.66, p < 0.01). Overall quality score of chapati was positively correlated with gluten content (r = 0.64, p < 0.01), SDS sedimentation value (r = 0.60, p < 0.05) and Glu‐1 score (r = 0.58, p < 0.05). HMW subunit composition varied considerably among cultivars. Cultivars having 5 + 10 subunits at the Glu‐1D chromosome, a protein content of about 130 g kg^?1 and SDS sedimentation value around 75 ml yielded excellent chapatis, while those having 2 + 12 subunits, a protein content of about 115 g kg^?1 and SDS sedimentation value around 55 ml resulted in poor chapatis. Interestingly, the presence of the 1BL/1RS chromosome in cultivars had no adverse effect on chapati quality. © 2003 Society of Chemical Industry     

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。     

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     

The HMW glutenin subunit composition of Canadian wheat cultivars and their association with bread-making quality

The proteins of 70 Canadian-grown wheat cultivars were fractionated by SDS-PAGE to determine their HMW glutenin subunit composition. On the basis of previously established relationships between individual subunits and measures of bread-making quality, Glu-1 scores were calculated for 67 cultivars. The three cuhivars Chinook, Cypress and Supreza were found to contain novel HMW glutenin subunits previously uncatalogued. The Glu-1 scores accounted for 59–69% of the variation in bread-making quality of these cultivars whereas flour ash accounted for none. The implications of these results to wheat breeding programmes are discussed.     

Variation in concentrations of high-molecular-weight glutenin subunits and macropolymers in wheat grains of a recombinant inbred lines population and in two contrasting eco-sites in China

BACKGROUND: Concentrations of high‐molecular‐weight glutenin subunits and macropolymers in wheat grains are important indicators of grain quality, which are genetically determined and affected by environmental factors. The 6 VS·6AL translocation chromosome segment is reported to own high powdery mildew and yellow rust resistance genes of Pm21 and Yr26. This study investigated the variation in concentrations of high‐molecular‐weight glutenin subunits (HMW‐GS) and glutenin macropolymer (GMP) in response to the 6 VS·6AL translocation segment and the two contrasting sites. RESULTS: Large variations in concentrations of HMW‐GS and GMP were observed within lines containing different HMW‐GS compositions and between the contrasting eco‐sites. However, 6 VS·6AL chromosome translocation segment showed no significant effects on concentrations of HMW‐GS and GMP. In addition, HMW‐GS concentration was also found to be significantly correlated with the GMP concentration. CONCLUSION: Concentrations of HMW‐GS and GMP are largely affected by the eco‐sites and the composition of HMW‐GS, whilst not by the presence of 6 VS·6AL chromosome segment translocation. The 6 VS·6AL translocation is suggested as potential donor for breeding wheat cultivars for high resistence to powdery mildew and yellow rust with less risk of undesirable effects on grain quality. Copyright © 2012 Society of Chemical Industry     

Importance of amounts and proportions of high molecular weight subunits of glutenin for wheat quality

 High molecular weight (HMW) subunits of wheat glutenin are generally considered to play a key role in gluten formation and structure, and to be closely related to wheat quality. Though quantities of HMW subunits in flour have been proposed to be as important for wheat quality as their structures, only few quantitative data are available in the literature. Therefore, two assortments of wheat consisting of 13 international and 16 German cultivars were analyzed for their contents and proportions of single HMW subunits using an extraction and HPLC procedure on a micro-scale. The results were compared with quantitative data from the literature that were obtained by sodium dodecylsulfate polyacrylamide gel electrophoresis combined with densitometry or by reversed-phase HPLC combined with UV detection. The quantitative analyses demonstrated that the contents of HMW subunits varied within a broad range dependent on genotype and growing conditions. The proportions of subunits within a given subunit combination, however, varied only within a small range. Generally, subunits 2, 5, 7, 10 and 12 were major components and subunits 1, 2*, 6, 8 and 9 were minor components. The levels of HMW subunits were highly correlated to dough development time, maximum resistance of dough and gluten, and bread volume. Among HMW subunits the x-type components (subunits 1–7) were much more important than the y-type components (subunits 8–12). In particular, the presence of subunit 5 (which has an additional cysteine residue) and of subunit 7 (which occurs in the greatest amounts) contributed to high wheat quality. Received: 22 June 1999     

Relationship between glutenin subunit composition and gluten strength measurements in durum wheat

Durum breeders use a range of techniques in the development of new cultivars. An important selection criterion is the rheological properties of semolina dough and durum wheat breeders use this criterion in the development of new cultivars using a range of techniques. Because of the need to process large numbers of genotypes encountered in breeding programs, methods that are inexpensive, rapid, require small amounts of sample and that correlate with semolina quality are desirable. Using breeding material, this study investigated the relationship between the glutenin subunit composition and two traditional tests of gluten strength, gluten index (GI) and mixograph. Two sample sets of durum wheat breeding lines and cultivars, one grown in Canada (n = 229) and the other grown in Australia (n = 139) were analysed for GI, mixograph and both high molecular weight (HMW) and low molecular weight (LMW) glutenin subunits by SDS‐PAGE. Nine different HMW and 14 different LMW allelic combinations were found. In the Canadian set, the most frequent LMW alleles were aaa, bba, caa and cfa while in the Australian set, caa was predominant. For the HMW subunits, the most common allelic groups were Glu‐A1c/Glu‐B1d (null, 6 + 8) and Glu‐A1c/Glu‐B1b (null, 7 + 8) with fewer numbers of Glu‐A1c/Glu‐B1e (null, 20) in both sample sets. LMW subunits were more important contributors to gluten strength than HMW subunits with the rank for higher GI according to the LMW allele (Canadian set) being caa = aaa > bba and aaa > cfa while HMW subunits 6 + 8 = 7 + 8 > 20. Similarly, using the mixograph, strength ranking for the LMW alleles was aaa > cfa = bba and HMW subunit 20 gave poorer rheological properties. For some samples with a good LMW allelic group a low GI was observed and vice versa. Further characterisation of the protein composition in these samples showed the GI results could be explained by polymeric/monomeric (P/M), glutenin/gliadin (Glu/Gli) and HMW/LMW ratios or the proportion of unextractable polymeric protein. © Crown in the right of the State of New South Wales, Australia; and for the Department of Agriculture and Agri‐Food, Government of Canada, © Minister of Public Works and Government Services Canada 2005. Published for SCI by John Wiley & Sons, Ltd.     

Fractionation of Algerian common wheat proteins by HPLC and sodium dodecyl sulfate-polyacrylamide gel electrophoresis; relationship with technological quality

Sixteen Algerian common wheat genotypes have been analysed during three harvests for their protein characteristics. SE- HPLC analysis showed some relation between the percentages or the absolute amounts of the glutenin fractions F1, F2 or F1/F2 ratio and several technological parameters. However, the relative amount of SDS unextractable polymeric glutenins in total polymeric glutenins or in total polymeric proteins and the ratios of the SDS unextractable proteins, extracted from the residues after sonication, in extracted total polymeric proteins seem to play a more determinant role in wheat strength. If no interesting links were observed between the HMW/LMW glutenin ratios determined by RP-HPLC and the technological quality characteristics, HMW glutenin SDS-PAGE analysis and technological and biochemical tests once more showed the superiority of the 5+10 HMW glutenin subunit pair compared with 2+12 allelic pair in the determination of the strength, its aptitude to give more aggregate of large molecular sizes, and higher HMW/LMW glutenin ratios.     

Expression of the 1Ax1 transgene in an elite Chinese wheat variety and its effect on functional properties

BACKGROUND: The transfer of transgenes from ‘model’ wheat genotypes into elite wheat cultivars using conventional plant breeding is an alternative strategy for improving the dough quality of wheat. Thus a cross was made between a popular Chinese elite wheat cultivar of the Yangzi River down‐central area that expresses high‐molecular‐weight glutenin subunit (HMW‐GS): 1Bx7 + 1By8 plus 1Dx2 + 1Dy12, and a model transgenic wheat line B102‐1‐2 which over‐expresses HMW‐GS 1Ax1 in an L88‐31 genetic background that includes HMW‐GS 1Bx17 + By18. RESULTS: F₁ to F₆ generations of crosses between B102‐1‐2 (paternal) and Emai (maternal) were analysed for their HMW‐GS compositions, allowing the selection of pure F₆ lines over‐expressing HMS‐GS 1Ax1 in the presence of the endogenous HMW‐GS: 1Bx7 + 1By8 with 1Dx2 + 1Dy12, and 1Bx17 + 1By18 with 1Dx2 + 1Dy12. Analysis of the F₆ lines showed changes in the extensograph parameters, with increases in peak area, resistance to extension, and extensibility and peak resistance to extension, similar to those observed in the transgenic paternal line B102‐1‐2. CONCLUSION: This work showed that the expression levels of the 1Ax1 transgene and the effects on dough properties were similar in the transgenic parental line B102‐1‐2 and the F₆ progeny generated from a cross with an elite Chinese cultivar Emai. The feasibility of using transgenic lines expressing HMW‐GS subunits in conventional breeding programmes was demonstrated. Copyright © 2009 Society of Chemical Industry     

The relationship between HMW glutenin subunit composition and the bread-making quality of British-grown wheat varieties

Based on previous work, which related individual HMW glutenin subunits to bread-making quality by genetical analysis, quality scores were assigned to each of the commonly occurring subunits. The grain proteins of 84 home-grown wheat varieties were fractionated by SDS—PAGE to determine their HMW glutenin subunit composition. The quality scores of each of the subunits were summed to create a Glu-1 quality score for each variety. The results indicated that 47-60% of the variation in the independently established bread-making qualities of this set of varieties could be accounted for by variation in HMW subunits of glutenin. The presence or absence in the varieties of a translocated chromosome, which consisted of the long arm of 1B and the short arm of 1R from rye, was also established because of its known association with poor bread-making quality. A correction factor was applied to the Glu-1 quality score of those varieties that contained the 1 BLURS chromosome. The variations in the rye-adjusted Glu-1 quality scores were compared with those of the bread-making qualities of the varieties, and the proportion of variation in quality accounted for was raised to 55-67%. The Glu-1 quality score and the biscuit-making qualities of the same set of varieties were negatively related. The results are discussed in relation to future strategies recommended to wheat breeders for developing new varieties with improved bread-making quality.     

Protein characteristics and peroxidase activities of different Indian wheat varieties and their relationship to chapati-making quality

Different wheat varieties grown at a single geographical location were evaluated for protein quantity and quality, rheological properties, and activities of peroxidase as well as polyphenol oxidase. The protein content in these varieties ranged from 11.6 to 14.6%, farinograph water absorption ranged from 70 to 76%, and the damaged starch content varied from 12.3 to 16.3%. The total protein content of whole wheat flours significantly correlated to stiffness (R/E values) of the dough (r=0.73, p<0.05); however, it did not influence any of the quality parameters of chapati. However, the protein quality parameter, Glu-1 score, which reflects the high molecular weight (HMW) glutenin subunit composition, correlated significantly to the cutting force, which indicates the texture of chapati (r=0.78, p<0.05). The quantity of low molecular weight protein fraction having molecular weight of 20 kDa showed significant correlation to over all quality scores of chapati (r=0.78, p<0.05). The color of chapatis was significantly correlated to color of dough (r=0.76, p<0.05), which became darker on resting. Peroxidase activity greatly influenced the color of chapatis (r=0.81, p<0.05).     

EFFECT OF COMPOSITION OF GLUTHNIN SUBFRACTIONS ON RHEOLOGICAL PROPERTIES OF WHEAT

Gluten extracted from defatted flours of cv. Aubaine (extra‐strong), Hereward (strong) and Riband (weak) was separated into five different fractions (R2 to R6) by sequential centrifugation and addition of sodium chloride. A seven‐minute mixing time was used to carry out fractionation on the basis of depolymerization of glutenin macropolymers (GMP). Depolymerization of GMP occurred at much higher rates in dough of the weak cultivar compared to the strong and extra‐strong cultivars. Polypeptide compositions of different ghttenin fractions were determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis under reduced and non‐reduced conditions, followed by densitometric scanning of stained patterns. The amount of HMW‐glutenin subunits decreased and LMW‐glutenin subunits increased correspondingly in each cultivar with the fractionation from R₂ to R₆. The rheological behavior of the fractions was analyzed by small deformation rheological tests (strain sweep and frequency tests). The high molecular weight fraction (R₂) from extra‐strong wheat had a higher vahte of G' and a lower tan δ value as compared to strong and weak bread‐making wheats. The moduli of HMW glutenin fractions (R2 and R3) were frequency independent and promoted the network properties, whereas moduli of LMW glutenin fractions were frequency dependent and gave rise to a plasticizing effect. Therefore, it was concluded from the present studies that HMW‐glutenin subunits are not the only factors governing good bread‐making quality but their proportions in relation to low molecular weight glutenin subunits is equally important in sinking a balance between viscous and elastic properties essential for bread making performance.     

Quantification of monomeric and polymeric wheat proteins and the relationship of protein fractions to wheat quality

Wheat protein composition is important for understanding the biochemical basis of wheat quality. The objective of this study was to design a simple protein fractionation protocol with low cross‐contamination and to show that these protein fractions were associated with wheat quality. The protocol consists of three sequential extractions from 100 mg of flour with 7.5% propan‐1‐ol and 0.3 M sodium iodide (monomeric‐rich protein), 50% propan‐1‐ol (soluble glutenin‐rich protein) and 40% propan‐1‐ol and 0.2% dithiothreitol (insoluble glutenin‐rich protein). Nitrogen content of protein solubility groups was determined from dry residues using an automated combustion nitrogen analyser. About 90% of the total protein in the flour was solubilised. Cross‐contamination of protein fractions was evaluated by SDS‐PAGE, SE‐HPLC and RP‐HPLC. Variation in nitrogen content of the protein solubility fractions was lowest for monomeric‐rich protein (<2%) and insoluble glutenin‐rich protein (<4%). Three wheats with similar high‐molecular‐weight (HMW) glutenin subunit composition, Alpha 16, Glenlea and Roblin, varied significantly (P ≤ 0.05) in the proportion of monomeric‐rich and insoluble glutenin‐rich protein in the flour. Dough rheological properties were directly related to the proportion of insoluble glutenin‐rich protein and inversely related to the proportion of monomeric‐rich protein. The protocol was validated using an expanded set of 11 wheats which also showed that inter‐cultivar differences in the proportion of monomeric‐rich, insoluble glutenin‐rich protein and glutenin‐to‐gliadin ratio in the flour governed dough rheological properties such as mixograph, farinograph and microextension tests. The protocol has merit for quality screening in wheat‐breeding programmes when the sample size is too small or when time constraints limit the ability to perform traditional rheological tests. For the Department of Agriculture and Agri‐Food, Government of Canada, Copyright © Minister of Public Works and Government Services Canada 2003. Published for SCI by John Wiley & Sons, Ltd.     

Improving wheat for bread and tortilla production by manipulating glutenin‐to‐gliadin ratio

Gluten, starch, water soluble material, and glutenin‐rich and gliadin‐rich proteins were extracted from three Canadian wheat cultivars representing the Canada Western Red Spring (CWRS) (cv Roblin), Canada Western Extra Strong (CWES) (cv Glenlea) and Canada Prairie Spring (CPS) (cv AC Crystal) classes having glutenin‐to‐gliadin (Glu:Gli) ratios of 0.70, 0.75 and 0.85 respectively, all giving the same high‐molecular‐weight glutenin subunit score (Glu‐1 score) of 10. The resulting fractions were reconstituted to produce 18 mixtures of flour components, representing all combinations of Glu:Gli ratio and protein content observed in the original three flours. Dough rheological properties and baking (bread and tortilla) performance were determined using small‐scale techniques. Within any of the cultivars, increasing the Glu:Gli ratio in a reconstituted dough system had significant effects on dough and end‐use properties, causing increases in mixograph development time (MDT), maximum resistance (Rmax), pan bread loaf volume, tortilla dough maximum resistance and cooked tortilla puncture force. The CWRS wheat Roblin, proved to be best suited for pan bread at higher protein content and higher Glu:Gli ratio, and also produced a high protein tortilla of large diameter at a Glu:Gli ratio of 0.70. The CPS flour, AC Crystal, was good for making tortillas at protein contents of 110–130 g kg⁻¹ and at its original ratio of 0.85. The CWES wheat Glenlea, did not perform as well in bread or tortilla‐making but in its role as a blending wheat, altering the Glu:Gli ratio of Glenlea to 0.70 may have an advantage by lowering mixing time without compromising baking properties. Manipulating the Glu:Gli ratio may make a wheat cultivar suitable for a particular end‐product. For the Department of Agriculture and Agri‐Food, Government of Canada, © Minister of Public Works and Government Services Canada 2005. Published for SCI by John Wiley & Sons, Ltd.     

Molecular Analysis of the Polymeric Glutenins with Gliadin‐Like Characteristics That Were Produced by Acid Dispersion of Wheat Gluten

We had earlier shown that the dispersion of wheat gluten in acetic acid solution conferred gliadin‐like characteristics to the polymeric glutenins. To elucidate the molecular behavior of its polymeric glutenins, the characteristics of gluten powder prepared from dispersions with various types of acid were investigated in this study. Mixograph measurements showed that the acid‐treated gluten powders, regardless of the type of acid, had dough properties markedly weakened in both resistance and elasticity properties, as though gliadin was supplemented. The polymeric glutenins extracted with 70% ethanol increased greatly in all acid‐treated gluten powders. Size exclusion HPLC and SDS‐PAGE indicated that the behavior of polymeric glutenins due to acid treatment was attributed to their subunit composition rich in high molecular weight glutenin subunit (HMW‐GS) and not their molecular size. The gluten prepared with the addition of NaCl in acid dispersion had properties similar to those of the control gluten. The results suggest that ionic repulsion induced by acid dispersion made the polymeric glutenins rich in HMW‐GS disaggregate, and therefore, act like gliadins.     

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...     

Phytate and mineral content in different milling fractions of some Pakistani spring wheats

Six Pakistani wheat cultivars, namely C-273, Inqulab-91, Pasban-90, Parwaz-94, Shahkar-95 and Rohtas-90, were included in the present study. The kernel weight of the wheat cultivars varied from 31.43 to 36.76 g (per thousand kernels), Parwaz-94 having the highest and Rohtas-90 having the lowest. The test weight of cultivars ranged from 70.23 (Shakar-95) to 76.13 kg hL^–1 (Pasban-90). The bran contained the highest amount of phytic acid (6.12%) in C-273 followed by whole-wheat flour (2.23%) in Inqulab-91, and straight-grade flour (0.24%) in Parwaz-94. The phytate content was reduced during the baking of bread and chapati. The bread scores and other quality characteristics varied significantly among cultivars. The total bread scores ranged from 35.20 to 42.00, out of a possible fifty, with Parwaz-94 being the highest. The concentration of minerals varied widely in different milling fractions of various wheat cultivars. The concentration of Cu, Fe, Mn and Zn ranged from 5.00 to 52.50, 26 to 147.50, 0.00 to 97.00, 9.0 to 80.80 ppm, respectively, in different milling fractions of the wheat cultivars. The total chapati scores ranged from 22.40 to 24.20 of a possible score of 30. The minimum chapati scores were found in Rohtas-90 and Parwaz-94, while Inqulab-91 produced the maximum score.     

The effect of aphid infection and cultivar on the protein content governing baking quality of wheat flour

BACKGROUND: Aphids cause both quantitative and qualitative yield losses in cereals. Aphid feeding resulted in a significant decrease in gliadin/glutenin ratio in soft‐kernel wheat. Effect of aphid feeding on hard‐kernel wheat was examined. RESULTS: Plants of two different hard‐wheat cultivars were artificially infected by two aphid species: Sitobion avenae and Diuraphis noxia. Three different levels of caging regulated aphid density. Aphid density was highest in the cages, followed by open cages and lowest under no‐cage conditions. Numbers of D. noxia were generally higher compared to those of S. avenae. There was no significant difference in head length, mean kernel number/head, mean kernel mass/head or mean individual kernel mass between the two cultivars. Glutenin, gliadin and total protein content was analysed using size‐exclusion HPLC. Quality parameters of wheat flour were significantly different between the two cultivars. Gliadin content, total protein content and gliadin/glutenin ratio were significantly higher in Mv Magdaléna compared to Mv Magvas regardless of the level of caging and infestation, while glutenin content of uninfected Mv Magvas was significantly higher than that of Mv Magdaléna in the open cages. Aphid feeding did not induce any significant reduction in the gliadin, total protein content and gliadin/glutenin ratio of the examined hard wheat cultivars. CONCLUSION: Individual kernel mass reduction is the major factor in yield loss caused by aphids. Aphid feeding did not change the protein structure of hard‐kernel wheat. Copyright © 2007 Society of Chemical Industry     

Comparative investigations of gluten proteins from different wheat species I. Qualitative and quantitative composition of gluten protein types

In contrast to the hexaploid common (bread) wheat, little information is available on the qualitative and quantitative compositions of gluten proteins from other cultivated wheat species. Therefore, representatives of hexaploid spelt, tetraploid durum wheat and emmer, and diploid einkorn were compared with three classes of common wheat (winter wheat, spring wheat, wheat rye hybrid). The flours were extracted to yield total endosperm proteins and the gluten protein fractions (gliadins and glutenin subunits). The extracts were characterised using sodium dodecyl sulfate polyacrylamide gel electrophoresis and reversed-phase HPLC; both methods revealed that gluten protein groups and types known from common wheat (ω-, α-, γ-gliadins, HMW and LMW subunits of glutenin) were present in all species. The HPLC platterns of gliadins and glutenin subunits from species with the same genome composition (common wheat/spelt or durum wheat/emmer) were related, and those of einkorn quite different. According to the quantities determined by reversed-phase HPLC, α-gliadins were predominant in most cases, followed by γ-gliadins and LMW subunits; ω-gliadins and HMW subunits were generally minor components. Common wheats were characterised by the highest proportions of total glutenins and HMW subunits, which are known to be important for breadmaking quality. Moreover, the lower ratio of gliadins to glutenins was typical. Emmer had the lowest proportions of total glutenins and of HMW and LMW subunits, together with einkorn the highest proportion of α-gliadins, and, by far, the highest ratio of gliadins to glutenins. The values for spelt and durum wheat were mostly in a medium range between common wheats, emmer, and einkorn, respectively. Amongst common wheats, spring wheat was characterised by more balanced quantities of α- and γ-gliadins, and wheat rye hybrid by the highest proportions of ω-gliadins. Received: 26 November 1999     

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.