Total Glutenin Research Articles

Variations in the quality parameters and gluten proteins in synthetic hexaploid wheats solely expressing the Glu-D1 locus

This study evaluated the quality potential of seven synthetic hexaploid wheats (2n=6x=42, AABBDD) expressing only allelic variation at Glu-D1 of Aegilops tauschii (SHWSD). Major quality parameters related to dough strength, gluten proteins (including high-molecular-weight glutenin subunits (HMW-GS) and low-molecular-weight glutenin subunits (LMW-GS), gliadins), and their ratios between SHWSD and the weak gluten wheat control Chuannong 16 (CN16) were measured in at least three environments (except STD7). The zeleny sedimentation value (ZSV), dough development time (DDT), dough stability time (DST), and farinograph quality number (FQN) of SHWSD were considered stable under different environments, with their respective ranges being 8.00–17.67 mL, 0.57–1.50 min, 0.73–1.80 min, and 9.50–27.00. The ZSV, DDT, DST, and FQN of SHWSD were smaller than those of CN16, suggesting that SHWSD had a weaker dough strength than CN16. Although SHWSD had a lower gluten index than CN16, its wet and dry gluten contents were similar to or even higher than those of CN16 in all environments tested. The protein content of grains (12.81–18.21%) and flours (14.20–20.31%) in SHWSD was higher than that in CN16. The amount of HMW-GS in SHWSD sharply decreased under the expression of fewer HMW-GS genes, and the LMW-GS, gliadins, and total glutenins were simultaneously increased in SHWSD in comparison with CN16. Moreover, SHWSD had higher ratios of LMW-GS/glutenin and gliadin/glutenin but a lower ratio of HMW-GS/glutenin than CN16. These results provide necessary information for the utilization of SHWSD in weak-gluten wheat breeding.

Response of Wheat Yield and Protein-Related Quality on Late-Season Urea Application

Field experiments were conducted, aiming to evaluate whether the late-season foliar urea application (35 kg N ha−1) is effective in improving grain yield and protein-related quality in ten common wheat cultivars during two consecutive growing seasons. On average, late urea application significantly (p < 0.05) increased grain yields, thousand kernel, and hectolitre weight. The total grain protein significantly (p < 0.05) increased by 17.5% under urea application, while dough mixing behaviour was improved by increasing flour water absorption and reducing the degree of softening. Considering dough elastic properties, the changes in dough energy and maximum resistance under urea application were strongly cultivar dependent and their values compared to control varying from −12.7% to +42.4% and −25.1% to +7.7%, respectively. The distribution of grain storage proteins was significantly influenced by late urea application, but to a lesser extent than the total grain proteins. The proportion of total gliadins, α- and γ-gliadins increased by 5.3%, 5.8%, and 6.5%, respectively, while total glutenins and high-molecular weight glutenins decreased by 4.5% and 7.4%, respectively. In summary, the late-season application of urea has greatly improved the protein-related quality without considerable disruption of the storage proteins composition.

Quantitative traits loci mapping and molecular marker development for total glutenin and glutenin fraction contents in wheat

BackgroundGlutenin contents and compositions are crucial factors influencing the end-use quality of wheat. Although the composition of glutenin fractions is well known, there has been relatively little research on the genetic basis of glutenin fractions in wheat.ResultsTo elucidate the genetic basis for the contents of glutenin and its fractions, a population comprising 196 recombinant inbred lines (RILs) was constructed from two parents, Luozhen No.1 and Zhengyumai 9987, which differ regarding their total glutenin and its fraction contents (except for the By fraction). Forty-one additive Quantitative Trait Loci (QTL) were detected in four environments over two years. These QTL explained 1.3% - 53.4% of the phenotypic variation in the examined traits. Forty-three pairs of epistatic QTL (E-QTL) were detected in the RIL population across four environments. The QTL controlling the content of total glutenin and its seven fractions were detected in clusters. Seven clusters enriched with QTL for more than three traits were identified, including a QTL cluster 6AS-3, which was revealed as a novel genetic locus for glutenin and related traits. Kompetitive Allele-Specific PCR (KASP) markers developed from the main QTL cluster 1DL-2 and the previously developed KASP marker for the QTL cluster 6AS-3 were validated as significantly associated with the target traits in the RIL population and in natural varieties.ConclusionsThis study identified novel genetic loci related to glutenin and its seven fractions. Additionally, the developed KASP markers may be useful for the marker-assisted selection of varieties with high glutenin fraction content and for identifying individuals in the early developmental stages without the need for phenotyping mature plants. On the basis of the results of this study and the KASP markers described herein, breeders will be able to efficiently select wheat lines with favorable glutenin properties and develop elite lines with high glutenin subunit contents.

Gluten Protein Compositional Changes in Response to Nitrogen Application Rate

Field trials were conducted to evaluate the effect of nitrogen level on wheat protein content and composition in 16 cultivars over two years at three locations. The nitrogen treatment comprised two nitrogen levels, 0 kg ha−1 as low and 100 kg ha−1 as high nitrogen, applied as top dressings of 50 kg nitrogen per ha at tillering and stem extension growth stages. Increased nitrogen level generally enhanced grain protein by 11.3% (11.5% vs. 12.8%). Considering protein composition determined by reversed phase–high-pressure liquid chromatography, higher nitrogen supply generally enhanced the proportion of total gliadins, α-gliadins, γ-gliadins and high-molecular-weight glutenin subunits by 1.1%, 2.0%, 3.7%, 0.6% and 0.9%, respectively, and reduced albumins and globulins, ω-gliadins, total glutenins and low-molecular-weight glutenin subunits by 1.1%, 1.7%, 1.9% and 3.2%. Under a high nitrogen level, the historical cultivars Libellula, San Pastore and U-1 had a higher protein content (13.1–15.2%) with significantly higher total gliadins, which resulted in a significantly higher gliadin/glutenin ratio (1.68–1.92). In the modern cultivars, protein content varied between 11.4% and 14.6% with a well-balanced gliadin/glutenin ratio (1.08–1.50), except for cultivar MV Nemere which had a high gliadin/glutenin ratio at both nitrogen levels (1.81 vs. 1.87). In summary, increasing nitrogen level enhanced grain protein content while the composition of gliadin and glutenin fractions was changed to a lesser extent and was largely cultivar specific and therefore should be considered for wheat baking quality assessment and breeding purposes.

Mechanochemical activation of gluten network development during dough mixing

The interplay between wheat flour composition and mixing conditions required for achieving gluten network development is addressed here. Dough mixing tests were carried out on a planetary mixer using a wide range of water content (68–125 mL per 100 g of flour), mixing speed (50–110 rpm) and flour types. A model predicting dough development time (ddt) from the specific mixing power input (Pwsp, J.s−1.kg−1) was established, whatever the details of mixing conditions (dough water content, mixing speed or mechanical energy input). It involves two intrinsic flour parameters: flour's energy demand and specific critical power (respectively Ef and Pwsp* with ddt = Ef/[Pwsp- Pwsp*]). Amongst several flour biochemical features, only the proportion in unextractable glutenin polymers in total glutenin polymers (UPP) was found correlated with Ef and Pwsp*. Dough supplementation with thiol/disulfide interfering chemicals, as well as addition of a pause at the beginning of mixing lowered Pwsp*. From the findings of the study, gluten network development is hypothesized to rely on the mechanical activation of “stress bearing” bonds of different nature, namely interchains disulfide- and Hydrogen-bonds.

Changes in Antioxidant System during Grain Development of Wheat (Triticum aestivum L.) and Relationship with Protein Composition under FHB Stress.

Fusarium head blight (FHB) is found in both temperate and semi-tropical regions and causes losses in wheat (Triticum aestivum L.) resulting in reduced yield, deteriorated grain quality, and contamination of the grains with mycotoxins, primarily deoxynivalenol (DON). In this study, we focused on the identification of protein components in Fusarium-inoculated and non-inoculated wheat samples along with the major antioxidant enzymes that Fusarium can encounter during FHB infection process in six winter wheat varieties when FHB symptoms started to occur. Our hypothesis was that wheat antioxidants and H2O2 may play a role against Fusarium infections, consequently preserving protein grain components. Results showed that in more resistant varieties (Olimpija and Vulkan) DON content of inoculated flour was less accumulated and thus the major gluten network was not significantly attacked by Fusarium spp. The maximum increase in guaiacol peroxidase (POD) activity in response to FHB treatment was detected in the FHB-resistant varieties Olimpija and Vulkan, while the lowest increase in H2O2 content was detected in the FHB-susceptible variety Golubica. A particular reduction in the content of both total glutenin and high-molecular-weight glutenin subunits was detected in susceptible wheat varieties after serious artificial infection, along with increased DON accumulation. The defense mechanism in wheat varieties differed, where resistant varieties’ protein composition depended on POD activity as a detoxification agent.

The overexpression of high-molecular-weight glutenin subunit Bx7 improves the dough rheological properties by altering secondary and micro-structures of wheat gluten.

Bread wheat (Triticum aestivum L.) is one of the crucial cereals consumed by human beings and wheat gluten, the natural macromolecules, mainly determines the processing quality of wheat dough. The high-molecular-weight glutenin subunits (HMW-GSs) of gluten proteins are recognized as one of the main components regulating the rheological properties of dough. The overexpressed Bx7 subunit (Bx7OE) has been reported to improve wheat quality and rheological properties of dough, however its effect on secondary and micro- structures of gluten is still unclear. In this study, we evaluated the composition of main storage proteins in wheat grains of two near-isogenic lines and studied the effect of Bx7 subunit expression level on the secondary structures of gluten and micro-structure of gluten during dough mixing process. Results showed the protein content, HMW-GSs proportion in total glutenins and free sulfhydryl content increased in the flour of HMW-Bx7OE wheat line, and the accumulation of unextractable polymeric protein during grain filling stage accelerated. It was found that the content of β-sheets in secondary structures of gluten increased and a more compact micro-structure of gluten network formed in the dough. Protein network analysis characterized and quantified the alterations in the gluten micro-structure. In the process of dough mixing, protein area, total protein length, number of junctions and branching rate reach the peak at dough development time, which was consistent with Chopin mixing profile. Interestingly, during dough mixing, the above-mentioned parameters of HMW-Bx7OE showed less changes than those of HMW-Bx7 wheat line, indicating Bx7OE improved the dough stability during mixing. To conclude, Bx7OE alters the secondary and micro- structures of gluten and thus improves the mixing and rheological properties of wheat dough.

Changes in Protein Composition in the Grain and Malt after Fusarium Infection Dependently of Wheat Resistance.

The grain yield, as well as the quality and safety of the wheat grains and corresponding malt can be compromised by Fusarium spp. infection. The protein content of the grain affects the chemical composition and enzyme levels of the finished malt. The malting industry demands varieties with good malting and brewing performance, as well as good agronomic performance and disease resistance. The best method of disease control is breeding and selection for resistant varieties. Due to higher requirements for malting wheat worldwide, the goal of this investigation was to explore changes in protein distribution in wheat grains and corresponding malt, which are under higher pressure of Fusarium head blight (FHB) infestation in field conditions. The present study provides new knowledge on the impact of the FHB on the distribution of protein components of naturally Fusarium-infected (control) and Fusarium-inoculated wheat varieties in the grain and the corresponding malt in two consecutive years (2015/2016 and 2016/2017). The results showed that Fusarium infection of the susceptible variety Golubica, decreased total glutenins (5.9%), and both high and low molecular weight glutenin subunits (2.5% and 3.5%, respectively) in wheat grains, compared to control, in 2016. In contrast, gliadins and α-gliadins increased significantly (+7.6% and +5.1%, respectively) in the same variety. Wheat grains of the more resistant variety Vulkan showed an increase of the total glutenins content (+4.3%), and of high and of low molecular weight glutenin subunits (+1.2% and +3.2%, respectively) after Fusarium-inoculation, compared to naturally infected grains in 2016. Susceptible variety Golubica increased total glutenins (+9.1%), and both high and low molecular weight glutenin subunits (+3.5% and +5.6%, respectively) after Fusarium-inoculation in wheat malt, compared to naturally infected malt in 2016. In 2017, when disease pressure was higher than in 2016, there was a tendency in all varieties to increase gliadins and its sub fractions after malting, and to decrease glutenins and its sub fractions in Fusarium-inoculated treatment. In conclusion, FHB dramatically depressed grain yield (up to 37%) and quality (glutenins and high molecular weight subunits) in the susceptible Fusarium variety, which makes it inconvenient for malting.

Effect of Climate Change on Wheat Quality and HMW Glutenin Subunit Composition in the Pannonian Plain

The primary goal of this study is to improve our understanding of the extent of influence of climatic factors in Serbia and high‐molecular‐weight glutenin subunit (HMW‐GS) composition upon wheat end‐use quality. In‐depth analyses were performed on four bread wheat cultivars that are the most common in agricultural practice in Serbia. Total glutenin content showed significant difference between the production years, in opposition to gliadins. Cluster analysis of different percentages of glutenin and gliadin subunit molecular weight ranges (<40,000, 40,000–80,000, 81,000–120,000, and >120,000) indicated that the year of production and the cultivar did not have a significant effect on the percentage ranges for glutenins. However, they had a considerable impact on the percentage ranges for gliadins. Production year and the interaction of year and cultivar had the strongest influences on the percentage of SDS‐unextractable polymeric proteins. A synergistic effect of the HMW‐GS composition and climatic conditions revealed that all eight samples with HMW‐GS composition 2*, 5 + 10, 7 + 9 along with the highest Glu 1 score of 9 (out of a maximum of 10) produced in the year 2011 belonged to two clusters with the best wheat end‐use quality. Furthermore, the climate conditions in 2011 made it possible for the wheat cultivars with HMW‐GS composition –, 2 + 12, 7 + 9 to possess similar qualities as cultivars with HMW‐GS composition 2*, 5 + 10, 7 + 9 produced in 2012.

Impact of Fusarium spp. infection of bread wheat ( Triticum aestivum L.) on composition and quality of flour in association with EU maximum level for deoxynivalenol

Contamination of grain with mycotoxins such as deoxynivalenol (DON) is the major threat after Fusarium head blight (FHB) infection of wheat, however technological quality can also be impaired. The European Union has established maximum levels (ML) of DON for wheat grain and foodstuffs. The composition (starch, gluten proteins) and quality (protein content, sedimentation value, wet gluten, water absorption, mixing properties of dough, baking volume) of 72 flour Type 550 samples from two years either fulfilling or exceeding ML of 0.75 mg kg-1 were investigated. DO content of flours ranged widely from below limit of quantification to 11.84 mg kg-1. Aside from a slight loss of loaf shape in flours highly exceeding ML, no negative effect on composition and quality of flour was observed in flours exceeding ML compared to those fulfilling ML. A significant decrease in total glutenin and LMW-GS content did not correlate with any quality trait. Hence, if flours fulfill ML for DON, reduced technological quality due to FHB is not significant.

The influence ofFusariuminfection on wheat (Triticum aestivumL.) proteins distribution and baking quality

Under artificial Fusarium infection the total glutenin content determined by chromatographic (RP-HPLC) method was significantly reduced in comparison to gliadins which were increased. Among protein types, α-GLI and HMW-GS were the highest affected. Artificial Fusarium infection significantly increased GLI/GLU ratio when compared with the natural infected samples. Artificial Fusarium infection dramatically decreased the dough mixing tolerance and had a considerable negative effect on dough energy, maximum resistance, and resistance/extensibility ratio. Disturbed GLI/GLU ratio and an increased amount of mycotoxin DON under artificial Fusarium infection showed a strong negative impact on affected functional properties of dough and bread. Total and γ-GLI as well as GLI/GLU ratio were significantly positively affected by mycotoxin DON in contrast to total GLU, HMW-GS and LMW-GS which were negatively affected. Results indicated that the stability of baking quality parameters of cultivars more tolerance to the Fusarium infection can be well define by lower accumulation of mycotoxin DON.

DISTRIBUTION OF WHEAT PROTEIN COMPONENTS UNDER DIFFERENT GENETIC BACKGROUNDS AND ENVIRONMENTS

The crude protein and protein components of fourteen commercial bread wheat cultivars grown in Eastern Croatia over two years and three locations were evaluated. Protein components were measured by reversed phase – high pressure liquid chromatography. A dominant effect of genotypes was obtained for the proportion of albumins and globulins, γ- gliadins and total glutenins, while year had a more pronounced impact on crude protein, total gliadins and high molecular weights and low molecular weights glutenin subunits. Locations had the strongest influence on total extracted proteins. Variability of gliadins to glutenins ratio was at the same extent influenced by the genotype and the year. Among interactions, genotype x year and year x location had the highest impact on evaluated proteins. The principal component analysis showed that wheat cultivars were differentiated according to variability of grain protein components. Considering the significant impact of proteins on the wheat bread-making quality, cultivar classification by protein components significantly contributes to the improvement of breeding program towards the creation of high quality cultivars. Keywords: wheat, protein components, environments, RP-HPLC

Split Application of Potassium Improves Yield and End‐Use Quality of Winter Wheat

Many studies have investigated the effects of basal K fertilization on the yield and quality of wheat (Triticum aestivum L.). However, less is known about the influence of the split application of K on yield, size distribution of protein fractions, and quality of wheat. Field studies were conducted in two successive seasons (2010/2011 and 2011/2012) using four winter wheat cultivars, Jimai 20, Gaocheng 8901, Yannong 19, and Jinan 17, and three regimes of K fertilization (K0: no K fertilization; KB: basal K fertilization of 120 kg ha−1; KS: basal K fertilization of 60 kg ha−1 plus topdressing of 60 kg ha−1 at jointing). The yield and its components, protein composition, dough‐mixing properties, and bread‐making quality were determined after harvesting. On average, the KS treatments had a yield advantage over KB treatments mainly resulting from higher kernel weight. The KS treatments improved wheat quality resulted in increased glutenin/gliadin ratio, higher polymerization index (the ratio of sodium dodecyl sulfate to insoluble glutenin in total glutenin), and larger glutenin macropolymer (GMP) particles compared to KB fertilization. No differences in the content of crude protein and wet gluten were found between the KS and KB treatments. Dough development time, stability time, and loaf volume were positively correlated with the glutenin/gliadin ratio, polymerization index, and average size of the GMP, respectively. These results suggest that KS can improve the yield and end‐use quality of winter wheat.

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.

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.

Grain quality characteristics of spring wheat (Triticum aestivum) as affected by free-air CO2 enrichment

Spring wheat (Triticum aestivum L. cv. Triso) was grown in a free-air carbon dioxide (CO2) enrichment (FACE) system at Stuttgart–Hohenheim (Germany) in 2008 to examine effects on crop yield and grain quality. Elevated CO2 had no significant impacts on aboveground biomass and grain yield components except for an increase in thousand grain weight by 5.4% with size distribution shifted towards larger grains. Total grain protein concentration decreased by 7.9% under CO2 enrichment, and protein composition was altered. Total gliadins and their single types (ω5-gliadins, ω1,2-gliadins, α-gliadins, and γ-gliadins) were reduced, while albumins/globulins, total glutenins and their subunits were not influenced. The gluten proteins (gliadins plus glutenins) were lowered by 11.3% in the high-CO2 treatment, whereas proportions of gluten protein types were slightly affected as only ω1,2-gliadins decreased. Accordingly, all proteinogenic amino acids were decreased by 4.2 to 7.9% in concentrations per unit flour mass, although partly below the level of statistical significance. In contrast, the composition of amino acids on a per protein basis remained unaffected except for a decline in serine. Among the minerals, the concentrations of calcium, magnesium, iron and cobalt decreased, while an increase was observed for boron. The concentrations of total non-structural carbohydrates and starch decreased, whereas fructose, raffinose and fructan increased. Total lipid concentration remained unaffected by the CO2 enrichment, whereas the grain carbon/nitrogen relation was increased by 8.5%. Implications may occur for consumer nutrition and health, and for industrial processing, thus breeding of new wheat cultivars that exploit CO2 fertilisation and maintain grain quality properties is regarded as one potential option to assure the supply chain for the future.

Quantitation of LMW‐GS to HMW‐GS Ratio in Wheat Flours

ABSTRACTA comparison was made of methods for measuring the LMW/HMW glutenin subunit (GS) ratio for glutenin. A set of near‐isogenic wheat lines with the number of HMW‐GS varying from 0 to 5 was utilized to provide a wide range of LMW/HMW‐GS. Glutenin preparations were obtained from ground whole meal after solubilization of monomeric proteins by dimethyl sulfoxide (DMSO) or 50% propanol or by fraction collection from a preparative SE‐HPLC column. Analyses were made on the reduced glutenin from each of the three preparations by RP‐HPLC, SE‐HPLC, and SDS‐PAGE. Both solvents, DMSO and 50% propanol, extracted appreciable amounts of polymeric protein, thus casting some doubts on the accuracy of the determinations. This problem was largely avoided when the polymeric fraction was collected from the eluate of a total glutenin extract run on a preparative SE‐HPLC column. Less glutenin was removed by the two solvents for lines with a greater number of HMW‐GS or with strength‐associated HMW‐GS 5+10 coded by the 1D chromosome. Collection of the polymeric protein in SE‐HPLC, followed by separation of the glutenin subunits in RP‐HPLC, was the best method for quantitating the LMW/HMW‐GS ratio. SE‐HPLC gave a clear separation of the two groups of subunits as well as HMW albumins. RP‐HPLC has the potential advantage of being able to quantitate individual subunits.

Coupling effects of irrigation and nitrogen fertilization on grain protein and starch quality of strong-gluten winter wheat

Effects of irrigation and nitrogen fertilization on the grain yield, protein composition, protein quality, starch composition and starch pasting properties of a strong-gluten winter wheat were investigated in a high fertility field. Compared with non-irrigation treatment, grain yields under irrigation treatments were significantly increased, but the content of grain protein, monomeric protein and flour wet gluten was reduced. There were no significant differences in the above parameters between the irrigation treatments. Nitrogen application could significantly increase grain yield under low irrigation frequency (W0 and W1), while the neglected effect on yield was observed with high irrigation frequency (W2 and W3). With the increase of irrigation frequency, the glutenin content leveled off, but the changes of glutenin composition were not uniform, in which the soluble glutenin content was increased, while the insoluble glutenin content and polymerization index (the ratio of insoluble glutenin to total glutenin) were reduced. Both dough development time and stability time became shorter with the increased irrigation frequency. Nitrogen application improved the content of all grain protein fractions and grain quality, in which the increased degree in non-gluten protein (albumin and globulin) was higher than gluten protein (gliadin and glutenin), and the increased degree in soluble glutenin was found higher than that of insoluble glutenin. The interactive effects of irrigation and nitrogen on starch composition were significant. Starch content and amylopectin content was increased as irrigation frequency added in non-nitrogen treatment. Compared to non-irrigation treatment, irrigation significantly increased the starch content and the amylopectin content in nitrogen application treatment, but the starch and amylopectin content had no significant difference between irrigation treatments. Amylose content and the ratio of amylose to amylopectin were reduced while RVA indexes (peak viscosity, breakdown, final viscosity and setback) were increased as irrigation frequency was increased. Nitrogen application significantly improved the amylopectin content and decreased the amylose content in lower frequency irrigation, while the amylopectin content was decreased and the amylose content was enhanced by nitrogen application in higher frequency irrigations.

A method of extraction and separation of wheat gluten

After removing gliadin and other proteins with 7.5% 2-propanol and 0.3 mol/L NaI, the total glutenin subunits were extracted with two kinds of buffer, one containing 25% 2-propanol, 0.04 mol/L Tris-HCI (pH=8.0), 10% SDS and 2% DDT and the other containing 25% 2-propanol, 0.04 mol/L Tris-HCI (pH=8.0), 10% SDS and 1.4% VP. In SDS-PAGE electrophoresis (4% stacking gel and 13% resolving ge1) system HMW-GS and LMW-GS were clearly separated by the improved method with only a single step. The background of the SDS-PAGE gel was gliadin-free. It was more effective and applicable to separate and distinguish the complex LMW-GS. This method will be used in wheat protein separation, variety identification and improvement.

Effects of different Lactobacillus and Enterococcus strains and chemical acidification regarding degradation of gluten proteins during sourdough fermentation

Dough quality and baking performance of wheat dough are significantly affected by the qualitative and quantitative composition of the gluten. Therefore, the degradation was studied of specific fractions of gluten proteins in sourdough as affected by starter cultures. Doughs were fermented for 0, 5, and 24 h at 30 °C after addition of Lactobacillus sakei, L. plantarum, L. sanfranciscensis or Enterococcus faecalis. Chemically acidified doughs were used as controls. All doughs were analyzed quantitatively for their content of albumins, globulins, gliadins, glutenins, and glutenin macropolymer by means of a combined extraction/HPLC procedure. Protein degradation during sourdough fermentation was primarily due to acidic proteases present in flour. While L. sakei, L. plantarum and L. sanfranciscensis were mostly non-proteolytic, E. faecalis clearly contributed to gluten proteolysis. Single gluten protein types were clearly different in their resistance to proteolytic activities of the dough system and E. faecalis, and, in contrast to total glutenins, the amounts of gluten macropolymer were significantly reduced already after 5 h of incubation. When longer fermentation times were applied, gluten was substantially degraded. The strongest decrease was found for the glutenin fraction leading to an increase of alcohol soluble oligomeric proteins in the gliadin fraction. The extent of the decrease of monomeric gliadins was strongest for the γ-type followed by the α- and the ω-types. This indicates that dough properties residing in specific types of gluten fractions can be influenced by the duration of fermentation and the application of proteolytic strains.