首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Albumins and globulins were fractionated by coagulation at 70, 100, and 120°C and were studied by microscopic and electrophoretic methods. The coagulated albumins of a U.S. commercial hard red winter (HRW) wheat blend sample included larger aggregates than those of an Israeli spring wheat (SW). Dialyzed globulins appeared as finger-like patterns with embedded oil droplets and heat-coagulated globulins appeared as aggregates with fibril-like patterns. An increase in size of coagulated aggregates was observed as temperatures increased (70, 100, and 120°C). Differences in capillary zone electrophoresis (CZE) and sodium dodecyl sulfate (SDS) – polyacrylamide gel electrophoresis (PAGE) patterns between coagulates from samples of an Israeli SW and a U.S. commercial HRW wheat were seen at all the coagulation temperatures. SDS-PAGE patterns of coagulates obtained at lower temperatures exhibited relatively more intense bands of higher molecular weight components, and those obtained at higher temperatures exhibited relatively more intense bands of lower molecular weights.  相似文献   

2.
The different gluten subunits, gliadins, LMW glutenins, and HMW glutenins have been reported to play different key roles in different type of wheat products. This paper studied the interaction between gliadin, LMW and HMW glutenins in soft, hard and durum semolina flour doughs during different stages of mixing. In order to see how do the gluten subunits (gliadin, LMW glutenin and HMW glutenin) redistribute during mixing, dough samples were taken at maximum strength and 10 min after maximum strength. The doughs have been mixed with the same level of added water (55%), therefore they all have different strengths values due to their changes in proteins content. Oscillatory rheological measurements were performed on the doughs. It has been found that HMW glutenins are relatively immobile because of their less molecular mobility and do no redistribute themselves especially at high strength for doughs such as hard wheat flour. LMW glutenins and gliadins on the other hand redistribute themselves at even at high dough strengths forming a more stable network. In weaker doughs such as soft wheat, the breakdown of the three proteins subunits is responsible for the decay in dough strength. We have also visualized how the greater amount of LMW glutenins in semolina is in constant interaction with HMW glutenins and gliadins allowing the dough to maintain a stable strength for an extended mixing time. Finally, we have found the ‘in situ’ detection and quantitative analysis techniques to be more sensitive to the changes occurring in the gluten network of the dough than the oscillatory rheological analysis.  相似文献   

3.
Aqueous dispersions of gluten (1.6 mg/ml) were heated for varying times at temperatures from 30 to 120 °C and the proteins characterized by size exclusion-high performance liquid chromatography (SE-HPLC) and sodium dodecyl sulphate-polyacrylamide gel electrophoresis. At temperatures below 100 °C at pH 5.0, only increases in the molecular size of the glutenins were observed. At 120 °C, gliadins as well as glutenins polymerized as seen by a progressive shift of the SE-HPLC profile to lower elution times with time of heating. The gliadins appear to cross-link only with glutenins, as no peaks were observed at elution times expected for gliadin oligomers. The changes in the chromatographic profiles were accompanied by increasing amounts of protein becoming unextractable even with sonication. ω-Gliadins did not participate in the changes, suggesting that disulfide bonding was involved. After polymerization at 120 °C, the kinetics of reduction of the protein by mercaptoethanol were monitored by SE-HPLC. The activation energy of the reduction process was calculated to be 35 kJ/mol.  相似文献   

4.
Gliadins were extracted from hard red spring wheat flour with 70% (v/v) aqueous ethanol and lyophilized. These crude gliadins were dissolved in 70% (v/v) aqueous ethanol or 4 mM acetic acid with or without ultrasonication. Precise measurements of the density and ultrasound velocity of the solutions were made at 20 °C. For non-sonicated solutions, crude gliadins solubilized in ethanol had a slightly larger partial specific volume (0.76 cm3 g−1), and a larger partial specific adiabatic compressibility coefficient (15 × 10−11 Pa−1) compared to those solubilized in acid (0.739 cm3 g−1, 3.1 × 10−11 Pa−1, respectively). Larger values are consistent with the existence of complexes formed by gliadins and lipids in aqueous ethanol solutions. Utrasonication had no effect on these protein–lipid complexes based on measurements of density, but it did alter the compressibility of gliadins in dilute acid (making them almost twice as compressible). Novel insights into gluten protein properties can be gained from compressibility measurements of solutions using ultrasonic resonators when coupled with measurements of protein specific volume.  相似文献   

5.
Nitrogen(N),a macronutrient essential for plant growth and development,is needed for biosynthesis of protein and starch,which affect grain yield and quality.Application of high-N fertilizer increases plant growth,grain yield,and flour quality.In this study,we performed the first comparative analysis of gliadin and glutenin subproteomes during kernel development in the elite Chinese wheat cultivar Zhongmai 175 under high-N conditions by reversed-phase ultra-performance liquid chromatography and twodimensional difference gel electrophoresis(2D-DIGE).Application of high-N fertilizer led to significant increases in gluten macropolymer content,total gliadin and glutenin content,and the accumulation of individual storage protein components.Of 126 differentially accumulated proteins(DAPs)induced by high-N conditions,24 gliadins,12 high-molecularweight glutenins,and 27 low-molecular-weight glutenins were significantly upregulated.DAPs during five kernel developmental stages displayed multiple patterns of accumulation.In particular,gliadins and glutenins showed respectively five and six accumulation patterns.The accumulation of storage proteins under high-N conditions may lead to improved dough properties and bread quality.  相似文献   

6.
The sensitivities of flour proteins to precipitation by NaCl at acid pH were investigated by extraction with 0·05macetic acid solution containing varying concentrations of salt and by precipitation of the proteins extractable in acetic acid solution by addition of salt to varying concentrations. Flours of two Canadian hard red spring wheat cultivars (Glenlea and Katepwa) were used because of their different dough strengths. Electrophoresis results showed that as the NaCl concentration was raised, higherMrproteins of gliadins and glutenins were less extractable and were more easily precipitated. This tendency was more evident for the proteins of cv. Glenlea than those of cv. Katepwa, indicating that the former (stronger) is more sensitive to NaCl than the latter. SDS–PAGE results indicated that differences in the molecular size and subunit composition (i.e.relative proportion of high:lowMrglutenin subunits, and relative proportion of x-:y-type highMrglutenin subunits) of glutenin polymer contribute to differences in NaCl sensitivity. The differences appear to be related to the baking strength of the flour.  相似文献   

7.
This paper reviews our present knowledge of the chromosomal location of the genes that control the synthesis of gliadins and glutenins, the two major groups of storage protein in the endosperm of wheat (Triticum aestivum). Allelic relationships and genetic linkage between genes are also discussed. The areas that require futher investigation are identified.  相似文献   

8.
The effect of salt concentration used in preparing gluten, on the subsequent dissolution of gluten in water, was examined. Flour from a Canadian hard red spring wheat cultivar, Katepwa, was used to prepare glutens using three different solvents, i.e. distilled deionized water (DDW), 0·2% NaCl solution and 2% NaCl solution. The isolated wet glutens were extracted sequentially with DDW, providing four water soluble fractions and an insoluble residue. The amount of protein in each fraction was determined and respective compositions were assessed electrophoretically under reducing and non-reducing conditions. Surprisingly, DDW extracts of gluten prepared with 2% NaCl contained almost all the gliadins, except some ω-gliadin components, and most of the polymeric glutenin. For the gluten prepared with 0·2% NaCl, most of the gliadin, but only a small portion of glutenin, was extracted. For gluten prepared with DDW, only part of the gliadins and almost no glutenin was extractable with water. The DDW solubilities of gluten proteins prepared in DDW, 0·2% NaCl and 2% NaCl were 27, 52, and 85%, respectively, after four sequential extracts with DDW. The large increases in the solubility of gliadin and glutenin proteins in DDW when the gluten is prepared in salt solution (after removal of most of the salt) can be explained on the basis of a salt-induced conformational change of the proteins, which renders water a more effective solvent.  相似文献   

9.
Protein content is well known to affect the functional properties of processed wheat products. Traditionally performed on aliquots (0·25–2·2 g) from samples ranging in size from 30–40 g (for combustion and Kjeldahl analyses) to several hundred grams (for whole-grain near-infrared analysis), these methods inherently do not provide information on single-kernel protein variability. Inspection procedures by the United States Department of Agriculture for grading and classification of wheat are undergoing change to provide the processor or end user with information on the variability of several single-kernel properties including hardness, moisture, weight, and wheat class. The present study has focused on demonstrating the feasibility of measuring crude protein content of single wheat kernels by near-infrared reflectance. More than 300 commercial wheat samples from the 1992 U.S. harvest, representing five (hard red winter, hard red spring, soft red winter, hard white, and soft white) of the six (durum excluded) market classes were chosen, from which 10 kernels were randomly selected and handled on a single-kernel basis. Handling consisted of reflectance scanning (1100–2498 nm), drying (for moisture compensation), and combustion (for reference protein-content determination). Partial least squares and multiple linear regression models, when applied to samples excluded from calibration, demonstrated standard errors of performance ranging from 0·462 to 0·720% protein depending on the modeling technique, number of classes used to develop the model, and the wheat class tested. The pooling of wheat classes to produce a general model did not diminish model accuracy. Best results were achieved with an 1100–1400-nm region. Model performance worsened as the wavelength region widened or as the minimum wavelength shifted from 1100 nm to higher values.  相似文献   

10.
Starch was isolated from 98 hard red winter (HRW) wheat and 99 hard red spring (HRS) wheats. Granule size/volume distributions of the isolated starches were analyzed using a laser diffraction particle size analyzer. There were significant differences in the size distribution between HRW and HRS wheats. The B-granules (<10 μm in diameter) occupied volumes in the range 28.5–49.1% (mean, 39.9%) for HRW wheat, while HRS wheat B-granules occupied volumes in the range 37.1–56.2% (mean, 47.3%). The mean granule sizes of the distribution peaks less than 10 μm in diameter also showed a significant difference (HRW, 4.32 vs. HRS, 4.49 μm), but the mean sizes of the distribution peaks larger than 10 μm were not significantly different (21.54 vs. 21.47 μm). Numerous wheat and flour quality traits also showed significant correlation to starch granule size distributions. Most notably, protein content was inversely correlated with parameters of B-granules. Crumb grain score appeared to be affected by starch granule size distribution, showing significant inverse correlations with B-granules. Furthermore, the linear correlations were improved when the ratio of B-granules to protein content was used, and the polynomial relation was applied. There also appeared to be an optimum range of B-granules for different protein content flour to produce bread with better crumb grain.  相似文献   

11.
李硕碧 《麦类作物学报》2007,27(6):1016-1022
为了更好地理解环境和基因型对小麦阿拉伯木聚糖含量的影响,为小麦品质改良提供科学依据,采用比色法测定了美国西部51个硬质小麦品种的阿拉伯木聚糖组分含量,这些小麦品种包括冬小麦和春小麦,分别被种植在3个不同的地点.结果表明,参试冬小麦品种水溶性和总阿拉伯木聚糖含量的变异范围分别为0.39%～0.81%和3.09%～4.04%,春小麦品种这两种木聚糖含量范围分别为0.48%～0.92%和3.94%～4.70%.小麦籽粒阿拉伯木聚糖含量的变异同时受品种、环境及其互作效应的显著影响,环境效应太于品种效应.小麦品种间阿拉伯木聚糖含量的变异主要表现在水溶性组分上.就不同组分而言,基因型对水溶性阿拉伯木聚糖组分的影响相对较大,环境则分别对冬小麦水不溶性、春小麦水溶性阿拉伯木聚糖组分有较大的影响.品种间和环境间阿拉伯木聚糖含量的变异,冬小麦大于春小麦;水溶性阿拉伯木聚糖含量的遗传型方差春小麦大于冬小麦.冬、春小麦的水溶性阿拉伯木聚糖含量的广义遗传力均大于95%,通过遗传育种的方法改良小麦阿拉伯木聚糖含量是可行的.冬小麦与春小麦阿拉伯木聚糖含量的平均值之间无明显差异.  相似文献   

12.
Enhancing pasture persistence is crucial to achieve more sustainable grass‐based animal production systems. Although it is known that persistence of perennial ryegrass is based on a high turnover of tillers during late spring and summer, little is known about other forage species, particularly in subtropical climates. To address this question, this study evaluated survival of grazed tall fescue tillers growing in a subtropical climate. We hypothesized that hard tactical grazing during winter to remove reproductive stems (designated as ‘flowering control’), and nitrogen fertilization in spring, would both improve tiller survival over summer, and thus enhance tiller density. This was assessed in two experiments. In both experiments, few tillers appeared during late spring and summer and so tiller density depended on the dynamics of vegetative tillers present in the sward in spring. In Experiment 2, flowering control and nitrogen fertilization both enhanced the survival of that critical tiller cohort, but the effects were not additive. Responses were similar but not statistically significant in Experiment 1, which had a warmer, drier summer and lower overall survival rates. Unlike grasses in temperate environments, persistence of tall fescue in this subtropical site appeared to follow a ‘vegetative pathway’; i.e., new tillers were produced largely in autumn, from vegetative tillers that survived the summer.  相似文献   

13.
Changes of aggregation behavior of wheat gluten during carboxylic acid deamidation upon hydrothermal treatment were investigated to test the influences of deamidation on the aggregation extent of wheat gluten. Hydrothermal treatment induced that the size of soluble wheat gluten aggregate progressively increased by cross-linking of gliadins and slowly cleaved glutenins. But significant changes in molecular weight distribution, solubility under six denaturing agents’ treatment and Zeta potential of wheat gluten aggregates were observed at 6 min heating time and distinct shift of intra-/inter-molecular interactions of wheat gluten aggregates occurred before and after 6 min heating treatment respectively. Moreover, as heating time increased, the island-like aggregates decreased markedly and the striped aggregates increased notably. To explain the aggregation behavior in this case, we postulated that the extent of aggregation of wheat gluten depended on the balance between intra-/inter-molecular electrostatic repulsion, the non-covalent and disulfide bonds formation in the system. Hence, a scheme was drawn, which appeared to be the mechanism responsible for the aggregation of wheat gluten through thermal cross-linking and opening up of the network structure of wheat gluten aggregates by deamidation.  相似文献   

14.
  相似文献   

15.
There is no previously published data covering the viscoelasticity of Osborne protein solubility fractions. Therefore, the objective of this study was to compare the viscoelastic properties of Osborne fractions, water soluble pentosans, flour and bread using relaxation tests. Sintered tablets from glutenins presented similar elasticity as gliadins but almost twice the viscosity. However, most of the wheat viscoelasticity performance in tablets was given by the sum of the non-gluten components (albumins, globulins, residue and especially water soluble pentosans). The residue was 86.1% w/w in flour and contained 4% protein while its estimated viscoelastic effect was higher compared to all the other flour components. Regarding the estimated viscosity in flour due to protein from specific fractions, it was higher in gliadins compared to glutenins. The residue although has low protein in flour (4.0%), the large amount of residue in flour had significant viscoelastic effect. The viscoelasticity of water soluble pentosans corrected by weight was similar to the Osborne protein fractions. The results indicate that the starch, pentosans, and non-gluten components may not be considered merely as inert filler and play a major role in determining the viscoelastic nature of flour and bread.  相似文献   

16.
The objective of this study was to examine the effects of whole-wheat flour (WWF) particle size on the quality attributes of WWF tortillas. WWF samples of different particle size distributions from commercial U.S. hard white (median diameters: 175.7, 128.6, 120.0, 108.5 and 102.4 μm), hard red winter (median diameters: 173.7, 133.6, 124.3, 110.8 and 104.2 μm) and hard red spring (median diameters: 173.7, 132.1, 124.7, 112.9, 106.3 μm) wheat classes were obtained by fine grinding of bran and shorts and re-combining with the rest of fractions. For all three wheat classes, as WWF median particle size decreased, the L* (lightness) value decreased but the adjusted damaged starch, polyphenol oxidase activity, and a* and b* values increased. Mixolab data showed that development time decreased as WWF particle size was reduced, while stability time and starch retrogradation increased. As for WWF tortilla quality, the breaking force and extensibility increased with decreasing particle size from ∼175 to 129–134 μm, but diameter and thickness were not significantly affected. The results indicated that reducing the median particle sizes of WWFs from ∼175 μm to ∼130 μm would significantly improve the WWF tortilla quality.  相似文献   

17.
2006-2014年我国小麦品质在年度和品质区之间的变化   总被引：2，自引：0，他引：2  
为了解我国小麦在年度间和品质区之间的品质变化,对2006-2014年我国10个品质区637个小麦品种6 339份样品的籽粒品质、面粉品质和面团流变学特性进行测定与分析.结果表明,(1)我国小麦籽粒蛋白质含量较高,平均达13.94％,湿面筋平均含量为30.4％;但蛋白质质量一般,沉淀指数平均值为32.1mL,稳定时间平均值为5.8 min,相对美国硬红冬小麦较低.(2)年度间小麦品质呈规律性偏态分布,平均值在年度间变化无规律;从品质类型看,强筋、弱筋小麦比例在减少,中筋小麦比例在增加.(3)品质区之间小麦质量差异较大,东北、北部和西北春麦区、华北北部强筋麦区、黄淮北部强筋与中筋麦区、黄淮南部中筋麦区蛋白质数量性状高于长江中下游中筋与弱筋麦区、四川盆地中筋与弱筋麦区和云贵高原麦区;蛋白质质量性状表现较为复杂,其中长江中下游中筋与弱筋麦区小麦稳定时间一般,但最大拉伸阻力较高,华北北部强筋麦区、黄淮北部强筋与中筋麦区和黄淮南部中筋麦区小麦稳定时间较高,但最大拉伸阻力一般;各品质区以中筋小麦为主.我国小麦总体质量表现为中等水平.小麦品种类型结构的变化是导致年度间小麦质量以及品质区小麦质量变化的重要原因,北方强筋麦区优质强筋小麦品种和南方弱筋麦区优质弱筋小麦品种减少,反映了强调产量、大力推广高产品种的生产实际情况.  相似文献   

18.
To overcome the cost and expense of milling and baking hundreds of samples in wheat breeding programs, cereal chemists have developed various rapid predictive tests for end-use quality assessment. In this study, five small-scale rapid tests, including Solvent Retention Capacity (SRC) and Swelling Index of Glutenin (SIG), were compared for viability and accuracy to determine end-use quality using small quantities of flour. The tests were applied on commercial hard red spring and hard red winter wheat cultivars from two of the three main production regions in South Africa. Rheological and bread-baking characteristics were related to results of the rapid tests. Highly significant cultivar differences were seen for all rheological and baking-related characteristics, and SRC and SIG parameters, with a strong genotype effect. The environment effect was also highly significant across regions, especially for flour protein content (FPC), which affected the rheological and baking-related characteristics differently across the regions. Correlations among SRC, SIG, rheological, and baking quality-related parameters were highly significant, but inconsistent for the two production regions. Only lactic acid SRC and SIG correlated consistently with the rheological and baking quality-related characteristics in both production regions.  相似文献   

19.
  相似文献   

20.
为了解新疆小麦品种籽粒硬度概况和puroindoline基因等位变异类型及其分布,以121份新疆冬、春小麦品种(包括51份农家品种和70份育成品种)为材料,采用单粒谷物特性测试仪(SKCS)和分子标记技术,对其SKCS硬度及puroindoline基因型进行了测试和鉴定。结果表明,新疆小麦硬度变化范围较大,以硬质麦为主,占61.2%。冬性农家品种籽粒硬度高于春性农家品种,冬、春小麦育成品种籽粒硬度基本相同(60.6和60.8)。新疆小麦puroindoline基因的类型丰富,共检测到野生型(Pinb-D1 a)、Pina-D1 b、Pinb-D1 b、Pinb-D1 p、Pinb-D1 ab和Pinb-D1 ac6种类型。硬质麦以Pina-D1 b、Pinb-D1 p、Pinb-D1 b3种突变类型为主,其频率分别为33.8%、31.1%和28.4%。冬性农家品种含有3种类型,以Pina-D1 a/Pinb-D1 b类型居多,春性农家品种含有4种类型,以野生型(Pina-D1 a/Pinb-D1 a)为主,冬、春麦育成品种含有4种常见类型,其中冬麦以Pinb-D1 b类型为主,其频率为39.5%,春麦以Pina-D1 b(PINA缺失)类型为主,其频率为59.4%。另外,冬性农家品种中有4个品种属于Pina-D1 a/Pinb-D1 ab类型,春性农家品种中有1个品种属于Pina-D1 a/Pinb-D1 ac类型,均属硬质麦的稀有突变类型。不同puroindoline基因型的籽粒硬度大小也存在差异,其中Pinb-D1 ab突变型的硬度值最高,Pinb-D1 a最低,并且Pina-D1 b、Pinb-D1 b和Pinb-D1 p3种硬质类型的籽粒硬度没有显著性差异。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号