Effects of gamma-irradiation of wheat on gluten proteins     

H. Köksel  H.D. Sapirstein  S. Çelik  W. Bushuk 《Journal of Cereal Science》1998,28(3):243-250

The effects of ⁶⁰Co gamma-irradiation treatments (2·5, 5·0, 10·0 and 20·0 kGy) on the gluten proteins of two bread wheats and one durum wheat cultivar were investigated. Dough rheological properties of the flour processed from the irradiated wheat were also determined using a computerised micromixograph. Irradiation caused a significant deteriorating effect on all mixogram parameters. There was no observable effect of irradiation on gliadin proteins analysed by polyacrylamide gel electrophoresis. The 50% 1-propanol-insoluble (50 PI) glutenin fraction was highly affected by irradiation. By sodium dodecyl sulfate polyacrylamide gel electrophoresis, reduced 50 PI glutenin showed a noticeable reduction in band intensities of both high (HMW) and low molecular weight (LMW) glutenin subunits (GS) with increasing irradiation dosage greater than 5 kGy. The irradiation effect on 50 PI glutenin was further studied and quantified by reversed-phase high-performance liquid chromatography of glutenin subunits; there was a progressive decrease in the quantity of subunits with increasing irradiation dose level. Compared to non-irradiated wheat, the relative decline in total insoluble glutenin at the 20 kGy dosage level ranged from 34–49% depending on cultivar. Increasing levels of irradiation also progressively reduced the ratio of HMW:LMW-GS up to 13–15% at 20 kGy indicating that irradiation had a greater effect on the largest polymers of glutenin. The observed weakening of dough mixing properties and concomitant decline in the quantity of 50 PI glutenin with increasing levels of gamma-irradiation are consistent with a degradation of glutenin to a lower average molecular size by depolymerisation and/or disaggregation.  相似文献   

Rheological Properties of Dough During Mechanical Dough Development   总被引：1，自引：0，他引：1  

H. Zheng  M. P. Morgenstern  O. H. Campanella  N. G. Larsen 《Journal of Cereal Science》2000,32(3):293

During mechanical development dough is subjected to both shear and extensional deformations. Thus, it is expected that both flow conditions contribute to the development of dough. In order to monitor rheological changes, occurring during mixing, shear and extensional properties of dough prepared with two flours of different strength and various levels of mixing energy were determined using fundamental rheological methods. Rheological measurements included: small deformation and large deformation (shear test), planar extensional flow and a combined shear/extensional flow test, namely extrusion test. Results obtained in this research showed that, during mixing, dough develops with an increase in both apparent shear and extensional viscosities. For all the tests, plots of the measured rheological properties as a function of the mixing energy resembled typical mixing curves. This indicated that the increase in the power drawn by the mixer motor is due to the increase in both apparent shear and extensional viscosities. After peak dough development these properties decreased synchronously with the mixing curves. Results from small deformation shear tests exhibited large variability, particularly when non-mixed and underdeveloped doughs were tested. This variability was associated with poor water distribution in the sample due to insufficient mixing. Results of large deformation tests, including shear, planar extensional flow and the extrusion test, were less variable and showed that mixing and type of flour affect the rheological properties of dough.  相似文献   

低酰基结冷胶/酪蛋白酸钠复合体系液-固转变流变学表征     

陈青  马慧婷  陆海霞  姚兰英 《农业机械学报》2017,48(8):322-327

采用流变学方法研究了低酰基结冷胶(LA)和酪蛋白酸钠(SC)复合体系的液-固转变,对比了储能模量、损耗模量交点法和Winter准则,并利用非等温动力学模型研究了LA/SC复合体系的结构变化。结果表明,Winter准则更适用于表征LA/SC复合体系的液-固转变。对于LA/SC复合体系而言,酪蛋白酸钠存在一个临界质量浓度0.005 g/mL,当体系内酪蛋白酸钠质量浓度低于该临界值时,酪蛋白的添加对凝胶温度影响不大,但当酪蛋白酸钠质量浓度超过该临界值时,酪蛋白酸钠的添加会显著地降低复合体系的凝胶温度。复合体系的松弛指数随着酪蛋白浓度的升高呈先增大后降低的变化趋势,而分形维数则随着酪蛋白浓度的升高呈先减小后增大的变化趋势。非等温动力学研究结果表明,复合体系的凝胶可以分为2个阶段。  相似文献   

超声波处理木薯淀粉对其流变特性的影响   总被引：1，自引：0，他引：1  

陈洁  郭泽镔  刘贵珍  郑宝东 《福建农林大学学报(自然科学版)》2013,42(1)

研究了不同功率(120、180、240 W)超声波处理对木薯淀粉流变特性的影响.动态流变特性研究结果表明,木薯淀粉的贮能模量和损耗模量随着超声波功率的增强而增大,表现出较强的弹性特征;静态流变特性研究结果表明,原淀粉及不同功率超声波处理后的淀粉均属于典型的非牛顿流体,具有假塑性流体特征.在相同的剪切速率下,淀粉糊的表观粘度随着超声波功率的增强而增大,在超声波处理前后均存在剪切稀化现象,具有明显的触变性.在剪切结构恢复力试验中发现各组淀粉的剪切结构恢复力随着超声波功率的增强而明显下降.  相似文献   

The effect of sodium chloride on gluten network formation and rheology     

H.C.D. Tuhumury  D.M. Small  L. Day 《Journal of Cereal Science》2014

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

碎玉米秸秆卷压过程的流变行为试验   总被引：11，自引：10，他引：1  

李汝莘  耿爱军  赵何  包伟  范修文 《农业工程学报》2012,28(18):30-35

为青贮圆捆打捆机的设计和工艺提供基础的力学数据,需要探明碎玉米秸秆卷压过程的流变规律,在分析卷压成型原理的基础上,搭建了碎玉米秸秆卷压试验台,对碎玉米秸秆进行了卷压试验和应力松弛试验。研究了卷压过程中碎玉米秸秆的流变学特征,采用线性黏弹性理论,构建了伯格斯模型,用残数法对应力松弛曲线进行拟合,获得了应力松弛模型及其参数,计算其决定系数。利用相关公式求解,进一步得到伯格斯模型中的黏弹性参数E1=18.33kPa、k1=994.81kPa、E2=27.64kPa、k2=2342.49kPa。由于黏性系数远大于弹性模量,可以初步判断碎玉米秸秆卷压过程的流变行为偏向于流体,这对于深入研究碎玉米秸秆的卷压工艺,实现工艺和装备的优化设计,具有积极作用。  相似文献   

中草药复合制剂对热应激仔猪血液流变学指标的影响     

彭晓清  刘凤华  颜培实 《家畜生态》2013,(12):37-40,57

研究利用人工气候仓模拟热应激环境,建立热应激仔猪模型。试验以64头2月龄中国试验用小型猪为研究对象,将其随机分为对照组、高温应激组、中草药复方提取物工治疗组和中草药复方提取物Ⅱ治疗组,通过Wintrobe测试分析红细胞压积,同时采用血液流变自动分析系统分析全血黏度等血液流变学参数,以期研究中草药复合提取物对热应激仔猪血液流变学指标影响的动态变化。结果显示：应激组仔猪全血黏度高切变率值在第10天显著高于对照组（P〈0．05）,红细胞变形指数在第6天和第10天显著低于对照组（P〈0．05）,红细胞压积在第1、3、6、10天均显著高于对照组（P〈0．05）。治疗组添加中草药提取物复合制剂后,血液流变学指标得到了明显恢复,尤其在热应激的第10天疗效果最明显（P〈0．05）。试验结果说明,热应激刺激对仔猪健康有显著影响,中草药提取复合物可以降低这种热应激产生的生理损伤,其中中草药提取复合物Ⅱ效果优于中草药提取复合物Ⅰ。  相似文献   

Composition and surface properties of dough liquor   总被引：1，自引：0，他引：1  

L.J. Salt  P.J. Wilde  D. Georget  N. Wellner  P.K. Skeggs  E.N.C. Mills   《Journal of Cereal Science》2006,43(3):284-292

The composition and surface properties of dough liquor isolated by ultracentrifugation have been characterised. Addition of ascorbate had no effect and salts only a limited effect, on the yield, protein content and composition of the dough liquor. Fourier transform infrared spectroscopy (FT-IR) revealed the presence of proteins, lipids, starch oligosaccharides together with the non-starch polysaccharide, arabinoxylan. At high dilution the dough liquor air:water interface was dominated by protein, with surface tensions of around 55 mN/m and high surface elasticity. As the concentration was increased, surface tensions dropped to around 40 mN/m for undiluted dough liquor. This was accompanied by the interface becoming less elastic, and indicated that dough liquor lipids were interacting and disrupting the protein films in concentrated dough liquor. Dough liquors from de-fatted flours remained elastic and gave surface tension values of around 50–55 mN/m even at low dilution, indicating that removal of the lipids gave rise to a purely protein stabilised interface. Addition of salt to the dough had the greatest effect on the surface properties, both reducing surface tension and reducing surface elasticity, probably because the charge screening effect of the salt improved the dispersion of lipids in the dough liquor, thus enabling it to disrupt the protein films more effectively. These results indicate that the aqueous phase of bread doughs lining the gas cells would give rise to a mixed protein:lipid interface. Such interfaces are unstable, and would contribute to the instability of the foam structure of risen dough. In addition they show that dough ingredients may modify gas cell stability (and hence may affect crumb structure), by altering the composition and properties of the aqueous phase of doughs.  相似文献   

Effect of arabinoxylans and laccase on batter rheology and quality of yeast-leavened gluten-free breads     

《Journal of Cereal Science》2017

The supplementation effects of maize fiber arabinoxylans (MFAX, 0%–6%), laccase (0–2 U/g flour) and water absorption level (90%–100%) on gluten-free (GF) batter rheology and bread quality were analyzed. From viscoamylograph analysis, lower starch amount in GF flour due to MFAX addition decreased peak viscosity and retrogradation. Surface response plots showed that laccase did not have significant effect on GF batter rheology and bread quality, whilst water was the most important variable. Higher levels of water absorption benefited bread texture. Higher water level (>100 mL/100 g flour) was needed in the experimental design to evaluate correctly the effect of 6% MFAX replacement on GF bread quality. Further analyses were carried in order to adjust water absorption of batters according to their consistency index (K ≈ 100 Pa sⁿ), resulting an optimal water absorptions of 95%, 100% and 105% for control flour and flours supplemented with 3% or 6% MFAX, respectively. Thus, MFAX addition enhanced water-binding capacity of flour and yielded GF breads with higher specific volume and softer crumb texture. These quality parameters were best rated with 6% MFAX addition to flours. This research demonstrated the potential of MFAX to develop GF breads with improved quality, when optimal water level is used.  相似文献   

Genotype × environment interactions and QTL clusters underlying dough rheology traits in Triticum aestivum L.     

《Journal of Cereal Science》2015

Genetic dissection of dough rheology traits (DRT) in hexaploid wheat was carried out using nine mixograph characters evaluated in two consecutive years in three agro-climatic zones in India in an RIL population (HI977 × HD2329). Pearson correlations determined in each year-location indicated 15 stable trait inter-relationships among them but inconsistent correlations with loaf volume (LV) were observed. Using AMMI analysis we derived patterns in G × E interactions (GEI) indicating 6–47% contribution for the DRT. Composite interval mapping using a linkage map of 202 SSR markers identified 144 DRT QTLs of which, 96 were detected in single- and the rest in two to five year-locations. Sixteen QTL clusters located on ten chromosomes were identified and only three of them on chromosomes 1B, 5B and 6D involved LV QTLs. For each trait, majority of the DRT QTLs detected in single as well as multiple environments showed location-specificity and suggested that owing to GEI, breeding for wheat dough quality might need careful selection of QTLs targeted for individual agro-climatic zones. The inconsistent correlations of DRT and LV and differential locations of their QTLs in this population corroborated that using dough rheological traits alone to predict LV might pose challenges during wheat improvement.  相似文献