Morphologies and microstructures of cornstarches with different amylose–amylopectin ratios studied by confocal laser scanning microscope

The morphologies and microstructures of cornstarches with different amylose–amylopectin ratios (waxy: 0/100; maize: 23/77; Gelose 50: 50/50; and Gelose 80: 80/20) were studied by a confocal laser scanning microscope (CLSM). The temperature-induced changes of the cornstarch granules in excess of water were also studied under CLSM. Acid hybridization of starch by HCl was used to enhance the difference between amorphous and crystalline ranges. It was found that the high-amylose starches (G50 and G80) were brighter than those of low-amylopectin starches (waxy and maize) under confocal laser light, and the average (decreasing) fluorescence intensity sequence of the granules was G80 > G50 > maize > waxy. Waxy and maize starches showed clear internal cavities and channels, whilst G50 and G80 had bright cores. Sharp growth ring structures can be clearly observed for low-amylose starches (waxy and maize) after acid hydrolysis. Gelatinization of all starches starts at the hilum and the adjacent of the channels, and spreads rapidly to the periphery. This work is the first time that three-dimensional images of partly gelatinized granules have been constructed and presented from different confocal images, which allows further exploration of the mechanisms of gelatinization.     

小麦冷源功能叶片的显微结构和气体交换特性

小麦冷源具有明显降低小麦体温的作用,是培育冷型小麦的优质种质资源。论文通过常规石蜡切片的方法观察比较了冷源、冷型小麦小偃6号和暖型小麦9430功能叶片的显微结构,并在灌浆结实期测定了功能叶片的叶绿素含量、净光合速率、蒸腾速率和气孔导度,旨在揭示冷源功能叶片的结构和生理特性。结果表明,冷源旗叶叶片厚度分别比冷型小麦和暖型小麦高出19.3%和9.0%,倒二叶分别高出19.7%和5.7%,倒三叶分别高出37.2%和2.7%;冷源旗叶叶脉横截面积分别比冷型小麦和暖型小麦高出25.2%和37.7%,倒二叶分别高出5.9%和12.6%,倒三叶分别高出13.1%和33.3%;冷源旗叶、倒二叶和倒三叶中的叶脉间距分别比冷型小麦小偃6号同叶位功能叶片高出17.7%,2.0%和9.2%,分别比暖型小麦9430同叶位功能叶片低3.7%、6.8%和8.3%。随着籽粒灌浆的进行,冷源、冷型小麦和暖型小麦功能叶片的叶绿素含量、净光合速率、蒸腾速率和气孔导度均呈下降趋势,但冷源和冷型小麦在灌浆前、中、后期均较暖型小麦高,功能叶片衰老缓慢,功能期较长。     

钎焊热循环对白口铸铁组织和性能影响的研究

利用高频感应加热炉,通过改变钎焊温度,钎焊时间和冷却速度,研究了白口铸铁的组织和性能变化规律,钎焊温度和时间对组织和硬度影响不大,冷却速度对组织影响也不明显,但冷却速度提高时,硬度提高,达到ＨＲＣ６４．５。白口铸铁钎焊易形成溶蚀缺陷,温度和时间对白口铸铁钎焊溶蚀非常敏感,严格控制钎焊温度和时间是获得优质钎缝的保证。     

环境条件对乳清蛋白凝胶特性和微观结构的影响

 【目的】研究离子种类、离子强度、加热温度、pH、蛋白浓度等条件对乳清蛋白凝胶的质地性质、持水性、微观结构的影响。【方法】利用质构仪测定添加不同浓度的NaCl和CaCl2对所形成的乳清蛋白凝胶硬度、弹性、内聚性的影响,利用扫描电镜观察凝胶微观结构。【结果】盐对凝胶性质影响很大,相同条件下钠盐形成凝胶需较高浓度且弹性和持水性好于钙盐凝胶;蛋白浓度达到8%～10%时凝胶质地较好。在微观结构上钠盐凝胶比钙盐凝胶内部更加致密结实。这在宏观上表现为钠盐凝胶硬度相对较大,持水性更好。【结论】钠盐凝胶具有更好的凝胶质地和功能性质。     

结缕草种子(颖果)解除休眠前后的颖显微结构

对解除休眠前的结缕草种子通过扫描电镜观察,发现颖结构致密,其上覆盖一层脂类物质。在平行的颖脊上有整齐排列的颖孔,这些颖孔均被Si质的颖孔盖所覆盖。经过处理,解除休眠后,脂类物质及颖孔盖脱落,颖孔被打开,构成颖的纤维网络清晰可见,种子内外的水、气交换可顺利进行,减少胚生长的阻力,发芽率达到潜在生活力水平。经过牛胃消化排出的结缕草种子,颖结构的形态变化及发芽率与人工处理的结果基本相同。     

蓝霜狐不同生长期皮肤组织超微结构观察

用扫描电镜和透射电镜观察蓝霜狐１日龄、４５日龄、１２０日龄、２１０日龄各期皮肤的胶原纤维、弹性纤维、网状纤维的结构变化。结果表明：胶原纤维随日龄增加变粗大且成束,明暗周期横纹清晰;弹性纤维随日龄增加而减少;网状纤维随日龄增加而增多,排列更加密集,交织成网。由胎皮到冬皮的组织结构变化,影响其质量变化。成熟冬皮具强的抗张性能,具好的柔性和韧性。另外,还观察了皮肤中的皮脂腺、竖毛肌、微血管及皮下脂肪层在不同日龄的变化。     

野牦牛和家养牦牛牛毛的扫描电子显微镜观察

应用扫描电子显微镜对野牦牛和家牦牛胸部、腹部、背部牛毛的鳞片花纹类型及分布、鳞片间距、毛细度等特征进行研究。结果表明,家牦牛和野牦牛牛毛的显微结构在扫描电子显微镜视野下存在一定差异,3个部位中,相对规则波浪形鳞片长度占毛总长比例家牦牛小于野牦牛;单回纹形鳞片长度占毛总长比例家牦牛大于野牦牛;毛鳞片间距家牦牛略高于野牦牛;毛最粗处直径平均值野牦牛整体大于家牦牛,以上分析表明家牦牛和野牦牛的毛可为2者鉴定提供依据。     

The effect of sodium chloride on gluten network formation and rheology

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.     

Effects of vacuum mixing and mixing time on the processing quality of noodle dough with high oat flour content

The effects of different mixing parameters (vacuum mixing and mixing time) on oat (70% oat flour) and wheat noodle dough were investigated on the basis of textural properties and gluten formation. The results showed that at a vacuum degree of −0.06 MPa and mixing time of 10 min, oat and wheat dough sheets exhibited the highest resistance to extension and glutenin macropolymer (GMP) content, and had the most compact and uniform gluten network. Compared with wheat noodle dough, oat dough had lower resistance to extension, lower tightly bound water content, and higher GMP content. Microstructural examination showed that oat noodle dough had a more aggregated distribution of gluten protein compared with wheat noodle dough under the optimum mixing parameters. Furthermore, the poor binding ability of vital wheat gluten with water molecules caused the indexes of oat noodle dough to be more strongly affected by the changes in mixing parameters than wheat noodle dough.