The influence of drought and heat stress on the expression of end-use quality parameters of common wheat

The effects of drought and heat stress on quality parameters of wheat (Triticum aestivum) cultivars were studied under field conditions in a 2-year trial (2009–2010) in northwest Mexico. Under no stress conditions, rapid small-scale parameters [protein (GP; FP) content, SDS sedimentation (SDSS), mixograph peak time (MPT), swelling index of glutenin (SIG), and lactic acid retention capacity (LARC)] showed significant relationship with gluten strength (alveograph energy, W) and bread loaf volume (LV). SIG and LARC were better than SDSS and MPT for predicting W, while SDSS was better than W and SIG for predicting bread LV. Most quality traits were primarily controlled by genotype (G), although environment (E) and G × E also had significant effects. Heat and drought stress showed contrasting effects on LARC, MPT, alveograph parameters [tenacity (P), extensibility (L), P/L ratio, W] and LV. Increase in P and decrease in L resulted in higher tenacity (larger P/L), which may explain the smaller loaf volume under drought stress. In contrast, decrease in P and increase in L, may explain the improved bread volume observed under heat stress. It is advisable to select for wheat quality under both favorable and abiotic stress conditions to identify genotypes with quality stability across environments.     

人工饲养条件下喜马拉雅旱獭血脂和血液流变学指标测定

测定人工饲养条件下喜马拉雅旱獭血脂及血液流变学指标,并对雌雄个体间及与野生状态下喜马拉雅旱獭相关指标进行比较。结果表明:人工饲养喜马拉雅旱獭雌、雄性个体全血黏度(ηa)、全血还原黏度(ηn)、红细胞压积(HCT)、红细胞刚性指数(IR)及血沉方程K值(KESR)差异均不显著(P0.05);野生状态与人工饲养条件下的旱獭血液流变学和血脂水平比较显示,野生成体旱獭血浆黏度(ηp)、红细胞沉降率(ESR)、全血还原黏度(ηn)、红细胞电泳指数(ES)、胆固醇水平(CHOL)、甘油三酯(TG)水平均显著高于人工条件下驯养旱獭的指标(p0.01)。以上数据的获得将为喜马拉雅旱獭作为实验动物进行应用开发提供基础资料。     

2种糊化方式对小麦面粉流变及回生特性影响的比较

对传统加热糊化和微波糊化小麦面浆的过程进行了比较。在相同反应温度与时间的条件下,分别考察体系的糊化特性、流变学特性、贮藏回生特性及其回生后的超微结构。结果表明：小麦面粉经微波糊化后体系均匀、黏度较大、剪切恢复性小、超微结构致密,传统加热糊化不充分、体系黏度较低、存在剪切恢复性、超微结构不均匀;微波糊化只能在短时间内延缓淀粉体系的回生作用,不能降低其最终回生度。     

超声波一步法制备纤维素氯化锂/二甲基乙酰胺溶液

运用超声波一步法制备了纤维素氯化锂/二甲基乙酰胺的离子溶液。通过调节超声波功率和处理时间,对纤维素、氯化锂和二甲基乙酰胺混合物超声波处理5~7 min,并于室温下搅拌3~5 h,即可获得纤维素均匀溶液;研究了超声波处理对纤维素分子及形态结构的影响,并对纤维素溶液的流变性能进行了考察。结果表明,超声波一步法具有工艺简单、易操作以及溶解时间短的特点,所得到的纤维素溶液具有高分子溶液的一般特征。     

Characterization of two 1D-encoded ω-gliadin subunits closely related to dough strength and pan bread-making quality in common wheat (Triticum aestivum L.)

Gliadin proteins of 113 common or bread wheat (Triticum aestivum L.) cultivars and advanced lines from China and other countries, were analyzed by high performance capillary electrophoresis (HPCE) and reversed-phase high performance liquid chromatography (RP-HPLC). A major protein peak migrating at 3 min by HPCE and eluting at about 20 min by RP-HPLC was identified in the ω-gliadin region. It was present in cultivars with good pan bread-making quality, whereas most cultivars with poor bread-making quality lacked this protein peak. Quality testing and statistical analysis showed that this ω-gliadin peak was significantly related to dough strength, loaf volume and loaf score. It was separated into two apparent protein components by one-dimensional SDS-PAGE and two-dimensional electrophoresis (2-DE). According to their relative mobilities on the gels, the proteins were designated ω-15 and ω-16, and their accurate molecular masses (42590.5 Da for ω-15 and 41684.1 Da for ω-16) were determined by MALDI-TOF-MS. The ω-15 and ω-16 gliadins possessed the N-terminal amino acid sequences of ARELNPSNKELQQQQ and KELQSPQQQF, and therefore they belonged to 1D-encoded ω-2 type and ω-1 type gliadins, respectively. Both gliadin subunits were always present together among the 86 cultivars analyzed, suggesting that they were encoded by two closely linked genes at Gli-D1 locus. The accumulative characteristics of gliadins during grain development indicated possible additive quantitative effects of ω-15+16 on dough strength. The ω-15 and ω-16 gliadins could be used as valuable genetic markers for wheat quality improvement.     

Measurement of dough specific volume in chemically leavened dough systems

Gas production and gas retention properties of doughs are pivotal to the manufacture of bread of good quality, but these properties are rarely measured directly in fermenting dough due to a paucity of suitable instrumentation. A digital image analysis-based method was used to measure the dynamic specific volume (DSV) of various chemically leavened dough systems. Sodium bicarbonate (1.4–4.2 g per 100 g of flour) in combination with equivalent neutralizing amounts of the leavening acidulants glucono-delta-lactone, potassium acid tartrate, adipic acid or sodium acid pyrophosphate consistently increased the specific volume of bread dough so that void fractions in the dough spanned between 5 and 67% at ordinary fermentation temperatures. The relationship between the specific volume of dough at the end of fermentation and the actual gas evolved (measured independently) was essentially linear and was characterized by a slope that provided a good index of the actual gas-trapping properties of dough. Therefore, the use of the DSV technique in conjunction with chemical leaveners offers the possibility of obtaining quantitative, real time information on the gassing capacity of the leavening system and the gas-holding capacity of the dough.     

兰州拉面专用粉对小麦品质的要求 Ⅰ. 拉面食用评价与小麦粉常规品质的关系

用72个小麦品种(系)研究了面粉品质与兰州拉面品质之间的关系。结果表明，小麦粉蛋白质含量、湿面筋含量、SDS沉淀值都与拉面评分呈极显著正相关，相关系数分别为0.61、0.50和0.60。面团流变学特性中的面团筋力（W）、弹性指数（I.e.）、膨胀指数（G）、面团弹性（L）、面团韧性（P）与拉面最终评分呈极显著正相关，其中W值与     

木材的化学流变学——基础构筑及研究现状

为了使国内木材科学界对木材的化学流变学的基础理论及其研究概况有一个比较全面的了解,作者在归纳了作为建立木材的化学流变学基础的、关于变形和流动一般理论的基础上,就Stein 和Tobolsky基于高分子构造变化与应力松弛之间的对应关系,关于物理流变学和化学流变学的分类,化学流变学研究与其他方法的不同之处,Tobolsky等关于不连续应力松弛测定方法等内容做了比较详细系统的介绍.最后,以几个代表性研究为主干内容介绍了有关木材的化学应力松弛、化学蠕变等化学流变学的研究现状.     

河北省小麦面粉色泽状况研究

以2009年河北省主推小麦品种(粮补品种)为试材,系统研究了河北省推广小麦品种面粉的色泽状况,分析了各小麦品种在面粉及其加工成生面片、熟面片的L*值、a*值、b*值情况,并进行相关性分析。结果表明:河北省小麦面粉样品的L*值平均值为95.76,a*值平均值为0.56,b*值平均值为8.79;加工成生面片后样品的L*值下降,a*值和b*值均有所上升;面片熟制后样品的L*值、a*值和b*值较生面片整体下降,但与面粉相比,制成熟面片后样品的L*值和a*值整体下降,b*值略有上升。河北省小麦面粉色泽在红—绿方向上均略偏向红色,在黄—蓝方向上均偏向黄色。同时指出,各小麦品种的面粉及加工成生面片、熟面片的L*值、a*值、b*值之间存在差异,其中面粉的b*值与其色泽相关性最大。     

A phenomenological analysis of wheat gluten viscoelastic response in retardation and in dynamic experiments over a large time scale

Dynamic measurements and retardation tests (creep and creep recovery) were combined systematically to characterise the different aspects of gluten rheology. Gluten flow behaviour exhibits extreme shear thinning and time-dependent viscosity. The viscoelastic contribution to the total strain behaves linearly over large strain and stress ranges; however, the material shows physical ageing and does not exhibit time translational invariance. In spite of these difficulties, it was possible, in the case of fresh gluten samples or after the material has been submitted to mechanical loading for a period long enough, to obtain the linear viscoelastic response over seven logarithmic decades of time or frequency by combining the data from dynamic measurements and from retardation tests. The method of Kaschta was used to calculate the discrete retardation spectrum from creep recovery data; the spectrum was then used to convert recovery data into storage and loss compliance and modulus. Converted recovery data match dynamic data satisfactorily in the case of fresh gluten. Some discrepancy was observed in the case of gluten submitted to previous mechanical history; it has been attributed to the effect of physical ageing. The storage and nonviscous loss compliance functions show that the extension of the viscoelastic plateau of gluten is very large. Their shape suggests a bimodal spectrum; however, this point would need further confirmation.