基于压痕加载曲线的谷物籽粒物理特性试验与仿真

利用CMT8102微机控制材料试验机对豌豆、玉米、小麦、绿豆进行了加载-卸载试验,得到了4种谷物籽粒的载荷-压痕深度曲线.在谷物籽粒弹塑性力学性能研究中引入Venkatesh反向运算法则,计算出了4种谷物籽粒的弹性模量、屈服应力、硬化指数、接触刚度、最大接触面积等力学特性参数;把得到的弹性模量、屈服应力理论值添加到Abaqus的材料属性模块,对4种谷物籽粒的压入过程进行模拟仿真,得到了压痕形貌图和仿真曲线.仿真和试验曲线拟合结果说明了仿真的有效性,并且验证了Venkatesh反向运算法则在谷物籽粒材料特性研究中的准确性;压痕形貌图说明谷物籽粒具有弹塑性.研究还表明谷物籽粒硬度与应变硬化指数、最大等效接触应力、残余应力和屈服应力呈正比,与应力集中区域呈反比.     

小麦品种籽粒硬度测定方法比较研究

为了找到更好的小麦籽粒硬度测定方法，采用近红外法(NIR)和单籽粒谷物特性测定仪法(SKCS)对54个小麦品种(系)的籽粒硬度进行了测定，并对这两种方法进行了比较分析。结果表明，NIR法和SKCS法测得的籽粒硬度具有较高的相关性(r=0．8727^**)，线性回归方程为YNIR．H=0．2478XSKCS.H 39．666(NIR-H表示NIR法测得的籽粒硬度，SKCS-H表示SKCS法测得的籽粒硬度)；与NIR法相比，SKCS法无需磨粉处理，能较好地反映出样品的均匀性和混杂程度，是一种重复性和稳定性好、快速有效的籽粒硬度测定方法。     

小麦籽粒发育时期Puroindolines蛋白与硬度的关系

为探讨Puroindolines蛋白的表达特点与籽粒硬度的关系,采用改进的SDS-PAGE凝胶分析了不同硬度小麦品种的籽粒在各个发育时期Puroindolines蛋白的表达.结果表明,不同硬度的小麦籽粒中总Puroindolines(PinA和PinB)蛋白的表达量差异不大,但与胚乳淀粉颗粒结合的Puroindolines蛋白量差异非常明显:在籽粒发育的不同时期,软质小麦籽粒淀粉粒表面结合的Puroindolines蛋白量显著高于硬质小麦;基因型同为野生型但硬度有差异的品种,籽粒较软的材料其淀粉粒表面结合的Puroindolines蛋白量也明显高于较硬的材料,说明该蛋白的结合特性是决定籽粒硬度的直接原因.结果还表明,胚乳中水溶性戊聚糖与籽粒硬度关系密切.     

小麦单籽粒性状与品质的关系

目前测定小麦单籽粒品质的方法有单籽粒谷物品质测定法和谷蛋白溶涨指数法(SIG)。为了揭示单籽粒品质检测的作用,选用16个小麦品种(系)进行单籽粒性状的研究,结果表明,品种内单籽粒硬度、籽粒直径、单籽粒重量及SIG的变异较大,水分含量变异不大。单籽粒品质指标硬度、粒重、粒径及SIG与磨粉品质、面团流变学特性、蛋白质品质、籽粒品质部分指标呈显著或极显著相关,这些指标对于预测磨粉品质、早代株系品质筛选及食品品质具有快速、方法简单及预测能力强的优点。将单籽粒谷物品质测定参数及SIG相结合,可以有效地进行小麦育种后代筛选及品质预测。     

大麦籽粒不同部位黄酮含量的比较分析

为了解大麦成熟籽粒中黄酮化合物的分布情况,以来源于5个不同地域的21个大麦品种(系)为材料,采用硝酸铝比色法对大麦籽粒的胚、胚乳和皮层中的黄酮含量进行了测定。结果表明,胚中的黄酮含量最高,胚乳中次之,皮层中最低;但从不同部位的黄酮积累量占籽粒中黄酮总积累量的百分比来看,大麦籽粒黄酮的89.35%来自胚乳,来自胚和皮层的均只占到5%左右。此外,不同来源地对胚中的黄酮含量影响极显著(P0.01),对胚乳和皮层中的黄酮含量也有显著影响(P0.05)。     

小麦籽粒硬度研究进展

小麦籽粒硬度是当前小麦育种的主要目标之一,对小麦的制粉品质有重要影响,是小麦品质评价的重要指标之一。本文从小麦籽粒硬度测定方法、籽粒硬度与胚乳结构的关系、籽粒硬度对面粉品质和面制品品质的影响、籽粒硬度的遗传规律、品种与环境对籽粒硬度的影响、籽粒硬度育种改良等方面介绍了国内外相关领域的研究现状,并对未来发展提出展望,为小麦育种中籽粒硬度的改良提供参考。     

青海小麦籽粒硬度等位变异研究

为了解小麦品种籽粒硬度的遗传多样性,利用单粒谷物硬度测定、PCR扩增和核苷酸测序技术,分析了66份青海小麦品种籽粒硬度主效基因的等位变异。结果表明,青海小麦以硬质类型为主,比例达到47.0%,混合麦比例为19.7%,软质麦比例为33.3%。硬度基因有5种组合类型:野生型、Pina-D1a/PinbD1b、Pina-D1a/Pinb-D1c、Pina-D1a/Pinb-D1x和Pina-D1b/Pinb-D1a。野生型小麦类型比例最高,占59.09%,SKCS硬度指数平均为44.12,变化范围为12.75~84.89。突变类型的品种籽粒均为硬质。因此,在青海硬质小麦可以通过突变类型的分子标记进行选育,软质小麦选育需在利用硬度基因分子标记筛选的基础上进一步考察籽粒硬度性状的表现型。     

喷施6BA和ABA对冬小麦籽粒胚乳细胞增殖和淀粉积累的影响

为给植物生长调节剂的合理使用提供依据,在田间试验条件下,以小麦品种济南17和鲁麦21为试验材料,在小麦抽穗期喷施6-苄基腺嘌呤(6BA),开花期喷施脱落酸(ABA),研究其对小麦胚乳细胞增殖动态及淀粉积累、组分的影响.结果表明,喷施6BA能显著提高小麦籽粒的胚乳细胞数、胚乳细胞分裂中后期的增殖速率、粒重和淀粉积累量,且可降低小麦强势籽粒淀粉直/支比例,有利于淀粉品质的改善;但对弱势籽粒中的淀粉直/支比例没有显著的影响.喷施ABA能降低胚乳细胞分裂中后期的增殖速率,显著减少强势籽粒的胚乳细胞数,但对弱势籽粒的胚乳细胞数和粒重没有显著影响,对淀粉直/支比例的影响也不明显.2种外源激素处理都没有改变小麦籽粒的穗粒数和总淀粉含量,表明小麦粒重的变化可能主要是由胚乳细胞的增殖造成的.     

小麦品种偃展4110低能离子束突变体库的初步建立及籽粒硬度突变体筛选

低能离子束注入技术是近年发展起来的一种物理性诱发突变技术,在作物诱变育种中应用越来越广泛。为进一步探讨低能离子束的诱变功效,构建小麦突变体库,采用两种不同剂量的低能氮离子束对软质小麦品种偃展4110进行了诱变处理,共获得了1 024份M2代单株。随机选取其中600份材料,采用单籽粒谷物特性测试仪(SKCS)进行籽粒硬度测定。结果表明,共有31份突变体为混合麦,3份突变体为硬质麦,突变率为5.7%。采用Ha(Hardness)位点Puroindoline基因不同区段的特异引物对14份突变材料进行扩增后发现,有3份材料的Ha(Hardness)位点包含至少一个大的片段缺失,导致小麦胚乳质地变硬。本试验利用低能离子束技术成功构建了一个小麦品种偃展4110的突变体库,可为小麦功能基因组学研究提供重要的材料支持。     

山西小麦品种籽粒硬度与主要品质性状研究

为明确山西省近十年育成小麦新品种的籽粒硬度和品质状况,利用单籽粒谷物特性测定仪(SKCS)、DA7200多功能近红外分析仪,对来自山西省近十年审定的56个小麦新品种的籽粒硬度、蛋白质含量、出粉率等指标进行了检测和分析。结果发现,山西省近十年审定的小麦品种中,硬质麦比例较高,为78%,混合型麦和软质麦比例较低,分别为12%和8%;硬度指数范围较宽,为16.33～78.93。经相关分析,小麦籽粒硬度指数与被测品质性状均呈正相关关系,其中,与出粉率、吸水率、最大拉伸阻力均呈极显著正相关(P0.01)。硬质麦的蛋白质含量、湿面筋含量、出粉率、沉降值等品质参数均显著高于混合型麦和软质麦。混合型麦的蛋白质含量、湿面筋含量、出粉率、沉降值等品质参数略高于软质麦。     

Evaluation of Tissue Dissociation of Durum Wheat Grain (Triticum durum Desf.) Generated by the Milling Process

The three major botanical components (starchy endosperm, aleurone layer and pericarp) of eight durum wheat samples exhibited significantly different compositions and concentrations in phenolic acids. The starchy endosperm, the aleurone layer and the pericarp were respectively characterised by a low content in ferulic acid (FA), a high content intrans -sinapic acid (t -SA), and a high content in ferulic acid dehydrodimers (DHD). These three chemical markers can be exploited to differentiate the three grain botanical parts within milling fractions and to evaluate the milling efficiency, particularly the separation between bran and endosperm. The histological dissociation of the wheat grain generated by the milling process can be investigated further into details using the three phenolic acids markers. A separability index (S i) was proposed in order to quantify the ease of dissociation of endosperm from bran. Differences in S i values between wheat varieties grown under various agricultural conditions demonstrated the relevant variability of this character. The structural and molecular factors implied in the control of tissue dissociation are discussed in details.     

Biochemical markers: Efficient tools for the assessment of wheat grain tissue proportions in milling fractions

To produce safe and healthy whole wheat food products, various grain or bran dry fractionation processes have been developed recently. In order to control the quality of the products and to adapt these processes, it is important to be able to monitor the grain tissue proportions in the different milling fractions produced. Accordingly, a quantitative method based on biochemical markers has been developed for the assessment of grain tissue proportions in grain fractions. Grain tissues that were quantified were the outer pericarp, an intermediate layer (including the outer pericarp, the testa and the hyaline layer), the aleurone cell walls, the aleurone cell contents, the endosperm and the germ, for two grain cultivars (Tiger and Crousty). Grain tissues were dissected by hand and analysed. Biochemical markers chosen were ferulic acid trimer, alkylresorcinols, para-coumaric acid, phytic acid, starch and wheat germ agglutinin, for outer pericarp, intermediate layer, aleurone cell walls, aleurone cell contents, endosperm and germ respectively. The results of tissue quantification by hand dissection and by calculation were compared and the sensitivity of the method was regarded as good (mean relative errors of 4% and 8% for Crousty and Tiger outer layers respectively). The impact of the analytical variability (maximum 13% relative error on coarse bran) was also regarded as acceptable. Wheat germ agglutinin seems to be a promising marker of wheat germ: even if the quantification method was not able to quantify the germ proportions in milling fractions, it was able to classify these fractions according to their germ content. The efficiency of this method was tested, by assessing the grain tissue proportions of fractions exhibiting very different compositions such as flour, bran and aleurone-rich fractions obtained from three different grain or bran dry fractionation processes (conventional milling, debranning process, production of aleurone-rich fractions from coarse bran). By calculation of the composition of the different products generated, it was possible to study the distribution of the different tissues among fractions resulting from the different fractionation processes. This quantitative method is thus a useful tool for the monitoring and improvement of processes, and allows the effects of these processes to be understood and their adaption to reach the objectives.     

Enzymatic modification and particle size reduction of wheat bran improves the mechanical properties and structure of bran-enriched expanded extrudates

The aim of this study was to examine enzymatic modification of wheat bran, performed in a low-moisture process, and the reduction of bran particle size as means of improving the technological performance of wheat bran in expanded extrudates. Modification of bran by hydrolytic enzymes increased the crispiness and decreased the hardness and piece density of extrudates containing wheat bran and endosperm rye flour in 20:80 ratio. These improvements correlated (P < 0.01 or 0.05) with an increased content of water extractable arabinoxylan and decreased water holding capacity of the bran, as well as with increased longitudinal expansion of the extrudates. Furthermore, bran with a fine average particle size (84 μm) produced extrudates with improved mechanical properties and higher radial expansion than coarse bran (particle size 702 μm). The impact of bran particle size was also observed in the cellular structure of the extrudates as differences in cell size and homogeneity. The bran drying method, oven or freeze drying after enzymatic modification, did not have a major impact on the properties of the extrudates. The study showed that the functionality of wheat bran in extrusion can be improved by enzymatic modification using a low-water process and by reduction of bran particle size.     

Identification and quantification of phenolic acids and anthocyanins as antioxidants in bran,embryo and endosperm of white,red and black rice kernels (Oryza sativa L.)

Whole rice grain comprising endosperm, embryo (or germ), and bran has potential beneficial health effects in addition to provision of nutrients. The distribution of phenolic acids and anthocyanins in endosperm, embryo, and bran of white, red, and black rice grains was investigated in this study. The total phenolic content (TPC) was highest in the bran, averaging 7.35 mg GAE/g and contributing 60%, 86% and 84% of phenolics in white, red and black rice. The average TPC of the embryo and endosperm were 2.79 and 0.11 mg GAE/g accounting for 17% and 23%, 4% and 10% and 7% and 9% in white, red and black rice, respectively. The antioxidant capacity determined using DPPH and ORAC displayed a trend similar to TPC. Free/conjugated phenolic acids in white, red and black rice bran accounted for 41%, 65% and 85% of total acids. Bound phenolic acids in rice bran accounted for 90% of total acids in whole grain. Cis-p-coumaric was detected in bound form in bran while cis-sinapic acid was detected in the free/conjugated form in embryo and bran. Cyanidin-3-O-glucoside and peonidin-3-O-glucoside were identified mainly in black rice bran as the total anthocyanins. Cyanindin-3-O-rutinoside was also detected in black rice bran.     

Rheological Behaviour of Wheat Endosperm—Proposal for Classification Basedon the Rheological Characteristics of EndospermTest Samples

A simple, rapid method for the preparation of parallelepiped-shaped samples from a grain is used in the proposal of a study of the rheological behaviour of wheat endosperm. Compression rupture, creep and relaxation tests are used. A series of compression tests on mealy and vitreous endosperm of different wheat varieties (soft, hard and durum) shows that the rheological properties are influenced by both the genetic origin and grain vitreousness. The main mechanical characteristics—Young's modulus, elastic and rupture stresses, rupture energy and rupture strain—were determined at moisture contents of 12 to 17%. The influence of the moisture content on rheological behaviour is demonstrated. The vitreous endosperm of some wheat varieties displays considerable ductility before rupture. The nature of this plasticity was analysed by creep and relaxation tests on hard and soft wheats. Comparison of the different endosperm rheology values clarifies the notions of vitreousness and hardness. Wheat classification based on endosperm mechanical characteristics is proposed. It seems that Young's modulus characterises hardness whereas rupture energy is related to the vitreousness of the different varieties studied. Entering the results in a Young's modulus–rupture energy system leads to a classification of wheats according to two essential factors: hardness of varietal origin and vitreousness of cultural origin.     

紫糯小麦籽粒石蜡切片制作技术优化及淀粉粒累积分析

为了探明糯性小麦授粉后籽粒淀粉粒的累积情况,以山农紫糯2号授粉后不同天数的籽粒为试验材料,通过对传统石蜡切片技术的脱水、透明和浸蜡等环节进行改进,制作切片后对小麦籽粒结构发育进行观察研究。结果显示,与传统石蜡切片方法相比较,技术改良70%乙醇和无水乙醇脱水时间与逐级透明和渐进式浸蜡环节后,小麦籽粒（授粉后0~14 d）不皱缩变形,石蜡切片完整,且染色分明,结构显示清晰。授粉后0~2 d,果皮中已经开始积累少量淀粉粒,随着授粉后天数推移而逐渐增多;授粉后第6天,胚乳内部逐渐由游离核期向细胞化过渡;授粉后第8天,胚乳细胞进一步增大,淀粉粒开始累积,但体积较小;授粉后第10~12天,胚乳细胞向无核化发展,不同部位胚乳细胞和淀粉粒的排列分布呈现明显差异;授粉后第14天,胚乳细胞中几乎完全充满淀粉粒。表明改进的石蜡切片制作方法适合于早期小麦籽粒的结构研究。     

Effect of different soaking conditions on inhibitory factors and bioaccessibility of iron and zinc in pearl millet

Pearl millet was decorticated to obtain a bran rich and endosperm rich fraction. The two fractions were soaked in solutions with varying pH. Pearl millet grains were germinated and steamed followed by decortication to obtain two fractions. It was observed that bran rich fractions contained high concentrations of iron, zinc, polyphenols, phytic acid, fibre and flavonoids. Soaking for short duration of 3 h did not result in major mineral losses but decreased the inhibitory factors which depended on the pH. Alkaline soaking decreased flavonoid content by 62.7% in the endosperm rich fraction, while acidic soaking decreased phytic acid content to the maximum in the bran rich fraction. Combination of treatments like germination and heat decreased the phytate content to the maximum in the endosperm rich fraction. Acidic conditions improved zinc bioaccessibility in the bran rich fraction (35%) and iron bioaccessibility (2.5%) in the endosperm rich fraction. Bran rich fraction from germinated grain also had enhanced bioaccessibility of both the minerals but comparatively lesser when compared to soaking under acidic conditions. Soaking the grain components under slightly less than neutral conditions also decreased some of the inhibitory factors and improved the zinc bioaccessibility to some extent in the bran rich fraction.     

Assessment of commercial milling potential of hard wheat by measurement of the rheological properties of whole grain

The single-kernel characterisation system (SKCS) 4100 instrument has previously been shown to provide in situ measurements of the rheological properties of the bran and endosperm layers of wheat, otherwise only possible following their isolation by dissection or machining. The current study has confirmed that endosperm maximum stress (endosperm strength (ES) as measured using the SKCS 4100 correlates highly (r=0.898$r=0.898$) with compressive strength (maximum stress, σ_max) measurements performed on specimens of endosperm tissues of known dimensions, isolated from different subsamples of the same bulk wheat samples. This provides a means of scaling the stress axis of the crush–response profile plots to the Instron scale (MPa) so that the SKCS endosperm stress/strain curves for hard wheat, soft wheat and durum can be compared with Instron results presented in the literature. In addition, a simple method for the measurement of ES and stiffness, using the SKCS 4100, has been developed. The method has been shown to rank wheat samples according to their performance when processed on a 650 kg/h pilot mill. The criterion against which the SKCS-derived rankings were compared was the Milling Quality Index, which uses both the percentage flour extraction and Branscan speck count measurements.     

Study of the microstructure of durum wheat endosperm using X-ray micro-computed tomography

Durum wheat grains are used for producing food, such as pasta or couscous. The grain mechanical properties which are linked to its internal micro-structure (i.e. endosperm porosity) are known to determine its ability to produce semolina during milling. The proportion of grains having porous endosperm in a batch appears therefore as a critical quality factor for the durum wheat value chain. Our objective was to investigate the ability of X-ray micro-tomography (μCT) method to describe the porous or vitreous counterpart structures in the endosperm of durum wheat grains. We selected two different durum wheat samples displaying vitreous or partially porous endosperms. The grains were analyzed using μCT at two pixel sizes (1 μm or 7 μm). The μCT data collected at 7 μm pixel size were used for qualitative classification of grains according to apparent distribution curve of the porosity parameters. Analysis of μCT images at 1 μm pixel size allowed us to propose pore size classification in the vitreous and porous parts of the endosperm in three durum wheat grain. Results are used to better describe the durum-wheat endosperm microstructure, but requires long scanning periods.