Effects of endosperm texture and cooking conditions on the in vitro starch digestibility of sorghum and maize flours

The effects of endosperm vitreousness, cooking time and temperature on sorghum and maize starch digestion in vitro were studied using floury and vitreous endosperm flours. Starch digestion was significantly higher in floury sorghum endosperm than vitreous endosperm, but similar floury and vitreous endosperm of maize. Cooking with 2-mercaptoethanol increased starch digestion in both sorghum and maize, but more with sorghum, and more with vitreous endosperm flours. Increasing cooking time progressively reduced starch digestion in vitreous sorghum endosperm but improved digestibility in the other flours. Pressure-cooking increased starch digestion in all flours, but markedly more in vitreous sorghum flour; probably through physical disruption of the protein matrix enveloping the starch. Irrespective of vitreousness or cooking condition, the alpha-amylase kinetic constant (k) for both sorghum and maize flours remained similar, indicating that differences in their starch digestion were due to factors extrinsic to the starches. SDS-PAGE indicated that the higher proportion of disulphide bond-cross-linked prolamin proteins and more extensive polymerisation of the prolamins on cooking, resulting in polymers of M_r>100k, were responsible for the lower starch digestibility of the vitreous sorghum endosperm flour.     

Elucidation of maize endosperm starch granule channel proteins and evidence for plastoskeletal structures in maize endosperm amyloplasts

Previously, starch granules of maize (Zea mays), sorghum (Sorghum bicolor), and millet (Pennisetum americanum) were found to contain channels connecting the interior cavity with the outside surface, and the channels of maize starch channels were found to contain, presumably to be lined with, proteins. One objective of this study was to identify and characterize channel proteins of maize starch granules. A putative starch granule channel protein extract was subjected to 2D-PAGE. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry was used to identify the proteins. Data analysis indicated the presence of actin-like and tubulin-like (FtsZ) proteins, ADP-glucose pyrophosphorylase large and small subunits (Shrunken2 [Sh2] and Brittle2 [Bt2], respectively), granule-bound starch synthase (GBSS), and Brittle1 (Bt1, an adenylate translocator). A combination of Western blot analysis and immunolocalization confirmed the presence of an actin-like protein within the starch granule structure. Another objective was to determine the origin of maize starch granule channels. TEM examination of maize endosperm amyloplasts that did not contain a formed starch granule revealed structures that were connected to the amyloplast membrane and extended inward to the center of the plastid.     

Biochemical characterization of QTLs associated with endosperm modification in quality protein maize

Genetic analysis using quality protein maize (QPM) recombinant inbred lines derived from K0326Y QPM and W64Ao2 identified three quantitative trait loci (QTL) in bins 1.06, 7.02 and 9.03 associated with opaque2 endosperm modification. We evaluated the effects of these QTLs on protein accumulation and starch physicochemical properties. The QTL in bin 1.06 is close to α-zein genes, and vitreous individuals with this QTL had increased accumulation of 19-kDa α-zein, 27-kDa γ-zein and legumin-1. The QTL in bin 7.02 corresponds to the γ-zein locus, and greater accumulation of this protein was found in vitreous individuals. The QTL in bin 9.03 is close to starch biosynthetic genes; greater accumulation of granule-bound starch synthase and amylose was observed in vitreous kernel samples with this locus and that in bin 1.06, as well as less gelatinization enthalpy and crystallinity. Vitreous kernels contained angular-shaped/compact starch granules and more short-intermediate length chains of amylopectin. These results support that endosperm modification in QPM is associated with increased accumulation of γ-zein and other storage proteins, but also show that synthesis of less crystalline starch with more amorphous regions at the periphery of granules, which favor their packing and association with endosperm proteins, may also be an important factor.     

The composition of floury and vitreous endosperm affects starch digestibility kinetics of the whole maize kernel

Maize grain starch is the major energy source in animal nutrition, and its high digestion and utilization largely depend on endosperm traits and the structure of the starch-lipoprotein matrix. The aim of this work was to determine floury and vitreous endosperm traits and its relation to starch digestibility rate. In total, kernels of 30 hybrids were manually dissected, and amylose, total zein and starch and non-starch lipids were determined in both vitreous and floury endosperm. Starch digestibility of the whole kernel was determined based on glucose released during a two-step in vitro pig model of enzymatic digestion, and starch digestibility rate was calculated according to the first-order kinetics. The vitreous endosperm of tested hybrids had higher contents of amylose (204.6 vs 190.4 g/kg), zein (63.2 vs 40.4 k/kg) and starch lipids (5.6 vs 4.9 g/kg), and lower content of non-starch lipids (7.3 vs 9.6 g/kg) than floury endosperm. Digestibility coefficients varied among hybrids, and starch digestibility rate varied from 0.73 to 1.63 1/h. Lipids in both vitreous and floury endosperm negatively correlated with the most of digestion coefficients, whereas zein correlated in vitreous and amylose in the floury endosperm (P < 0.05). Starch digestibility rate negatively correlated with all traits, except amylose content in vitreous endosperm. As a result, a linear regression model with four variables including contents of zein and starch lipids in vitreous and zein and amylose in floury endosperm can predict more than 65% variability of starch digestibility rate of tested hybrids.     

Effect of accelerated aging on maize, sorghum, and sorghum meal

Accelerated aging at 50 °C significantly affected the physical and chemical properties of sorghum and maize. Aging caused associations between starch granules, protein matrix, and cell walls. During aging, floury areas of the endosperm became more corneous; as the endosperm hardened, strong associations between starch and protein developed, causing the endosperm to fracture through endosperm cells instead of along cell walls, which is common for non-aged maize. Aging significantly decreased the pasting viscosity of starch, molecular solubility at 85 °C and the molecular weight of solubilized starch. Solubility of albumins and globulins decreased while solubility of proteins extracted by a reducing agent and/or in alkaline pH increased during aging. Decreased solubility and functionality of starch and protein in aged grain appear to be due to protein oxidation.     

水稻粉质皱缩胚乳突变体fse4的表型分析与基因克隆

【目的】水稻种子主要以淀粉形式储藏能量。淀粉合成需要多种酶类和调控因子参与，机制较为复杂。本研究利用水稻胚乳发育缺陷突变体，克隆和鉴定新的调控淀粉合成相关基因，旨在为研究淀粉合成及其调控提供理论依据。【方法】从化学诱变剂甲基亚硝基脲（1-methyl-1-nitroso-urea, MNU）处理的宁粳3号(Ningjing 3, WT)突变体库中筛选到一个能稳定遗传的胚乳粉质皱缩突变体，命名为fse4 (floury and shrunken 4 )。与籼稻品种Dular杂交获得F1种子（F2），通过图位克隆的策略确定FSE4候选基因。利用杂合植株（FSE4fse4）分离出的粉质种子，观察形态学特征，分析其理化性质。使用扫描电镜和半薄切片技术观察胚乳结构。使用qRT-PCR和免疫印迹分析淀粉合成相关基因表达模式和淀粉合成相关酶类的蛋白积累量。利用全自动氨基酸分析仪测定成熟胚乳各氨基酸含量。【结果】突变体fse4籽粒宽度、厚度以及千粒重显著下降，同时胚乳中总淀粉、总蛋白、直链淀粉含量亦显著下降，而脂肪含量显著上升；淀粉黏度、崩解值和消减值显著低于野生型。突变体fse4中多为单粒型淀粉颗粒，且排列分散。FSE4定位于第5染色体长臂约252 kb的区间内，测序发现编码Δ1-吡咯啉-5-羧酸合成酶基因 （Delta 1-pyrroline-5-carboxylate synthetase, P5CS）第1外显子上发生单碱基替换，导致一保守的氨基酸发生变异。突变体fse4中大部分淀粉合成相关基因表达量下调，多种淀粉合成相关蛋白积累量减少。突变体fse4米粉中多种氨基酸含量发生显著变化，游离氨基酸含量是其野生型的3.6倍。此外，外源喷施脯氨酸能部分恢复突变体fse4种子萌发缺陷表型。【结论】FSE4编码脯氨酸合成关键限速酶P5CS，该基因对胚乳中氨基酸的合成及代谢起重要的调控作用，并影响淀粉的合成与积累。     

Phenotypic Analysis and Gene Cloning of Rice Floury Endosperm Mutant fse4

【Objective】Starch is the main energy reserve of rice endosperm. The biosynthesis of starch is complex, requiring a large number of synthetic enzymes and regulators. Screening rice endosperm defective mutants and cloning the underlying genes will lay theoretical basis for starch biosynthesis and its regulation. 【Method】 A stable genetic floury and shrunken endosperm mutant termed as fse4 (floury and shrunken4) were obtained from the mutant library of Ningjing 3 (WT), which was induced by N-methyl-N-nitrosourea (MNU). An F2 mapping population was generated by crossing the fse4 mutant with Dular (an indica rice variety) and the gene was finally isolated. The floury seeds segregated from the fse4 heterozygous plants were used to observe the morphological features, and the physicochemical properties of the brown rice flour were analyzed. The endosperm structure was observed with a scanning electron microscopy by the semi-thin section technology. The expression of starch synthesis related genes during grain filling was determined by qRT-PCR; Immunoblotting was used to detect the accumulation of proteins related to starch synthesis. The amino acids contents of each mature endosperm were determined with the fully automatic amino acid analyzer.【Result】The 1000-grain weight and grain size were significantly reduced in fse4. Compared with WT, the contents of total starch, amylose and total protein were signi?cantly lower in fse4, while the lipid content was signi?cantly higher. The starch viscosity, breakdown viscosity and setback viscosity of the fse4 mutant were lower than WT. The endosperm of the mutant had many single dispersed starch granules with large spaces between each other. Using 1568 recessive individuals, FSE4 was narrowed down to a 252 kb region. Sequencing revealed a single base substitution in the first exon of the delta 1-pyrroline-5-carboxylate synthetase (P5CS), resulting in a conserved amino acid variation. Most of the genes related to starch synthesis were downregulated in fse4 and the protein accumulation related to starch synthase were reduced. The contents of various amino acids in fse4 rice flour were increased or decreased, the total free amino acids contents in fse4 seeds was 2.6 times higher than those in WT. Exogenous proline was applied during the germination of fse4 seeds, and the embryonic lethal phenotype was partially recovered.【Conclusion】FSE4 encode the key rate-limiting enzyme P5CS of proline synthesis, which plays an important role in the biosynthesis and metabolism of amino acids in endosperm and affects the accumulation of starch.     

Chemical imaging: the distribution of ions and molecules in developing and mature wheat grain

The ability to combine topographical and in situ chemical analysis of individual cereal grains, without recourse to fractionation, offers an opportunity to determine the distribution of functionally- and nutritionally-important components. Three such technologies are reviewed, including immunolocation using monoclonal antibodies specific for different types of wheat prolamins, secondary ion mass spectroscopy (SIMS) to detect the presence of inorganic elements such as sodium and sulphur, and infrared (including Raman and Fourier-transform infrared [FT-IR]) microspectroscopy to determine the distribution of biopolymers across the grain. Immunolabelling has shown that the distribution of prolamin proteins changes across the endosperm, with the outer endosperm containing a much greater proportion of prolamins than the inner endosperm. SIMS has shown, for the first time, the presence of Na⁺ in the phytin granules and that sulphur is enriched at the boundary between the starch granules and the protein matrix. Raman microspectroscopy has been used to investigate the distribution of proteins and the phenolic compound, ferulic acid, across the grain, whilst FT-IR has been used to define the microheterogeneity of arabinoxylans in endosperm cell walls. These methods highlight how in situ analysis can yield new insights into grain composition and how this may be altered by environmental conditions during grain development.     

Effects of Popping on the Endosperm Cell Walls of Sorghum and Maize

The structure of the vitreous endosperm of raw and popped grains of popcorn maize and sorghum has been examined by light and scanning electron microscopy. In both cereals, popping produces everted grains consisting of expanded endosperm foam attached to the pericarp and embryo tissue. As previously reported, each bubble of the foam is formed from an individual starch granule inflated by internal steam pressure. Large fissures may contribute significantly to the expansion of the endosperm foam. The cell walls of the vitreous endosperm of both cereals are shattered into small fragments, which separate slightly as the cell contents expand during popping. Despite this, the endosperm cells retain their polygonal outline. Intact cell walls of raw endosperm, wall fragments from popped endosperm foam, and fragments isolated after treatment of the foam withalpha -amylase, were visualised through the autofluorescence of their ferulic acid content. The in vitro digestibility of popped sorghum was unchanged compared to raw sorghum, whereas that of wet-cooked sorghum was greatly reduced. It is suggested that popping-induced wall fragmentation improves the accessibility of the protein and starch reserves of the endosperm to digestive enzymes.     

Tryptophanyl-tRNA Synthetase Gene WRS1 Regulates Rice Seed Development

【Objective】Aminoacyl-tRNA synthetases (aaRSs) are closely related to the transmission of genetic information. Besides translation, aaRSs in plants participate in gametogenesis and embryo development, early plastid development, immune signal perception and disease defense. In this study, we used a rice endosperm defective mutant to analyze the function of tryptophanyl-tRNA synthase (WRS1) during seed development, proving that WRS1 gene encodes a key factor affecting rice endosperm development. 【Method】In this study, a stably-inherited rice floury endosperm mutant (wrs1) was screened from the mutant library of indica cultivar N22 (Oryza sativa subsp. indica) induced by ethyl methane sulfonate (EMS). Map-based cloning and complementation test identified the target gene. Morphological observation and starch physicochemical properties of wrs1 mature seeds were analyzed. Semi-thin sections were prepared to observe the developing endosperm structure with a scanning electron microscope. qRT-PCR and GUS staining were performed to analyze the expression of WRS1. The expression of starch synthesis related genes in the endosperm at 12 days after flowering was determined by qRT-PCR, and these protein expression levels in mature seed were detected by immunoblotting. The free amino acid contents of mature seeds were measured with a fully automatic amino acid analyzer. 【Result】The seedlings of wrs1 were featured by obvious delay in development and finally withered and died. The floury grains isolated from the heterozygous mutant (WRS1wrs1) showed shrunken belly, decreased grain thickness and thousand-grain weight. Total starch contents, the peak viscosity and breakdown viscosity of pasting starch were lower in wrs1. The compound starch granules in developing endosperm of wrs1 were smaller and loosely arranged. WRS1 was restricted to the 183 kb region of the long arm of chromosome 12. Sequencing revealed a single base substitution in exon 6 of the tryptophanyl-tRNA synthetase gene (WRS1), resulting in a substitution of methionine. The expression of most starch synthesis-related genes in wrs1 was down-regulated, while these proteins showed different accumulation levels. The contents of proteins in wrs1 grains were decreased, while free amino acids contents were significantly increased. 【Conclusion】WRS1 encodes tryptophanyl-tRNA synthase. Mutation of this gene affects amino acid homeostasis and protein synthesis in rice endosperm, resulting in abnormal expression of the genes in starch synthesis pathway which affects starch synthesis and accumulation, and eventually lead to seed development defects.     

Channels within soft wheat starch A- and B-type granules

The nature of channels within wheat starch granules was investigated using scanning electron and confocal laser scanning microscopy. A-type granules stained with 3-(4-carboxybenzoyl)quinoline-2-carboxaldehyde (CBQCA, protein-specific probe) revealed a network of radially oriented, channel-like protein structures similar to those previously reported. However, treatment of the same starch granules with methanolic merbromin (fluorescent dye) solution, which is used to highlight external granule surfaces (including those of channels) under non-swelling conditions, revealed few, if any, channels extending into the granule interior. This discrepancy suggested that channels within wheat starch granules were filled at least in part with protein. Removal of protein with protease facilitated greater access of methanolic merbromin to channels and/or cavities for both granule types. For A-type starch granules, relatively large channels were observed in the equatorial groove region, while finer channels originated from other regions of the granule. This work reports the first visualization of B-type granule channels, which most frequently occurred as less-defined voids (as opposed to the fine, discrete channels of A-type granules) extending to granule surfaces. Channels of A- and B-type starch granules appeared to facilitate transfer of chemical reagent into the granule matrix, though this effect was aided by granule swelling (hydration) and/or removal of channel-associated protein.     

Biochemical Basis of Kernel Milling Characteristics and Endosperm Vitreousness of Maize

Chemical characteristics of 18 normal maize grain samples, having a wide range of physical properties (endosperm vitreousness, kernel friability and milling characteristics), were analysed and related to physical properties. Measurement of damaged starch showed that starch behaved as a passive filler in endosperm. Endosperm protein content and class, as determined from extractability properties and reversed-phase high-performance liquid chromatography, were correlated with kernel physical properties. Endosperm vitreousness and kernel mechanical properties (kernel friability and milling characteristics) were related to different components, however. Vitreousness seems to be linked to the proportion (%) of the two γ-zein fractions, whereas friability increased when α-zein content decreased and when salt extractable protein content increased.     

色氨酰-tRNA合成酶基因WRS1调控水稻种子发育

【目的】氨酰-tRNA合成酶（aminoacyl-tRNA synthetases, aaRSs）与遗传信息传递密切相关,已发现植物中aaRSs家族蛋白在维持翻译功能之余,还参与配子发生与胚发育、质体的早期发育以及免疫信号的感知与病害防御等生物学过程。本研究利用水稻胚乳发育缺陷突变体,分析水稻色氨酰-tRNA合成酶（WRS1）在胚乳发育中的作用,证明WRS1基因编码一个影响水稻胚乳发育的关键因子。【方法】本研究通过甲烷磺酸乙酯（ethyl methane sulfonate, EMS）诱变籼稻（Oryza sativa subsp. indica）品种N22,筛选到一个稳定遗传的水稻粉质胚乳突变体（wrs1）,图位克隆获得目标基因。对wrs1成熟种子进行形态学观察以及淀粉相关理化性质测定,利用细胞学切片分析wrs1发育中胚乳的结构,利用实时荧光定量PCR（quantitative real-time PCR, qRT-PCR）和GUS活性染色分析基因表达模式,通过qRT-PCR比较野生型与突变体花后12 d胚乳中淀粉合成相关基因表达情况,免疫印迹检测野生型与突变体成熟种子中淀粉合成酶蛋白积累情况,使用全自动氨基酸分析仪测定游离氨基酸含量。【结果】 wrs1突变体幼苗表现出明显的发育滞后且逐渐蔫萎死亡,从杂合突变体（WRS1wrs1）中分离到的粉质籽粒呈现明显的腹部皱缩,粒厚、千粒重下降,同时总淀粉含量下降,糊化淀粉的峰值黏度和崩解值均低于野生型。wrs1突变体发育胚乳中复合淀粉颗粒变小,排列疏松。WRS1定位于第12染色体长臂约183 kb的区间内,测序发现编码色氨酰-tRNA合成酶（tryptophanyl-tRNA synthetase, WRS）基因的第6外显子上发生单碱基替换,导致一个保守位置上的甲硫氨酸被替换。wrs1突变体中大部分淀粉合成相关基因表达量下调,且野生型与突变体间基因表达的变化与相应蛋白积累的差异存在不一致的趋势。wrs1突变体籽粒中蛋白质积累降低,而游离氨基酸含量显著升高。【结论】 WRS1编码色氨酰-tRNA合成酶,该基因突变后通过影响氨基酸稳态和蛋白质合成,造成淀粉合成相关基因异常表达从而影响淀粉的合成与积累,导致种子发育缺陷。     

Blue Maize: Morphology and Starch Synthase Characterization of Starch Granule

The use of pigmented maize varieties has increased due to their high anthocyanins content, but very few studies are reported about the starch properties of these grains. The aim of this work was to isolate the starch granules from pigmented blue maize and carry out the morphological, physicochemical, and biochemical characterization studies. The proximate composition of starch granules showed high protein contents, after purification, the blue maize starch presented lower protein amount than starch from white maize (control). Although the purity of starch granules was increased, the damaged starch (determined for the Maltase cross absence) was also increased. Scanning electron microscopy showed the presence of some pores and channels in the blue maize starch. The electrophoretic protein profiles showed differences in the bands that correspond to the enzymes involved in the starch biosynthesis; these differences could explain the variation in morphological characteristics of blue maize starches against starch from white maize.     

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.     

Location of Starch Granule-associated Proteins Revealed by Confocal Laser Scanning Microscopy

Distinct locations of starch granule-associated proteins were revealed using a protein-specific dye with confocal laser scanning microscopy (CLSM). The dye, 3-(4-carboxybenzoyl) quinoline-2-carboxaldehyde, fluoresces only after it reacts with primary amines in proteins, thereby removing background interference from residual dye. CLSM has the capability to discern fluorescence-labelled protein distribution in an optical slice of an intact starch granule while it is still in an intact state. With these techniques, starch granule proteins were revealed to be concentrated in internal concentric spheres in potato, maize, and wheat starches. Spheres were more distinct in potato starch than in other starches. Amylose-free potato and waxy maize starches showed no protein spheres, indicating that the internal protein spheres are composed of granule-bound starch synthase (GBSS). Identification of GBSS suggests the location of biosynthesis of amylose in starch granules, as well as spatial and temporal aspects of biosynthesis.     

小麦胚乳A、B型淀粉粒分离纯化方法研究

为了能够准确研究小麦籽粒胚乳中A、B型淀粉粒的形成机理、化学组分及理化特性,对前人分离提纯A、B型淀粉粒的方法进行改进,提出了适于小麦A、B型淀粉粒分离提纯的常量法和微量法。用4个不同淀粉含量类型的小麦品种籽粒对此方法进行验证,结果表明4个品种A、B型淀粉粒在常量法中的分离纯度分别达到79.46%~85.23%和90.27%~96.43%,在微量法中的分离纯度分别达到92.68%~96.70%和96.48%~99.00%。在常量法和微量法中,A型淀粉粒的分离纯度与品种淀粉含量成正相关, B型淀粉粒分离纯度与品种淀粉含量成负相关;而A、B型淀粉粒在两种方法中的分离产率与品种淀粉含量没有显著关系。     

西藏冬青稞胚乳淀粉粒发育特征研究

为了解青稞胚乳淀粉及淀粉粒形成与生长特征,以西藏育成青稞品种冬青8号为材料,对籽粒发育过程中胚乳灌浆速度、淀粉积累量及淀粉粒的产生、二维面积、粒径变化进行了分析。结果表明,胚乳发育过程中,干物质和淀粉积累量呈S型曲线,两者呈正相关。花后5d,青稞胚乳中可零星见到粒径和二维面积较小的A型小淀粉粒;花后10~15d,A型小淀粉粒数量显著增大,但粒径和二维面积增加较慢;花后20d,B型小淀粉粒可能已经形成,与A型小淀粉粒组成一个复合群体;花后25d,形成了粒径10μm的A型淀粉粒、粒径5~10μm的B型淀粉粒和粒径5μm的C型淀粉粒;花后30~55d,不同粒径的淀粉粒数量和二维面积逐渐增加,其中,C型淀粉粒数量不断增加直至籽粒成熟。青稞成熟籽粒胚乳中,淀粉粒的粒径为1.45~44.76μm,二维面积为3.56~1 750.8μm2;A型淀粉粒形状为近圆形,表面光滑,个别表面附着有C型淀粉粒,B型淀粉粒形状有近圆形、椭圆形多种类型,C型淀粉粒形状比B型淀粉粒的变异更大。     

Starch granule morphology in oat endosperm

Mature and developing oat (Avena sativa) grains were sectioned and image analysis methods used to estimate the starch granule-size distribution and morphology in endosperm cells. This showed that oat endosperm cells contain two types of starch granule: compound starch granules such as those seen in rice endosperm and in most other grasses; and simple granules similar to the B-type starch granules seen in the endosperm of Triticeae species such as wheat (Triticum aestivum). The simple granules in oats are similar in size and relative abundance to B-type granules in Triticeae suggesting that they may share a common evolutionary origin. However, there is a fundamental difference between oats and Triticeae in the timing of granule initiation during grain development. In Triticeae, the B-type granules initiate several days after the A-type granules whereas in oats, both the simple and compound granule types initiate at the same time, in early grain development.     

Relationship between the corneous and floury endosperm content and the popped sorghum quality

Popcorn is a healthy snack suggested by nutritionists. However, some countries in Europe, Asia, and South America have evaluated the use of sorghum as a popped cereal. Therefore, this study aims to evaluate the content of corneous and floury endosperm of sorghum and its influence in the popped sorghum quality. Five red varieties and three white varieties were evaluated. The physical and microstructural characteristics of the raw varieties were evaluated. The correlation matrix showed that physical properties such as the pericarp thickness, the hectoliter weight, and the type of endosperm are crucial to obtain popped sorghum. A high percentage of corneous endosperm and the size distribution of starch granules in the floury endosperm determine the popping ability of sorghum. The analysis of the principal components showed that the Paloma variety was the most suitable to obtain popped sorghum.