Relationships among the chalkiness,kernel size and endosperm cell morphology of rice kernels at different spikelet positions within a panicle

The occurrence of chalky kernels in rice is causally related to kernel size and endosperm morphology. This study aimed to investigate the occurrence of chalky kernels by analyzing kernel size, and the number and area of endosperm cells. Spikelets were sampled from upper and middle primary branches and lower secondary branches in a panicle, and divided into four categories: upper, middle, and lower perfect (PF) kernels and lower milky-white (MW) kernels. On the lower secondary branches, there was a higher percentage of chalky kernels, with smaller kernel lengths, widths and thicknesses, than the kernels on the upper and middle primary branches. MW kernels were smaller in size than PF kernels even on the same lower secondary branches. Regardless of grain appearance quality traits, the total areas of endosperm cross sections in lower kernels were significantly smaller than in upper kernels owing to the decreased cell area, and there was a significant negative correlation between the number of cells and average cell area. When the numbers and the areas of cells were analyzed using angular 30° intervals from the line connecting the center point and the dorsal vascular bundle, the MW kernels had significantly less cells than PF kernels near the ventral side at 120–180°. Thus, the decrease in the number of cells near the ventral side was a main causal factor in the decrease in MW kernel widths compared with PF kernel widths, and this suggested that cell division in MW kernels was inhibited at the early grain-filling stage.     

Microstructure of hard and soft kernels of barley

Kernel hardness, an important quality trait of cereal grains, is known to influence pearling properties and malting quality of barley. To understand the endosperm micro-structural features of kernels and their relationship to kernel hardness, endosperms of three hard and three soft hulled spring barley lines based on single kernel characterization system hardness index were observed under light (LM) and scanning electron (SEM) microscopy. Under LM, endosperm cell wall of the three hard kernel lines was significantly thicker than that of the three soft kernel lines. Hard and soft lines showed differences in the degree of starch-protein association and continuity of protein matrix under the SEM. Hard kernel lines with a continuous protein matrix exhibited greater starch-protein adhesion than the soft kernel lines, suggesting that starch-protein binding may be one of the factors influencing barley kernel hardness. SEM of flour particles of soft kernel lines showed numerous well defined individual A and B-type starch granules, while, flour of hard kernel lines mostly showed small flour aggregates with few individual starch granules.     

Barley for food: Characteristics,improvement, and renewed interest

Barley (Hordeum vulgare vulgare L.) is an ancient cereal grain, which upon domestication has evolved from largely a food grain to a feed and malting grain. However, barley food use today remains important in some cultures around the world, particularly in Asia and northern Africa, and there is renewed interest throughout the world in barley food because of its nutritional value. This review covers basic and general information on barley food use and barley grain processing for food use, as well as an in-depth look at several major aspects/traits of interest for barley food use including kernel hardness and colour, grain starch, and β-glucan contents. These traits are described in terms of their effects on processing and nutrition, as well as their inheritance and the prospects for barley improvement through breeding. Whereas, the aspects listed above have been studied relatively extensively in barley in terms of content, form, genetics, physiology, and in some cases nutritional quality, little is know about functional properties for processing and food product development. Renewed interest in barley for food uses largely centres around the effects of β-glucans on lowering blood cholesterol levels and glycemic index. Wholegrain barley foods also appear to be associated with increased satiety and weight loss. There is great potential to utilise barley in a large number of cereal-based food products as a substitute partially or wholly for currently used cereal grains such as wheat (Triticum aestivum), oat (Avena sativa), rice (Oryza sativa), and maize (Zea mays).     

Magnetic resonance imaging and analyses of tempering processes in rice kernels

This research involved a magnetic resonance imaging (MRI) technique that was applied to examine water distribution and migration in single rice kernels during the tempering process. The imaging experiments were performed in a Bruker 9.4T MRI system. Three-dimensional spin-echo (SE) imaging sequences were optimized by adjusting the scanning parameters of echo time (TE) and repetition time (TR) to obtain images with maximum contrast. The MR images showed that the moisture distribution in the rice kernel is non-uniform and compartmental. The embryo region exhibited much higher MR signal intensity than the starchy endosperm portion. The tempering process was analyzed with spatial-temporal signal intensities of the endosperm following the drying process of the rice kernel. The transient change of the signal intensities in the endosperm was well fitted with a double exponential function suggesting that both convection and diffusion contributed to the reduction of the moisture gradient within the rice kernel during tempering. This hypothesis was further supported by the experimental data of the insulated rice kernel whose convective mass transfer was excluded. The experimental results revealed that MR imaging of rice kernels could be used as an efficient tool to examine the mechanisms of moisture migration within cereal grains.     

Evaluation of malting barley quality using exploratory data analysis. II. The use of kernel hardness and image analysis as screening methods

This paper presents an exploratory investigation of the use of image analysis and hardness analysis of barley kernels for characterisation and prediction of malting quality. A sample set of fifty barley samples representing 15 spring barley and 10 winter barley varieties grown at two locations in Denmark was used. The samples were micro-malted and mashed and analysed for 13 quality parameters according to the official methods of the European Brewery Convention. A sub-sample of the barley samples was analysed on two different single kernel instruments: (1) Foss Tecator GrainCheck was applied for non-destructive recording of single kernel size and shape (width, length, roundness, area, volume and total light reflectance) and (2) Perten Single Kernel Characterization System 4100 was applied for single kernel hardness and weight determinations. The eight variables from these single seed analyses have been used in two different ways, either as means and standard deviations, or as appended histogram spectra representing 250 kernels from each bulk sample. By the two methods, it has been possible to obtain reasonable Partial Least Squares Regression (PLSR) models for the structural and physical part of the malting quality complex associated to malt modification, but it was as expected impossible to predict the biochemical parameters associated with nitrogen chemistry and enzymatic power. The best model was achieved for (1→3, 1→4)-β-D-glucan in barley. The hardness of the barley kernels is by far the most important variable for describing malting performance. The additional use of the morphological data as acquired by fast non-destructive image analysis, however, also reveals some malting quality information by improving the calibration models based on hardness alone. The brightness of the kernels is by far the most important GrainCheck variable but also kernel size and shape is associated to malting performance. In general, the utilisation of the single kernel readings (used as histogram spectra), compared to sample mean and standard deviation, did not provide additional information for an improved prediction of the malting quality parameters.     

Study of kernel structure of high-amylose and wild-type rice by X-ray microtomography and SEM

Rice kernels of a transgenic high-amylose rice line and its wild type were examined by a high-resolution X-ray microtomography (XMT) and an environmental scanning electron microscope. Two-dimensional (2-D) cross-sectional images and 3-D objects from XMT were reconstructed and analyzed to elucidate their structural features. The lack of two isoforms of starch branching enzyme, termed SBEI and SBEIIb in high-amylose rice (HAR), resulted in a distinctly different grain inner density than wild-type rice (WTR). HAR had smaller, elongated starch granules with air spaces inside the kernels resulting in an opaque grain, whereas WTR had a tight endosperm with little air space and polygonal starch granules. XMT allowed a full 3-D characterization of the rice kernel structure and revealed that air space distribution was not uniform in the HAR kernel.     

Processing conditions influencing the physical properties of French fried potatoes

Summary Achieving optimal colour and texture in French fries requires careful control of the unit operations that convert the raw potatoes into fries. The effects of variation in blanching, drying and finish frying conditions on puncture properties (peak force and peak deformation) and Hunterlab L (lightness) values of French fries were investigated. Fries blanched by low-temperature long-time (LTLT) conditions had larger peak force, peak deformation and L value than fries processed by standard conditions. High-temperature short-time (HTST) blanching increased lightness but decreased peak force and peak deformation. For drying, the colour and textural quality of French fries processed by standard conditions were better than those processed by the drying alternatives. For finish frying, LTLT conditions increased peak force whereas HTST conditions increased lightness. Therefore, a compromise has to be made in processing conditions to optimise both colour and textural quality. Even after finish frying, compositional differences within potato tubers influenced texture, both between and within French fries.     

Hardness Distribution and Endosperm Structure on Polishing Characteristics of Brewer’s Rice Kernels

Abstract

This study was designed to determine the effects of the hardness distribution and the endosperm structure on the polishing characteristics of brewer’s rice kernels. We used four brewer’s rice cultivars, Kairyo-omachi, Hattan-nishiki No. 1, Senbon-nishiki and Yamada-nishiki. The broken kernel ratios in Kairyo-omachi and Hattan-nishiki No. 1 were significantly higher than those in Senbon-nishiki and Yamada-nishiki. Vickers hardness (VH) values in white-core tissues in kernels differed among varieties, which were significantly lower in Kairyo-omachi and Hattan-nishiki No. 1. However, no varietal differences were observed in VH values in the peripheral translucent tissues surrounding the white-core tissues. The tissues along the dorsoventral axis were softer than those along the longitudinal axis of the kernels. The tissues on the ventral side were softer than those on the dorsal side. Scanning electron microscopy (SEM) observations revealed the presence of closely arranged compound starch granules and few varietal differences in the peripheral translucent tissues surrounding the white-core tissues. However, as compared with Yamada-nishiki and Senbon-nishiki, in Hattan-nishiki No. 1 and Kairyo-omachi, the starch granules were loosely packed and the airspaces between the starch granules were more numerous in the white-core tissues. A higher number of airspaces and less starch were present in the endosperm cells along the dorsoventral axis when compared with along the longitudinal axis and on the ventral side than on the dorsal side. The present study showed that polishing characteristics are closely related with the endosperm structure, which is characterized as the density of starch granules.     

Barley (1→3; 1→4)-β-glucan and arabinoxylan content are related to kernel hardness and water uptake

Harder kernels in barley are thought to be a factor affecting the modification of the endosperm during malting by restricting water and enzyme movement within the endosperm. The objective of this study was to investigate the relationship between kernel hardness, water uptake and the endosperm composition in barley. A range of barley samples from 2003 and 2004 crops were analyzed for kernel hardness by the Single Kernel Characterization System, water uptake during steeping and chemical composition of the endosperm including (1→3; 1→4)-β-glucan, arabinoxylan and total protein. Both (1→3; 1→4)-β-glucan and arabinoxylan content of the endosperm were correlated significantly with kernel hardness in barley samples from both 2003 (r=0.873 and 0.601, respectively, p<0.01) and 2004 seasons (r=0.764 and 0.501, respectively, p<0.01). Hardness of the kernel was highly correlated with its water uptake in both 2003 and 2004 samples (r=−0.853 and −0.752, respectively, p<0.01). β-Glucan content of the endosperm was also correlated significantly with the kernel water uptake for both years (2003: r=−0.752, p<0.01; 2004: r=−0.551, p<0.01). Arabinoxylan content of the endosperm was correlated significantly with the kernel water uptake for the 2003 barley but not for 2004 barley (2003: r=−0.523, p<0.01; 2004: r=−0.151, p>0.01). Protein content of the endosperm was not correlated with the kernel hardness in either year. These results demonstrate that endosperm cell wall components may have significant impact on kernel hardness as well as water uptake of barley.     

Endosperm Texture in Wheat

One of the fundamental means of classifying wheat is through its endosperm texture. It impacts significantly on the milling process affecting among other things flour particle size and milling yield. Hardness in wheat is largely controlled by genetic factors but it can be affected by the environment and factors such as moisture, lipid, and pentosan content. The principal genetic locus controlling endosperm texture in wheat, Ha, is located on the chromosome 5D. At this locus several genes, notably the puroindolines, have been identified. Puroindolines are the major components of the 15 kDa protein band associated with starch granules that is more abundant in soft wheats than in hard. Recently the puroindolines have been shown to enhance grain hardness in rice. In this review we discuss the structure of hard and soft wheat endosperm with particular emphasis on when differences in endosperm texture can be detected in the developing seed. The role of the environment and other factors that may affect the endosperm texture is also examined together with the role of the puroindoline genes at theHa locus. Finally, we compare endosperm hardness in wheat and in barley.     

Crop management affects dry-milling quality of flint maize kernels

Dry-milling performance of maize (Zea mays, L.) kernels primarily depends on their hardness. The flint type is harder than the dent and semi-dent maize, yielding a higher proportion of big endosperm pieces in the mill. Nevertheless, crop growing conditions could modify milling properties. The objective of this work was to analyze the effect of different crop environments and management practices on dry-milling quality of flint maize kernels. Two orange-flint hybrids from different eras of breeding differing in flint type expression and grain yield potential were evaluated. They were grown at three different locations of the Argentina's main maize-production area under different sowing dates, plant densities, and fertilization rates during two growing seasons. Crop post-silking growth, grain yield and its components (kernel number and weight), kernel size and hardness-associated properties (test weight, percent floaters and milling ratio), and flaking-grit yield were analyzed. Most of observed differences in physical properties of kernels, particularly for the high-yielding new hybrid with unstable flint expression, were associated with the source-sink ratio established during the post-silking period (explored range from 154 to 617 mg kernel⁻¹). This variable mainly results from changes in crop growth during that period. Increases in weight per kernel improved hardness-associated properties. High crop grain yields together with top dry-milling quality were achieved when the new high-yielding hybrid was cropped with an appropriated crop management.     

Evaluation and analysis the chalkiness of connected rice kernels based on image processing technology and support vector machine

In order to determine the location and type of rice chalkiness accurately, image processing techniques were adopted to process acquired rice kernel images. Connected rice kernels were separated from each other using a convex point matching method. Chalkiness was extracted according to the differences in grayscale levels between chalky and normal regions in the rice kernel and chalky rice kernels were classified by a support vector machine (SVM). The results showed that 2–5 connected rice kernels could be separated accurately using this method and chalky areas could be extracted. The classification accuracy for indica rice and japonica rice reached 98.5% and 97.6%, respectively, by using SVM. Hence, the measurement results are accurate and reliable, and the presented work provides a theoretical and practical basis for the further application of computer vision technology to chalkiness detection.     

The effects of puroindoline b on the ultrastructure of endosperm cells and physicochemical properties of transgenic rice plant

Endosperm texture is an important factor governing the end-product quality of cereals. The texture of wheat (Triticum aestivum L.) endosperm is controlled by puroindoline a and b genes which are both absent in rice (Oryza sativa L.). It has been reported that the endosperm texture of rice can be modified by puroindoline genes. The mechanism, however, by which puroindolines affect the ultrastructure of rice endosperm cells remains to be investigated. In this study, we observed the ultrastructure of endosperm cells and the morphology of isolated starch granules of the transgenic rice expressing the puroindoline b gene. SEM and TEM observations indicated that compound starch granules were embedded within the matrix material in non-transgenic rice, Nipponbare, whereas they were surrounded by spaces in the transgenic rice. The morphology and size of each starch granule were not different between non-transgenic and the transgenic rice. However, the transgenic rice flour showed smaller particle size, higher starch damage, and lower viscosity during gelatinization than that of non-transgenic rice. These results confirm that puroindoline b reduces the grain hardness in rice. Moreover, the results also suggest that puroindoline b functions at the surface of compound starch granules, and not on polygonal starch granules in rice endosperm.     

Structure,chemical composition and enzymatic activities of pearlings and bran obtained from pearled wheat (Triticum aestivum L.) by roller milling

While abrasive pearling (also referred to as debranning) of wheat kernels prior to milling increases the quality of the resultant flour for producing bread, the potential applications of the co-products of pearling is largely unknown. We studied the impact of different degrees of pearling (0, 3, 6, 9 and 12% by weight) on the composition of pearlings and bran obtained when subsequently roller milling pearled wheat kernels. Pearling does not remove the kernel outer tissues homogeneously as abrasion affects especially the accessible parts of the kernels. Nevertheless, the first 3% removed consisted of mainly pericarp. With 6% or more removed, a significant amount of starchy endosperm ended up in the pearlings. The starting bran material and bran obtained by subsequent roller milling of pearled wheat kernels had similar compositions but the latter had a lower average particle size. Moreover, removal of the outermost kernel layers substantially decreased the enzyme activity levels in the bran.     

The potential of naked barley sourdough to improve the quality and dietary fibre content of barley enriched wheat bread

The possibility of using naked barley for food products is gaining popularity due to its dietary fibre content, especially β-glucans. The technological process (dough preparation, fermentation and baking) influences bread quality but also may contribute to degradation or preservation of valuable grain components. The aim of the study was to investigate the effects of different wholemeal barley flour share and bread production method on the quality of bread and non-starch polysaccharides content and solubility.Barley enriched bread contained more both soluble and insoluble dietary fibre and β-glucans, products of 40% barley share contained 67% more total dietary fibre and 160% more β-glucans than control. However, barley incorporation decreased the amount of soluble arabinoxylans. High barley contents contributed to the breads’ volume reduction by 14% and change in their crumb and crust colour. However, barley enriched breads gained higher ratings of taste than wheat bread. Barley sourdough fermentation improved breads’ volume, colour and sensory properties. Sourdough fermentation also resulted in higher concentration of dietary fibre, arabinoxylans and β-glucans. The beneficial effect of barley addition to wheat bread may be successfully enhanced by using barley wholemeal sourdough fermentation.     

Quantification and distribution of kafirins in the kernels of sorghum cultivars varying in endosperm hardness

Kafirins extracted from the endosperm of seven sorghum [Sorghum bicolor (L.) Moench] cultivars were analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and enzyme-linked immunosorbent assay (ELISA). Kafirins extracted from the vitreous and floury endosperm portions within the kernel were also analysed by these techniques. The ELISA results indicated that the level of all the three kafirins was high in the hard endosperm kernels. The level of γ-kafirin was particularly higher in the vitreous endosperm portions of these kernels. The ratio of γ-kafirin to the α-kafirin was, however, higher for the floury portions of soft kernels. Tissue print immunoblotting revealed that the β- and γ-kafirins were concentrated in the central floury endosperm portions of soft kernels, whilst α-kafirin was distributed more uniformly throughout the endosperm. In contrast, all three kafirins were distributed uniformly throughout the endosperms of hard kernels. The data indicate that the content, as well as the distribution, of kafirins within the kernel is different in grains varying in endosperm hardness.     

胚乳外观标记与RVA谱理化指标相结合辅助改良早籼稻食用品质

对具有较低和中等表观直链淀粉含量的浙辐504和IR64的杂交后代进行观察,发现胚乳外观存在4种类型：乳白色、云雾状、透明状及各外观混合体。与胚乳外观紧密关联,表观直链淀粉含量(AAC)也相应有4种含量水平：明显低AAC变异型、浙辐504型、IR64型和介于双亲的中间型。RVA谱分析表明,不同胚乳外观的淀粉粘滞特性差异明显。透明状外观尽管AAC相仿,但个体间淀粉粘滞性分化明显,只有个别优良品系的RVA谱与优质亲本IR64相似。表明以胚乳外观标记和RVA谱理化指标辅助选择可有效控制表观直链淀粉含量和淀粉粘滞性,是改良早籼稻米品质的一条有效途径。     

Difference in the Physical Properties of White-Core and Non-White-Core Kernels of the Rice Varieties for Sake Brewing is Unrelated to Starch Properties

Abstract

This study was designed to determine whether or not the difference in the physical properties between white-core and non-white-core kernels of the rice varieties for sake brewing is associated with their starch properties. We used two rice cultivars for sake brewing, Senbon-nishiki and Yamada-nishiki, from three different plots in Hiroshima prefecture. Hardness values of kernels were significantly higher in non-white-core than in white-core kernels in both varieties. Vickers hardness (VH) values were lowest at the center of the kernel in both types of kernels. VH values of white-core tissues of white-core kernels were significantly lower than those of corresponding tissues of non-white-core kernels. No significant differences were observed between the two types of kernels in VH values of the surrounding translucent tissues and in the starch properties (amylose content, pasting properties analyzed using a rapid viscoanalyzer and gelatinization properties analyzed using a differential scanning calorimetry). These results suggest that the difference in physical properties between the two types of kernels of the rice varieties for sake brewing are associated with the difference in structure of endosperm cells and not in starch properties.     

Field emission scanning electron and atomic force microscopy,and Raman and X-ray photoelectron spectroscopy characterization of near-isogenic soft and hard wheat kernels and corresponding flours

Secondary field emission scanning electron microscopy (FE SEM), atomic force microscopy (AFM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to investigate native near-isogenic soft and hard wheat kernels and their roller milled flours. FE SEM images of flat-polished interior endosperm indicated distinct differences between soft and hard wheats with less internal continuity in the soft wheat, whereas individual starch granules were much less evident in the hard kernel due to a more continuous matrix. AFM images revealed two different microstructures. The interior of the hard kernel had a granular texture with distinct individual spheroid features of 10–50 nm while the images obtained for the soft kernel revealed less distinct small grains and more larger features, possibly micro-structural features of starch granules. Raman spectra resolved identical distinct frequencies for both kernel types with slightly different intensities between types. Finally, the chemical surface compositions of flour for these two types of kernels obtained by XPS provided subtle insight into the differences between soft and hard wheat kernels. These combined advanced microscopic and spectroscopic analyses provide additional insight into the differences between the soft and hard wheat kernels.     

Characterisation of Starch from Inner and Peripheral Parts of Normal and Waxy Barley Kernels

A previous microscopical examination of barley kernels indicated an uneven distribution of amylose in the waxy cultivar SW7142-92, where the subaleurone layer was strongly stained by iodine. To explain these results, starch was isolated from fractions of inner and peripheral parts of kernels of the waxy cultivar and a cultivar with normal starch. Analyses of amylose content showed a higher concentration of amylose in starch from the outer part of the waxy barley kernel, where the amylose, determined by a colorimetric method, made up 8·6% of the starch compared with 5·9% in the middle and 2·2% in the innermost part of the waxy kernel. This difference in amylose distribution was not observed in the normal starch kernel. The results were confirmed by gel permeation chromatography. No differences in amylopectin chain length distribution were detected by size exclusion HPLC and HPAEC-PAD of amylopectins from different parts of the barley kernels.