Moisture Distribution in a Mature Soft Wheat Grain by Three-Dimensional Magnetic Resonance Imaging

Moisture-tempering is typically performed prior to first break in wheat milling operations to enhance separation of bran, germ, and endosperm. To improve the milling performance and to increase yield, a better knowledge of moisture distribution and migration in individual wheat grains during tempering is essential. The research described herein was conducted to demonstrate the non-destructive measurement of the three-dimensional (3D) distribution of moisture in a single wheat grain. A 3D magnetic resonance imaging (MRI) technique was adapted for the probing of single wheat grains at storage moistures (c.12% wet basis). The technique is demonstrated in this report on one grain. A 3D projection reconstruction (3DPR) technique was used to acquire high resolution proton density images. The spatial resolution of the images was 94×94×94 μm³. The 3D proton density images were related to the 3D moisture distribution in the wheat grain. At 12% moisture content, the moisture distribution in the starchy endosperm of the wheat was not uniform. The variation of the moisture distribution was from 7·3% to 16·4% wb.     

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.     

Moisture distribution in rice grains used for sake brewing analyzed by magnetic resonance imaging

Water absorption in individual white-core and non-white-core grains of rice varieties used in sake brewing was observed during soaking by magnetic resonance imaging (MRI). Water was absorbed faster in white-core grains than in non-white-core grains and was pooled in the core. Moisture distributions were compared using the line profiles of nuclear magnetic resonance signal intensities (SI profiles) generated from magnetic resonance images of grains soaked for 2 h. SI profiles of white-core and non-white-core grains overlapped despite slight differences in the central and intermediate regions of the grains. A white-core-like structure with loosely packed starch granules was found to exist in the endosperm of non-white-core grains. SI profiles of grains polished to 70% of the yield weight of brown rice were similar in shape to those of grains polished to 90% of the yield, but their overall moisture content was higher after the removal of the hydrophobic grain periphery. A varietal difference in the thickness of the intermediate region, which may affect fissuring resistance in the polishing process, was detected in SI profiles. Differences in water absorbability between parents and their offspring were also apparent from their SI profiles. MRI enabled the detection of variety-specific water-absorption properties in grains.     

Moisture distribution of soaked rice grains observed by magnetic resonance imaging and physicochemical properties of cooked rice grains

Moisture distribution in individual polished rice grains was observed during soaking by magnetic resonance (MR) imaging, and a nuclear magnetic resonance (NMR) signal intensity profile (SI-profile) was generated from the MR image. The water penetration pattern during soaking roughly showed dissimilar trends between different varieties of japonica and japonica-indica hybrid rice. NMR signal intensity at the completion of water absorption varied within each grain; high at the periphery and the central region and low in the area between the periphery and the central region. High moisture content within the central region is due to loosely packed starch granules. The SI-profile was congruent for grains of the same variety harvested in different regions and years and characterized a grain moisture distribution for each variety. Moisture distribution was compared using SI-profiles for varieties with different amylose contents and new varieties bred for specific end-uses in Japan. The NMR signal intensity, which is related to the moisture content, at the surface of soaked grain was negatively correlated to the grain amylose content. The NMR signal intensities at the surface of soaked grain negatively correlated with the overall hardness of the cooked rice grain as measured by the single-grain low-high compression test.     

含水量变化对米粒裂纹形成的影响与调控

稻米水分含量变化是引起籽粒裂纹发生和影响整米率的主要因素。潮湿米粒的快速干燥，干燥籽粒的浸水或回潮均会带来严重的裂纹。干燥后润谷可减少裂纹的发生。生产、加工、贮藏过程中可通过合理处理稻米水分含量减少裂纹发生，提高碾米品质。     

含水量变化对米粒裂纹形成的影响与调控

稻米水分含量变化是引起籽粒裂纹发生、影响整米率的主要因素。潮湿米粒的快速干燥,干燥籽粒的浸水或回潮均会带来严重的裂纹。干燥后润谷可以减少裂纹的发生。生产、加工、贮藏过程中可通过合理处理稻米水分含量减少裂纹发生,提高碾米品质。     

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.     

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.     

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.     

Visualisation of Moisture Distribution during Development of Rice Caryopses (Oryza sativa L.) by Nuclear Magnetic Resonance Microimaging

The moisture distribution in developing rice caryopses was visualised with nuclear magnetic resonance (MR) microimaging. Rice plants (Oryza sativa L. cv. Koshihikari) were grown outdoors in pots, and spikelets were sampled at various times after anthesis. Clear images could be obtained from young tissues, especially of the embryo, the pericarp vascular bundle, and the endosperm, up to 25 days after anthesis. Outlines of these structures, as revealed by their moisture distribution pattern, were largely consistent with various earlier morphological observations. Water observed in a relatively narrow zone in the center of the caryopsis 25 days after anthesis was considered to indicate a route for water supply or drain for the embryo. The fact that this band of water touched the corner of the embryo strengthened the above assumption. A striped pattern of water was observed on the surface of the endosperm in the three-dimensional images reconstructed from maximum intensity projections of the spikelets. This finding supports a previously stated hypothesis that water flows from the pericarp vascular bundle onto the nucellus.     

Pearling Quality of Canadian Barley Varieties and their Potential Use as Rice Extenders*

Barley can be used as an extender of rice to increase the nutritive value of the end-product. Specific quality barley is required if the processed barley is to resemble cooked white rice in colour and shape. The barley must pearl and split without the production of broken kernels or fines and yet produce desired end use quality. Barley endosperm texture and colour are key to determining these processing characteristics. Testing of Canadian barley types indicated the waxy type was most appropriate for pearling and processing as rice extender. It had a firm endosperm texture that was not steely and yet processed into a white product with few broken grains. Covered barley was of better quality than hull-less, as the former generally had fewer steely kernels as well as firmer endosperm texture. Differences observed between two- and six-rowed type were related to grain size and could be overcome by proper adjustments to processing conditions. Growing conditions affected kernel size and barley protein contents but to a lesser extent than barley type. L* brightness values, Particle Size Index and kernel size were found to be important predictors of barley quality for pearling and as rice extender.     

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.     

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.     

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.     

不同玉米品种子粒硬度差异及与含水率的关系

在北京和河南新乡两个生态区,通过设置不同品种和播期试验,利用手持便携式推拉力计测定玉米子粒不同含水率条件下胚、胚乳和顶部的硬度,明确玉米子粒脱水过程中硬度的变化规律,分析玉米子粒含水率与硬度之间的关系。结果表明,手持便携式推拉力计可以测定不同玉米品种及含水条件下子粒顶部、胚和胚乳的穿刺强度,用来表征子粒的硬度。子粒胚乳的硬度最高,其次是顶部,胚的硬度最低。子粒硬度随着含水率的降低逐渐升高,胚的硬度对含水率的变化最为敏感,顶部硬度对含水率的变化最不敏感。不同品种之间,子粒胚乳硬度对含水率的响应不同。生产中可通过测定胚乳硬度进行适宜粒收品种的筛选和适宜收获期的确定。     

不同玉米品种子粒硬度差异及与含水率的关系

在北京和河南新乡两个生态区,设置不同品种和播期试验,利用手持便携式推拉力计测定玉米子粒不同含水率条件下胚、胚乳和顶部的硬度,明确玉米子粒脱水过程中硬度的变化规律,分析玉米子粒含水率与硬度之间的关系。结果表明,手持便携式推拉力计可以测定不同玉米品种及含水条件下子粒顶部、胚和胚乳的穿刺强度,用来表征子粒的硬度。子粒胚乳的硬度最高,子粒顶部硬度次之,胚的硬度最低。子粒硬度随着含水率的降低逐渐升高,胚的硬度对含水率的变化最为敏感,顶部硬度对含水率的变化最不敏感。不同品种之间,子粒胚乳硬度对含水率的响应不同。生产中可通过测定胚乳硬度进行适宜粒收品种的筛选和适宜收获期的确定。     

Reliability of InGaAs focal plane array imaging of wheat germination at early stages

To assist our Kansas breeding program, we have developed nondestructive methods to test new lines of wheat for resistance to premature germination. The high sensitivity of subsurface imaging, compared with visual detection, α-amylase determination, or viscosity testing, permits germination detection at early stages. This report is concerned with detection reliability via chemical imaging of intact wheat kernels at early stages of germination by using an InGaAs focal plane detector array in the 1100–1700 nm range. Ninety kernels from each of six different cultivars, including HRW and HWW wheat, were exposed to moist conditions for 6, 12, 24, 36, and 48 h. Images of each 90 kernel group were examined, and images of those kernels exposed to moisture for 36 h were compared with images of kernels treated for 3 h as a control. Images of each were classified as sprouted or unsprouted. Criteria for classification included images of log 1/R at select wavelengths or images of select factors resulting from principle component analysis (PCA) treatment of reflectance intensity data from each pixel. Sprouted kernels determined by PCA factors 1 and 4 from 90 kernels tested in a 36-h moisture exposure numbered 87, 85, 80, 74, 70, 48 for six cultivars tested. Cultivar KS-2174 was shown to be distinctly more resistant to germination than the other cultivars. When KS-2174 was compared with Betty wheat, for all exposure times, Betty had approximately 45% more germinated kernels.     

Identification of the histological origin of durum wheat milling products by multispectral imaging and chemometrics

In the durum wheat industry, the milling process leads to the production of different fractions such as semolina, flours, bran and thirds. The histological origin and composition of these fractions are not easy to determine. Moreover, the proportions of kernel tissue in a given fraction depend on the wheat cultivar. In the present work, 4 batches of durum wheat were processed in an experimental semolina pilot plant leading to the extraction of 18 representative fractions. Multispectral images of both the final fractions and wheat kernels have been acquired with an in-house imaging system. By performing principal component analysis and a Kmeans procedure on the multispectral images of each fraction, a reference spectral fingerprint was assessed for every fraction. For each pixel of the images of kernel cross-section, it was possible to calculate its probability of belonging to a typical group of fingerprint, and then to build up a probability image. These probability images, presented in false colors, emphasized the areas in the kernels from which a given milled fraction was extracted. The images obtained in this way enable a more precise identification of the histological origin of the different milled fractions.     

Measurement and fissuring of rice kernels during quasi-moisture sorption by image analysis

Fissuring associated with kernel elongation was evident in a moisture-adsorbing environment at 15 °C of relative humidity 88.72±0.28% with moisture content from 6% (d.b.) to 16.3% (d.b.). The average length and width of 800 kernels was measured during the sorption test using a Cervitec Grain Inspector equipped with two digital cameras. Samples were exposed to both a moisture-adsorbing and desorbing environments at 15 °C with relative humidities of 23.4±0.53%, 55.9±0.27%, 70.98±0.28% and 88.72±0.28%. On image analysis, the kernels changed in size from 5.13 to 4.84 mm in length and 2.9 to 2.73 mm in width. Both length and width changed as expected during moisture-adsorbing and moisture-desorbing tests. Fissured kernel percent was related to changes in the average length of the kernels during the moisture-adsorbing tests. The average length and fissured kernel percent of rice kernels measured by image analysis may be considered as a reliable indicator of changes in their dimensions during quasi-static moisture sorption processes.     

Development of wheat kernels with contrasting endosperm texture characteristics as determined by magnetic resonance imaging and time domain-nuclear magnetic resonance

Spikes and seeds from diploid ‘einkorn’ wheat Triticum monococcum and two near-isogenic hard and soft common wheat (Triticum aestivum) lines were harvested at regular intervals from 7 days post-anthesis (dpa) and analysed by non-destructive magnetic resonance imaging (MRI) and time domain-nuclear magnetic resonance (TD-NMR). A large amount of free water occurred in rachises, glumes and awns of spikes collected at 7 dpa, and accumulated in the physiologically active cells of the endosperm at 21 dpa. In the final stages of kernel development, awns and seed embryos exhibited a high MR signal due to the presence of free water likely associated with biological activities. TD-NMR relaxation time distributions obtained by discrete exponential fitting, distributed exponential fitting and SLICING multivariate analysis offered detailed information on mobility behaviour of water molecules in developing seeds and were able to differentiate two soft and hard isolines from common wheat cv. Enesco at early stages of seed development.