Compressive Strength of Wheat Endosperm: Analysis of Endosperm Bricks

The material properties of wheat grain endosperm are central to its processing and end‐use quality. The preparation of geometrically‐defined endosperm specimens free of bran, germ, and pigment strand can facilitate the objective study of endosperm material properties. This study was conducted to characterize the material properties of wheat endosperm from two soft, two hard, and one durum wheat varietal samples. Additionally, each varietal sample was sorted according to vitreous or mealy kernel type. Endosperm ‘bricks’ approximately 0.76 × 2.08 × 1.06 mm were prepared using an abrading (Kernel Sanders, KS) device. Bricks were tested in compression using a texture analyzer (TA.XTPlus). Stress‐strain curves were used to calculate failure strain, failure stress, failure energy, and Young's modulus. Additionally, the effect of brick aging up to one month, and changes in moisture content (freeze drying, oven drying, and equilibration to ≈10.5–11% mc) were studied. Intrakernel variation was assessed by preparing two sibling bricks (one from each cheek) from individual kernels. Failure strain, stress, and energy all had relatively high model R² values (0.68, 0.79, and 0.75, respectively). The ANOVA model R² for Young's modulus was 0.46. All models indicated variety as a highly significant source of variation in brick material properties. The effect of vitreous versus mealy kernel type was not consistent across varietal samples. Brick age and moisture content did not significantly affect brick material properties. Analysis of sibling bricks indicated that the magnitude of intrakernel variation was similar to that observed for individual varietal lots of uniform vitreous or mealy kernel type. Overall, failure strain provided a ranking and mean separation most consistent with kernel texture market class. The results obtained in the present study, although similar to other published reports do not closely agree with them on the material properties of wheat endosperm. Similarly, published results of material properties often differ considerably. The source of these discrepancies are at present unknown, but in some circumstances they may relate to specimen orientation relative to the source kernel, as there was evidence for anisotropic behavior. A companion study compares the variation in kernel texture obtained with the single kernel characterization system (SKCS) with that obtained here using bricks.     

Collaborative Analysis of Wheat Endosperm Compressive Material Properties

The objective measurement of cereal endosperm texture, for wheat (Triticum spp. L.) in particular, is relevant to the milling, processing, and utilization of grain. The objective of this study was to evaluate the interlaboratory results of compression failure testing of wheat endosperm specimens of defined geometry. Parallelepipeds (bricks) and cylinders were prepared from individual soft and hard near‐isogenic wheat kernels and compressed in two orientations (parallel and perpendicular to the long brush‐to‐germ axis). Compression curves were used to derive failure stress, failure strain, work density (area under the curve), and Young's modulus. In all five laboratories, the ability to delineate hard from soft wheat endosperm material properties was quite high. Four laboratories compressed endosperm bricks in the same orientation, on edge; texture class (soft vs. hard) was consistently the greatest source of variation in analysis of variance models (F‐values from 417 to 1401, Young's modulus and failure stress, respectively). Failure stress was found to be the best overall means of measuring the difference in what is known in the vernacular as wheat hardness. Across laboratories, the absolute measures of all four material properties ranged on the order of about two‐ to threefold from low to high, although within a laboratory, results were highly consistent. Laboratory by texture class interaction was deemed to be of minor importance. Brick size and moisture content within the ranges tested were not major sources of variation, and cylinders prepared from endosperm produced results similar to those obtained from bricks. The results suggested that wheat endosperm might express some level of anisotropic behavior, as specimens compressed in the kernel orientation parallel to the long axis failed at lower strain and stress values, with lower work density, when compared with kernel orientation perpendicular to the long axis. A key feature of interlaboratory variation was identified as being instrument rigidity, a subject of ongoing research. In conclusion, the preparation of endosperm specimens of defined size and shape, in combination with compression failure testing at low moisture content (<18%), is useful for objectively delineating the phenomenon known as hardness. The study presented here will advance our ability to objectively measure cereal grain texture and the material properties of endosperm.     

Compressive Strength of Wheat Endosperm: Comparison of Endosperm Bricks to the Single Kernel Characterization System

The three major classes of endosperm texture (grain hardness) of soft and hard common, and durum wheat represent and define one of the leading determinants of the milling and end‐use quality of wheat. Although these three genetic classes are directly related to the Hardness locus and puroindoline gene function, much less is known about the kernel‐to‐kernel variation within pure varietal grain lots. Measurement of this variation is of considerable interest. The objective of this research was to compare kernel texture as determined by compression failure testing using endosperm bricks with results of whole‐kernel hardness obtained with the Single Kernel Characterization System 4100 hardness index (SKCS HI). In general terms, the variation obtained with the SKCS HI was of similar magnitude to that obtained using failure strain and failure energy of endosperm brick compression. Objective comparisons included frequency distribution plots, normalized frequency distribution plots, ANOVA model R², and coefficients of variation. Results indicated that compression testing and SKCS HI similarly captured the main features of texture classes but also reflected notable differences in texture properties among and within soft, hard, and durum classes. Neither brick compression testing nor the SKCS HI may be reasonably expected to correctly classify all individual kernels as to genetic texture class. However, modest improvements in correct classification rate or, more importantly, better classification related to end‐use quality may still be achievable.     

Influence of Bioprocessed Wheat Bran on the Physical and Chemical Properties of Dough and on Wheat Bread Texture

The aim of this work was to assess the influence of wheat bran addition on the rheological properties of dough and on subsequent wheat bread volume and texture. Two types of bioprocessed bran (fermentation with yeast or with yeast plus enzymes) were studied in breadmaking at a substitution level of 20% (sufficient to deliver 6 g of dietary fiber per 100 g of product, the minimum for the European Food Safety Authority high‐fiber nutrition claim). Fermentation activated endogenous enzymes of bran, which together with exogenous enzymes modified the state of fiber in bran, resulting in solubilization of arabinoxylans and slight degradation of the insoluble fiber. Fermentation and enzyme treatment of bran compensated for the increased hardness (+100%) and the volume‐decreasing (–21%) effect observed with untreated bran. Analysis with partial least squares regression suggested the efficacy of bioprocessing to be based on solubilization of arabinoxylans, smaller particle size of bran, lower pasting viscosity of starch, improved resistance to extension, and accelerated CO₂ production.     

Influence of High Molecular Weight Glutenins on Viscoelastic Properties of Intact Wheat Kernel and Relation to Functional Properties of Wheat Dough

High and low molecular weight glutenin subunits (HMW‐GS and LMW‐GS, respectively) are the main factors determining the viscoelastic properties of wheat dough. The mechanical and viscoelastic properties of 29 samples of wheat kernels differing in HMW‐GS were evaluated with load‐compression tests. Samples were grouped by genotypes differing in HMW‐GS composition (allelic variants: Glu‐A1: null, 1, 2*; Glu‐B1: 7, 7+8, 7+9, 13+16, and 17+18; Glu‐D1: 5+10, 2+12). Groups representing Glu‐A1 1 and 2*; Glu‐B1 7, 7+9 and 17+18; and Glu‐D1 5+10 generally possessed hard grain and showed the largest kernel elasticity values, while those representing subunits Glu‐A1 null; Glu‐B1 7+8; and Glu‐D1 2+12 had soft kernels and showed lower elastic work values. Genotypes possessing HMW‐GS 1, 17+18 and 5+10 gave large SDS‐sedimentation values and better dough viscoelastic properties than those with allelels: null, 7+8, and 2+12. Kernel hardness showed significant correlation with the dough‐strength‐related parameters: SDS‐sedimentation; dough mixing time; and the alveographic parameters, W and P. There was a negative correlation between kernel plastic work and dough mixing time and the dough tenacity/extensibility parameters, P/L. The significant relationship between sedimentation tests and kernel elastic work seems to indicate that elastic work is related to genotype (protein composition). The general tendency was that higher values in kernel elastic work and size corresponded to better dough rheological quality. Mechanical properties of the kernel were significantly related to the elastic behavior measured in a single wheat kernel. The use of the compression test on individual kernels is easy, rapid and nondestructive and therefore seems to show potential use as a rapid tool in breeding to improve wheat quality.     

Mechanical and Physicochemical Characterization of Vitreous and Mealy Durum Wheat Endosperm

The mechanical, physical, and biochemical characteristics of mealy and vitreous endosperm were investigated. Endosperm were obtained from four durum wheat cultivars grown under different nitrogen fertilization designs. The textural properties and the density of the endosperm were measured on hand‐shaped parallelepiped endosperm samples. Endosperm protein content and composition and also gliadin composition were investigated by HPLC. Mechanical tests showed that mealy and vitreous endosperm differed in hardness and vitreousness. Vitreousness increased with nitrogen fertilization supply whereas there was no variation among the different cultivars. Hardness seemed to be linked to genotype and insensitive to nitrogen supply. From this result, we concluded that hardness and vitreousness are not related. Endosperm protein content and gliadin‐to‐glutenin ratio were related to nitrogen supply and increased especially when nitrogen supply was applied at flowering. At the same time, endosperm vitreousness increased. Further biochemical analyses were performed on 270 kernels, mealy or vitreous, hand‐picked from 148 different crops. Results showed that protein content of vitreous endosperm exceeded 9.7% in >90% of the cases. The glia/glu ratio was a less accurate predictor of kernel vitreousness, indicating that, by itself, it cannot account for the change in kernel vitreousness. Endosperm vitreous texture would rise above a threshold content of 9.7% protein within the endosperm.     

Influence of Low Molecular Weight Glutenins on Viscoelastic Properties of Intact Wheat Kernels and Their Relation to Functional Properties of Wheat Dough

The mechanical and viscoelastic properties of intact wheat kernels of 36 wheat cultivars differing in low molecular weight glutenin subunit (LMW‐GS) composition (loci Glu‐A3, Glu‐B3, and Glu‐D3) were evaluated using load‐compression tests. Comparison among genotypic groups representing Glu‐3 allelic variants showed that groups representing the alleles Glu‐A3 b, c, and d; Glu‐B3 d, g, and h; and Glu‐D3 a, b, and d, had harder kernel texture, higher kernel elastic work and larger gluten strength‐related parameters than those possessing alleles Glu‐A3 e; Glu‐B3 f, i and j (translocation 1B/1R); and Glu‐D3 d. Modulus of elasticity (stress to strain ratio) showed low values (111.9–168.8 MPa) for allelic groups possessing poor elastic properties (Glu‐A3 e; Glu‐B3 f, i, and j; and Glu‐D3 d), and high values (179.8–222.6 MPa) for allelic groups possessing high kernel elastic properties (Glu‐A3 b c, and d; Glu‐B3 d, g, and h; and Glu‐D3 a, b and c). The highest values for gluten strength‐related parameters (SDS‐sedimentation, dough mixing time, and dough strength [W]) corresponded to allelic groups Glu‐A3 d; Glu‐B3 d and g; and Glu‐D3 d, while the lowest corresponded to Glu‐A3 e and Glu‐B3 j. No significant differences were observed among groups with regard to gluten extensibility parameters; however, the highest P/L value (least extensibility) corresponded to Glu‐B3 j, which indicates presence of 1B/1R translocation. Except for the Glu‐B3 j (translocation 1B/1R) allele, which presented more variation within samples, a general relationship between kernel viscoelastic properties and dough viscoelastic properties was observed; samples showing higher elastic work to plastic work ratio (E/P) tended to possess better gluten strength than cultivars with low E/P ratio.     

Molecular Structure and Organization of Starch Granules from Developing Wheat Endosperm

Wheat starches isolated from seeds harvested between 7 and 49 days after anthesis (DAA) were fractionated into large (>8 μm) and small (<8 μm) granules and studied for starch structure and architecture. Starch granules at 7 DAA possessed unimodal size distribution, whereas it was bimodal at later maturity stages. The apparent amylose fraction of starch granules at early maturity (7 and 14 DAA) consisted of intermediate‐type materials, whereas starch at later maturity stages (28 and 49 DAA) contained branched amylose. Wide‐angle X‐ray scattering (WAXS) revealed a well‐developed polymorphic structure already at 7 DAA. Although the presence of a small proportion of B‐type crystallites mixed with A‐type crystallites was observed in the X‐ray diffractogram of starches at early maturation (7 and 14 DAA), it was masked by the A‐type crystallites at later maturity stages. However, the large granules had a higher proportion of B‐type crystallites and lower relative crystallinity (RC) than their small‐granule counterpart. The iodine absorption properties of the starch granules demonstrated different levels of mobility of the starch polymers at different stages of maturity and the mobility of more glucan polymers in the large granule population compared with the small granules at the same maturity stage. Iodine did not change the characteristic A‐type crystalline pattern of starch, but it increased RC. Changes in peak width at half height based on WAXS data further suggested the possible interaction of iodine with amylopectin intercluster chain segments and branch chains in formation of inclusion complexes.     

Separation and Characterization of A- and B-Type Starch Granules in Wheat Endosperm

Mature wheat (Triticum aestivum L.) endosperm contains two types of starch granules: large A-type and small B-type. Two methods, microsieving or centrifugal sedimentation through aqueous solutions of sucrose, maltose, or Percoll were used to separate A- and B-type starch granules. Microsieving could not completely separate the two types of starch granules, while centrifuging through maltose and sucrose solutions gave a homogenous population for B-type starch granules only. Centrifuging through two Percoll solutions (70 and 100%, v/v) produced purified populations of both the A- and B-type starch granules. Analysis of starch granule size distribution in the purified A- and B-type granule populations and in the whole-starch granule population obtained directly from wheat endosperm confirmed that the purified A- and B-type starch granule populations represented their counterparts in mature wheat endosperm. Centrifugations through two Percoll solutions were used to purify A- and B-type starch granule populations from six wheat cultivars. The amylose concentrations and gelatinization properties of these populations were analyzed. All of the A-type starch granules contained higher amylose concentrations and had higher gelatinization enthalpies than did B-type starch granules. Although A- and B-type starch granules started to gelatinize at a similar temperature, B-type starch granules had higher gelatinization peak and completion temperatures than did A-type starch granules     

Influence of Amylose Content on Properties of Wheat Starch and Breadmaking Quality of Starch and Gluten Blends

The effects of amylose content on thermal properties of starches, dough rheology, and bread staling were investigated using starch of waxy and regular wheat genotypes. As the amylose content of starch blends decreased from 24 to 0%, the gelatinization enthalpy increased from 10.5 to 15.3 J/g and retrogradation enthalpy after 96 hr of storage at 4°C decreased from 2.2 to 0 J/g. Mixograph water absorption of starch and gluten blends increased as the amylose content decreased. Generally, lower rheofermentometer dough height, higher gas production, and a lower gas retention coefficient were observed in starch and gluten blends with 12 or 18% amylose content compared with the regular starch and gluten blend. Bread baked from starch and gluten blends exhibited a more porous crumb structure with increased loaf volume as amylose content in the starch decreased. Bread from starch and gluten blends with amylose content of 19.2–21.6% exhibited similar crumb structure to that of bread with regular wheat starch which contained 24% amylose. Crumb moisture content was similar at 5 hr after baking but higher in bread with waxy starch than in bread without waxy starch after seven days of storage at 4°C. Bread with 10% waxy wheat starch exhibited lower crumb hardness values compared with bread without waxy wheat starch. Higher retrogradation enthalpy values were observed in breads containing waxy wheat starch (4.56 J/g at 18% amylose and 5.43 J/g at 12% amylose) compared with breads containing regular wheat starch (3.82 J/g at 24% amylose).     

Influence of High‐Temperature Drying on Structural and Textural Properties of Durum Wheat Pasta

Starch and protein are the main polymeric ingredients of pasta and they determine the structural and textural properties of cooked pasta. The present investigation sought better understanding of the impact of high‐temperature (HT) drying on the starch and the protein fraction, and their role in structure and texture of pasta. Durum wheat spaghetti was prepared in a pilot‐plant installation. The drying conditions were selected for the HT phase at 80 or 100°C applied at high, intermediate, or low product moisture content. Spaghetti dried at 55°C served as a reference sample. The color of dry pasta was measured and the changes in the starch and protein fractions were determined by protein solubility, light microscopy, confocal scanning laser microscopy (CSLM), cooking tests, and texture measurements. HT drying at 100°C and low product moisture promoted browning of pasta. At the molecular level, HT drying promoted protein denaturation. At the microscopic level, HT drying contributed to a better preservation of the protein network and reduced swelling of starch and disintegration of granules. At the macroscopic level, HT drying enhanced the firmness of cooked pasta and reduced surface stickiness. In general, the changes were more pronounced by increasing the drying temperature from 80 to 100°C and by shifting the HT phase from an early to a late stage of the drying process. The drying conditions are determinant for the phase morphology of protein and starch in cooked pasta which, in turn, govern the textural properties of pasta.     

养护龄期对改良膨胀土无侧限抗压强度试验的影响

以湖北省宜昌市某公路膨胀土为研究对象,分别采用不同掺量的石灰、水泥、粉煤灰、风化砂对膨胀土进行改良。在经过7,14和28d标准条件养生后,进行无侧限抗压强度试验。试验结果表明,上述4种材料均能有效地提高改良膨胀土的无侧限抗压强度,在最初的14d内,水泥改良膨胀土的强度增长较为明显,后期随着养护龄期的增长,无侧限抗压强度增长速率较缓慢;石灰改良膨胀土的无侧限抗压强度值随着养护龄期的增加,一直保持近似直线形的增长趋势;粉煤灰改良膨胀土的无侧限抗压强度亦随着养护龄期的增长而呈直线增长,但其值小于石灰改良膨胀土;养护龄期对风化砂改良膨胀土的无侧限抗压强度影响很小。     

Influence of Cooking Conditions on the Protein Matrix of Sorghum and Maize Endosperm Flours

To understand the influence of the sorghum and maize endosperm protein matrix honeycomb structure on starch hydrolysis in flours, three‐dimensional fluorescence microscopy was applied to floury and vitreous endosperm flours cooked under various conditions. Cooking caused the collapse and matting of the sorghum and maize vitreous endosperm matrices, with the effect being greater in sorghum. The effect of cooking was rather different in the floury endosperm in that the protein matrices expanded and broke up to some extent. These effects were a consequence of expansion of the starch granules through water uptake during gelatinization. Cooking in the presence of 2‐mercaptoethanol caused an expansion of the vitreous endosperm matrix mesh due to breakage of disulfide bonds in the protein matrix. Mercaptoethanol also caused an increase in the proportion of β‐sheet structure relative to α‐helical structure of the endosperm proteins. Increased energy of cooking caused collapse of the sorghum matrix. Disulfide bonding and an increase in β‐sheet structure occurred with cooking, with the increase in disulfide bonding being greatest in sorghum vitreous endosperm. The tendency for the sorghum protein matrix to collapse and mat more with cooking than the maize matrix appears to be due to greater disulfide bonding. This is responsible for the observed low starch digestibility of cooked sorghum flour as a result of the more disulfide‐bonded protein matrix limiting the expansion of the starch granules and hence amylase access.     

Physicochemical Properties of Rice Endosperm Proteins Extracted by Chemical and Enzymatic Methods

Rice proteins are nutritional, hypoallergenic, and healthy for human consumption. Efficient extraction with approved food‐grade enzymes and chemicals are essential for commercial production and application of rice protein as a functional ingredient. Rice endosperm proteins were isolated by alkali, salt, and enzymatic methods and evaluated for extractability and physicochemical properties. Alkali (RP_A) and salt (RP_S) methods extracted 86.9 and 87.3% of proteins with 65.9 and 58.9% yield, respectively. The enzymatic methods with Termamyl (RP_ET) and amylase S (RP_EA) extracted 85.8 and 81.0% proteins with 85.2 and 86.2% yield, respectively. Enthalpy values of RP_A (1.79 J/g), RP_S (1.22 J/g), RP_ET (nondetectable), and RP_EA (0.17 J/g), determined by differential scanning calorimetry, demonstrated that the varying level of denaturation of proteins depends on the method of extraction. Surface hydrophobicity data supported this observation. Alkali‐ and salt‐extracted proteins had higher solubility and emulsifying properties than those of enzyme‐extracted proteins. Comparatively, more favorable protein composition, lower surface hydrophobicity, higher solubility, and a lower degree of thermal denaturation of alkali‐ and salt‐extracted proteins contributed to higher emulsifying and foaming properties than those of enzyme‐extracted proteins; therefore, alkali‐ and salt‐extracted proteins can have enhanced functional use and a potential starting material for preparing tailored rice protein isolates.     

Hydrophobicity,Solubility, and Emulsifying Properties of Enzyme-Modified Rice Endosperm Protein

Rice endosperm protein was modified to enhance solubility and emulsifying properties by controlled enzymatic hydrolysis. The optimum degree of hydrolysis (DH) was determined for acid, neutral, and alkaline type proteases. Solubility and emulsifying properties of the hydrolysates were compared and correlated with DH and surface hydrophobicity. DH was positively associated with solubility of resulting protein hydrolysate regardless of the hydrolyzing enzyme, but enzyme specificity and DH interactively determined the emulsifying properties of the protein hydrolysate. The optimum DH was 6–10% for good emulsifying properties of rice protein, depending on enzyme specificity. High hydrophobic and sulfhydryl disulfide (SH-SS) interactions contributed to protein insolubility even at high DH. The exposure of buried hydrophobic regions of protein that accompanied high-temperature enzyme inactivation promoted aggregation and cross-linking of partially hydrolyzed proteins, thus decreasing the solubility and emulsifying properties of the resulting hydrolysate. Due to the highly insoluble nature of rice protein, surface hydrophobicity was not a reliable indicator for predicting protein solubility and emulsifying properties. Solubility and molecular flexibility are the essential factors in achieving good emulsifying properties of rice endosperm protein isolates.     

Glycosylation and Deamidation of Rice Endosperm Protein for Improved Solubility and Emulsifying Properties

Rice endosperm protein was prepared by alkali-extraction method and subsequently modified by controlled glycosylation (RP_Glu, RP_XG), deamidation (RP_DA), and enzymatic hydrolysis by alcalase (RP_Alc) methods. The RP_Glu and RP_XG were prepared by Maillard type glycosylation with D-glucose and xanthan gum, respectively. The glycosylation improved the emulsion activity (0.721) and stability (26.8 min) of the protein but did not show a substantial improvement in solubility (39.7%). The rice protein modified by controlled alkali-deamidation (RP_DA) showed highest solubility (68%), emulsion activity (0.776), and emulsion stability (24 min) among the three protein modification methods evaluated in this study. The alcalase treatment to 1.8% DH (RP_Alc) slightly improved solubility (33%), emulsion activity (0.468), and emulsion stability (17.5 min) compared with unmodified rice protein (RP), which had 18% solubility, 0.266 emulsion activity, and 14.7 min emulsion stability. The glycosylation and deamidation methods were more effective than the controlled enzymatic hydrolysis by alcalase in improving solubility and emulsifying properties of rice endosperm protein. Glycosylated and deamidated rice endosperm proteins can find application in enhancing emulsifying properties in suitable products.     

Influence of Starch and Gluten Characteristics on Rheological Properties of Wheat Flour Gel at Small and Large Deformation

Starch and gluten were isolated from 10 wheat cultivars or lines with varied amylose content. The rheological properties of 30% wheat flour gel, starch gel, and the gel of isolated gluten mixed with common starch were determined in dynamic mechanical testing under shear deformation, creep‐recovery, and compression tests under uniaxial compression. Variation of wheat samples measured as storage shear modulus (G′), loss shear modulus (G″), and loss tangent (tan δ = G″/G′) was similar between flour and starch gels and correlated significantly between flour and starch gel. The proportion of acetic acid soluble glutenin exhibited a significant relationship with tan δ of gluten‐starch mixture gel. The small difference in amylose content strongly affected the rheological parameters of flour gels in creep‐recovery measurement. Wheat flour gel with lower amylose content showed higher creep and recovery compliance that corresponded to the trend in starch gel. Compressive force of flour gel at 50 and 95% strain correlated significantly with that of starch gel. Gel mixed with the isolated gluten from waxy wheat lines appeared to have a weaker gel structure in dynamic viscoelasticity, creep‐recovery, and compression tests. Starch properties of were primarily responsible for rheological changes in wheat flour gel.     

Hydration Dynamics of Durum Wheat Endosperm as Studied by Magnetic Resonance Imaging and Soaking Experiments

The precise knowledge of the kinetics of water transport in durum wheat endosperm is a prerequisite for the optimization of wheat processing techniques like pasta dough mixing on a fundamental basis. Pieces of endosperm were cylindrically cut, prepared from durum wheat kernels, and used to study the water uptake by applying a gravimetric method and magnetic resonance imaging (MRI). The total water uptake of endosperm cylinders at different soaking times was determined by gravimetric soaking experiments and revealed a swelling limit of ≈40 g/100 g wb after 60 min. With these results it was possible to estimate an apparent diffusion coefficient of water in durum endosperm by using numerical simulation based on a diffusion model (D_25°C ~ 0.76 × 10^–10 m²/sec). MRI was used to quantify the water distribution in the endosperm cylinders over time at excess and limited water conditions. The calibration of MRI for the quantification of local and time‐dependent water contents was successful by correlating the spin‐spin relaxation time (T₂) with the water content of calibration samples at intermediate moisture levels (19–45 g/100 g wb). Water content maps were generated and showed the kinetics of water distribution inside the endosperm cylinders up to equilibrium conditions. The water uptake of the endosperm cylinders over time, as measured by MRI, fitted well to the water uptake as determined gravimetrically in soaking tests, which validated the applied MRI calibration and measurement procedures. The results allow the quantitative prediction of water transport properties of durum wheat endosperm during moistening procedures.     

Influence of Microwave Heating on Some Physicochemical Properties of Wheat Grain Harvested in Three Consecutive Years

Grain of winter wheat cv. Begra was investigated for changes in some physical and chemical properties resulting from direct influence of microwave heating on grain harvested in three subsequent generations of crops at Plant Breeding Station DANKO in Choryn, Poland. Wheat grain samples tested immediately after microwave treatment with the highest grain temperature at 79 and 98°C showed a statistically significant decrease in moisture content (MC), thousand kernel weight (TKW), single kernel weight (SKW), single kernel diameter (SKD), and hardness index (HI), with the exception of grain samples M‐120 and M‐180, respectively, where statistically significant increases in HI and SKD were observed. Indirect effect of microwaves caused statistically significant fluctuation of the total protein content (TPC), TKW, single kernel moisture content (SKM), HI, SKW, and SKD in all three wheat grain crops in relation to their control samples. This indicates that the studied physicochemical properties of grain were affected by microwave rays not only directly but also indirectly.