Enhanced selenium content in wheat grain by co-inoculation of selenobacteria and arbuscular mycorrhizal fungi: A preliminary study as a potential Se biofortification strategy

Cereal crops grown in southern Chilean Andisol provide suboptimal levels of this metalloid for human diet. Certain rhizosphere microorganisms, such as rhizobacteria and arbuscular mycorrhizal fungi can increase the selenium uptake in plants. The purpose of this study was to evaluate selenium acquisition by wheat plants through the co-inoculation of native selenobacteria strains (Stenotrophomonas sp. B19, Enterobacter sp. B16, Bacillus sp. R12 and Pseudomonas sp. R8), both individually and in mixture, as selenonanosphere source with one arbuscular mycorrhizal fungus (Glomus claroideum). Total selenium content in plant tissues and substrate was analyzed. According to our results, significant higher selenium content was found in inoculated plants in comparison to uninoculated controls (P ≤ 0.05). Independently of fungal presence, selenium content in grain from plants inoculated with Enterobacter sp. B16 (236 mg kg⁻¹) was higher than the rest of the strains (116–164 mg kg⁻¹). However, when plants were co-inoculated with a mixture of selenobacteria strains and G. claroideum, selenium content in grain was 23.5% higher (725 mg kg⁻¹) than non-mycorrhizal plants (587 mg kg⁻¹). The results suggest a synergistic effect between the selenobacteria mixture and G. claroideum associated to major biodiversity and demonstrate a great potential of these rhizosphere microorganisms for biofortification of cereals and its derivates.     

Variation in mineral micronutrient concentrations in grain of wheat lines of diverse origin

150 lines of bread wheat representing diverse origin and 25 lines of durum, spelt, einkorn and emmer wheat species were analysed for variation in micronutrient concentrations in grain. A subset of 26 bread wheat lines was grown at six sites or seasons to identify genetically determined differences in micronutrient concentrations. Substantial variation among the 175 lines existed in grain Fe, Zn and Se concentrations. Spelt, einkorn and emmer wheats appeared to contain higher Se concentration in grain than bread and durum wheats. Significant differences between bread wheat genotypes were found for grain Fe and Zn, but not Se concentration; the latter was influenced more by the soil supply. Grain Zn, but not Fe, concentration correlated negatively with grain yield, and there was a significant decreasing trend in grain Zn concentration with the date of variety release, suggesting that genetic improvement in yield has resulted in a dilution of Zn concentration in grain. Both grain Zn and Fe concentrations also correlated positively and significantly with grain protein content and P concentration, but the correlations with kernel size, kernel weight or bran yield were weak. The results from this study are useful for developing micronutrient biofortification strategies.     

Influence of wheat variety and dough preparation on FODMAP content in yeast-leavened wheat breads

FODMAPs are fermentable oligo-, di, and monosaccharides and polyols, which can have adverse effects on human health. Especially in individuals with gastrointestinal disorders such as irritable bowel syndrome, ingestion of FODMAPs may trigger or aggravate symptoms like abdominal pain, bloating, or diarrhea. Our objectives were to investigate the FODMAP content in the flour of 21 wheat varieties and in their 42 yeast-leavened breads prepared with a short (110 min) or a long dough fermentation (24 h), the latter according to a typical baker's recipe. Fructan, glucose, fructose and excess fructose were measured using enzymatic kits. On average, the breads of both dough fermentations had a FODMAP content reduced by > 65% compared to that of the whole grain wheat flour. Average FODMAP content of both dough fermentations was 0.22 g per 100 g fresh bread. FODMAP content tended to be lower in the long compared to the short dough fermentation, however, the difference was not statistically significant. We also found that the 21 wheat varieties differed up to five times in their potential to form FODMAPs in bread. In conclusion, the choice of a low fructan wheat variety coupled with long dough fermentation with sourdough and yeast is best to minimize FODMAPs in breads.     

喷施硒对大豆品质和大豆食品硒水平的影响

用田间试验研究喷施亚硒酸钠对大豆品质和大豆食品硒水平的影响。结果表明，叶面喷施亚硒酸钠浓度小于400mg/L对产量无显著影响，亚硒酸的浓度大于600mg/L，大豆产量显著下降。喷施亚硒酸钠显著提高大豆脂肪含量，特别是亚油酸含量提高1％左右，但对大豆蛋白质含量和氨基酸组成影响不显著。利用富硒大豆生产的大豆食品含硒量显著提高，大豆分离蛋白含硒量为7．487μg/g，豆奶粉为1．023μg/g，豆芽为1．033μg/g,白豆腐干为1.412μg/g.大豆分离蛋白可作为富硒功能食品的有机硒源，豆渣可作为动物饲料添加剂。     

Effect of temperature, time and wheat gluten moisture content on wheat gluten network formation during thermomolding

A plastic-like material can be obtained by thermomolding wheat gluten protein which consists of glutenin and gliadin. We studied the effect of molding temperature (130-170 °C), molding time (5-25 min) and initial wheat gluten moisture content (5.6-18.0%) on the gluten network. Almost no glutenins were extractable after thermomolding irrespective of the molding conditions. At the lowest molding temperature, the extractable gliadin content decreased with increasing molding times and moisture contents. This effect was more pronounced for the α- and γ-gliadins than for the ω-gliadins. Protein extractabilities under reducing conditions revealed that, at this molding temperature, the cross-linking was predominantly based on disulfide bonds. At higher molding temperatures, also non-disulfide bonds contributed to the gluten network. Decreasing cystine contents and increasing free sulfhydryl and dehydroalanine (DHA) contents with increasing molding temperatures and times revealed the occurrence of β-elimination reactions during thermomolding. Under the experimental conditions, the DHA derived cross-link lanthionine (LAN) was detected in all gluten samples thermomolded at 150 and 170 °C. LAN was also formed at 130 °C for gluten samples containing 18.0% moisture. Degradation was observed at 150 °C for samples thermomolded from gluten with 18.0% moisture content or thermomolded at 170 °C for all moisture contents.     

Impact of water content on the solubilisation of arabinoxylan during xylanase treatment of wheat bran

Arabinoxylan (AX) has a major impact on the functional properties of wheat bran, and it has been shown that technological properties of bran can be improved by using endoxylanases. Enzymatic treatments are typically conducted at high water content. However, in industrial applications, low water content may be advantageous, especially when targeting dry end products. The aim of the study was to examine the impact of water content, ranging from 20 to 90%, on the efficiency of endoxylanase treatment of wheat bran. Interestingly, AX solubilisation was highest at the water contents of 40 and 90%. At water contents 50–80%, AX solubilisation was lower than at 40 and 90%. Furthermore, at low water content, less depolymerisation was detected. At water content of 40%, the bran-water mixture was transformed from powder-like into compact mass. Probably the compact consistency of the material enhanced AX solubilisation by increased breakdown of bran cell walls due to shear forces or via enhanced enzyme binding to the substrate. The results show that solubilisation of bran AX can also be efficiently performed at low water content.     

Arabinoxylan and hydroxycinnamate content of wheat bran in relation to endoxylanase susceptibility

Hydroxycinnamate and protein contents and monosaccharide composition were determined for 11 industrial wheat (Triticum aestivum) brans and related to the susceptibility of their arabinoxylans (AX) to enzymatic degradation. There was significant variation in carbohydrate, A/X ratio, protein, hydroxycinnamic acid and diferulic acid (DiFA) content among the wheat brans. In addition, a strong correlation was found between AX and ferulic acid contents. Brans were extracted with water followed by a dry-thermal treatment to remove 90% starch and to inactivate endogenous enzymes and proteinaceous inhibitors. Treated brans were compared with respect to AX degradation by a family 11 xylanase. Digestion with xylanase had a strong impact on the chemical composition of the residual bran. The A/X ratio changed from 0.60 to 1.07. The solubilised AX had an A/X ratio of 0.32. The A/X ratio of enzyme-depleted bran was negatively correlated with the loss of AX. Total DiFA in destarched brans was negatively correlated with the amount of soluble AX. These relationships indicate that structural features of AX and the extent of its cross-linking in the cell walls of the bran tissues influence its susceptibility to xylanase treatment. Thus, the amount of enzyme-solubilised AX was not directly related to the content of AX in the destarched bran. However, brans differed in their susceptibility to xylanase attack.     

Sulfur fertilization improves nitrogen use efficiency in wheat by increasing nitrogen uptake

Nitrogen (N) fertilization plays a central role for improving yield in wheat and high N use efficiency (NUE) is desired to protect ground and surface waters. Several studies showed that sulfur (S) fertilization may increase NUE, but no attempts have been made to explain whether this increase is due to greater recovery efficiency (RE), an enhanced internal efficiency (IE) or by an improvement of both efficiencies. The aim of this study was to analyze the effects of different N and S fertilizer rates, and their interaction on N uptake, its partition at maturity, NUE and its main components. Field experiments were carried out during two consecutive growing seasons in the Argentinean Pampas using a single bread-wheat genotype grown under different combinations of N and S fertilizer rates. Additional experiments were performed in farmer fields using N and S fertilization evaluating different genotypes in order to analyze the components of NUE in other environmental conditions. Plant N uptake increased linearly in response to N addition until rates of ca. 80 kg N ha⁻¹. Sulfur addition showed no effect at the lowest N fertilizer rate, but N uptake was increased when S was applied at the highest N rate, revealing a synergism between both nutrients. At the lowest S rate RE was 42%, and increased to 70% when S fertilizer was added. No changes in IE in response to S fertilization were observed. These results were also observed in farmer field experiments, in genotypes that showed different IE. This study showed that S addition increased NUE mainly by increasing the N recovery from the soil. Thus, the concurrent management of N and S is important for reducing the potential pollution of residual soil nitrate by increasing N recovery from the soil while sustaining high nitrogen use efficiency.     

Effect of germination and subsequent oven-drying on folate content in different wheat and rye cultivars

Cereals are recognised as an important food source of folate, and germinated cereals are reported to contain even more folate. This study examined the effects of germination and oven-drying on folate content in different wheat and rye cultivars. The native folate content in four wheat cultivars ranged from 23 to 33 μg/100 g dry matter (DM) and that in six rye cultivars from 31 to 39 μg/100 g DM. Mean folate content in rye was 25% higher than in wheat. Germination of both cereals resulted in a 4- to 6-fold increase in folate content, depending on cultivar and duration of germination. The highest folate content in both cereals was found after 96 h of germination and was 181 μg/100 g DM for cv. Kaskelott (rye) and 155 μg/100 g DM for cv. Kosack (wheat). Germination increased the amount of 5-CH₃–H₄folate in both cereals from 45 to 75%. Oven-drying of germinated wheat grains (for 48 and 72 h) at 50 °C did not affect the folate content. In conclusion, germination increases the folate content in wheat and rye cultivars, while subsequent oven-drying does not affect the folate content. Germination can therefore be recommended for producing bakery ingredients with increased folate content.     

硒对花生抗氧化作用的初步研究

通过对花生叶面喷施不同浓度的亚硒酸钠，初步研究了硒对花生抗氧化作用的影响，结果表明，10～60mg/LSe使叶绿素的含量和POD活性高于对照，且随着硒浓度的增加，它们的含量也相应增加;而MDA低于对照，随着硒用量的增加而下降。在Se浓度达到90 mg/L时，叶绿素含量、POD活性呈下降趋势而MDA含量则升高。10～90mg/LSe使CAT和SOD低于对照，先随硒浓度的增加而下降，在高浓度硒时又上升。     

Reducing the reliance on nitrogen fertilizer for wheat production

All crops require nitrogen (N) for the production of a photosynthetically active canopy, whose functionality will strongly influence yield. Cereal crops also require N for storage proteins in the grain, an important quality attribute. Optimal efficiency is achieved by the controlled remobilization of canopy-N to the developing grain during crop maturation. Whilst N will always be required for crop production, targeting efficient capture and use will optimise consumption of this valuable macronutrient. Efficient management of N through agronomic practice and use of appropriate germplasm are essential for sustainability of agricultural production. Both the economic demands of agriculture and the need to avoid negative environmental impacts of N-pollutants, such as nitrate in water courses or release of N-containing greenhouse gases, are important drivers to seek the most efficient use of this critical agronomic input. New cultivars optimised for traits relating to N-use efficiency rather than yield alone will be required. Targets for genetic improvement involve maximising capture, partitioning and remobilization in the canopy and to the grain, and yield per se. Whilst there is existing genetic diversity amongst modern cultivars, substantial improvements may require exploitation of a wider germplasm pool, utilizing land races and ancestral germplasm.     

Risk assessment of pesticide residues in South African raw wheat

The presence of pesticide residues in wheat produced and imported in South Africa was determined and their health risks assessed. Pesticides were detected in all local (median = 1, range: 1–3, n = 71) and imported (median = 1, range: 1–6, n = 13) samples. Multiple pesticides (>1 pesticide) were detected in about 30% local samples and 39% imported samples. Eight different pesticides were detected in total. The most frequently detected pesticides were mercaptothion (99%), permethrin (19%) and chlorpyrifos (17%). Nine (11%) samples exceeded the EU wheat MRL for permethrin (0.05 mg/kg) which included 7 (10%) local samples and 2 (15%) imported samples. The highest fenitrothion level (0.65 mg/kg) corresponds to an intake that was below but near the estimated short-term safety threshold. The results call for an investigation into the levels of pesticide residues in cereal-based food and for tighter regulation and regular monitoring by government and industry.     

Rabadi fermentation of wheat: Changes in phytic acid content andin vitro digestibility

Fermentation of raw as well as autoclaved wheat flour with buttermilk at 30, 35 and 40°C for 6, 12, 18, 24 ad 48h significantly decreased the level of phytic acid; maximum decrease was observed at 40°C for 48h. Starch as well as protein digestibility (in vitro) improved with an increase in temperature and period of fermentation. Phytic acid had a significant (P<0.05) negative correlation with digestibility (in vitro) of both starch and protein ofrabadi.     

叶面喷硒对小麦抗氧化性能及籽粒硒含量的影响

为探讨大田条件下硒对小麦抗氧化性能及籽粒中硒含量的影响．以亚硒酸钠（Na2SeO3）和富硒增产素为硒源，从硒的用量、形态和喷施时间三个方面进行了分析。结果表明，喷硒后谷胱甘肽过氧化物酶（GSH-Px）活性显著提高；小麦根系活力和旗叶游离脯氨酸含量明显高于对照；小麦籽粒硒含量最高为对照的3．3倍，各处理均表现出增产趋势，最高增产5．1％。富硒增产素喷施效果优于亚硒酸钠．孕穗期喷施比灌泉期喷施效果好。     

Genotypic variation in wheat grain fructan content revealed by a simplified HPLC method

Fructans are prebiotics, with potentially beneficial effects on human health. This study aimed to examine genetic variation in wheat grain fructan content using a simplified analytical method. The method involves extracting fructans from wheat grain followed by enzymatic hydrolysis to break down fructans into monosaccharides that can then be quantitatively measured by anion-exchange liquid chromatography coupled with pulsed amperometric detection. The modified procedure is reliable and allows the handling of large numbers of flour samples at a low cost, and could therefore be useful for assessing large numbers of wheat breeding lines. Using this method, grain samples taken from 19 bread wheat cultivars and breeding lines grown in both glasshouse and the field were analysed for grain fructan content. In addition, grain samples of 29 international wheat landraces and 14 new wheat breeding lines from the International Maize and Wheat Improvement Center (CIMMYT) were surveyed for their fructan contents. There was significant genotypic variation among these materials, with grain fructan content ranging from 0.7 to 2.9% of grain dry weight. There was no evidence of strong genotype-by-environment interaction; the fructan contents of field-grown grain samples were positively correlated (r = 0.83) with those of glasshouse-grown samples of the same cultivars. It should therefore be possible to investigate the genetic control of variation for this trait using the simplified HPLC method and to select effectively for increased grain fructan content in wheat breeding.     

Effects of drought and the presence of the 1BL/1RS translocation on grain vitreosity, hardness and protein content in winter wheat

Grain texture is an important component of end-use quality in wheat. The effects of water availability on the components of texture; vitreosity, determined using a Light Transflectance meter (LTm), grain hardness measured using the single-kernel characterisation system (SKCS), and protein content, were studied in field experiments of winter wheat in the UK in 2001/2002 and 2002/2003. Experiments were grown on a drought prone soil and employed a mapping population of 46 doubled haploid (DH) lines and their parents, Beaver (+1BL/1RS, soft wheat) and Soissons (1B, hard wheat). The results showed that drought increased hardness in both seasons, but the effect was never sufficient to move a line from the soft class into the hard class. Puroindoline (PIN)-a:b peak height ratio explained ca. 78% of the variation in hardness, and drought also appeared to increase the amounts of PINs in the grain. Minor quantitative trait loci (QTLs) were found for hardness on chromosomes 2A, 2D, 3A and 6D, also associated with QTLs for PINs. Vitreosity also increased in response to drought in both seasons. Variation in vitreosity explained 7–11% of the overall variation in texture within a hardness class, with hardness increasing on average by 2.2 SKCS units for each 10% increase in the proportion of vitreous grains. The relationship between vitreosity and protein content was poor, despite the fact that protein content also increased in response to drought. Minor QTLs associated with both protein content and vitreosity were found on chromosomes 1B, 4D and 5D. A minor QTL for vitreosity was also found on chromosome 2D. However, there appeared to be no direct relationship between alleles at the Ha locus, the gene which controls the difference between hard and soft wheats, and vitreosity. A positive relationship between the presence of the 1BL/1RS translocation and the proportion of vitreous grains was identified, suggesting that vitreosity was strongly linked to changes in protein quality.     

叶面喷施硒酸钠对不同小麦品种(系)籽粒硒及其他矿质元素含量的影响

为了解叶面喷施硒酸钠对不同小麦品种(系)籽粒硒含量及其他矿质元素的影响,对114个不同小麦品种(系)进行叶面喷施硒酸钠,试验设4个梯度,分别为0 mg·kg~(-1)(CK)、100 mg·kg~(-1)(Se10)、200mg·kg~(-1)(Se20)、300mg·kg~(-1)(Se30),利用离子发射光谱-原子吸收仪测定了籽粒硒、钙、镁、铜、铁、锰、锌、硫含量。结果表明,叶面喷施硒酸钠可以提高小麦籽粒的硒含量,增幅因品种(系)而异;CK、Se10、Se20及Se30处理下,籽粒的总硒含量分别为1.54、5.70、10.01和13.10mg·kg~(-1)。籽粒中不同矿物质元素对叶面喷施硒酸钠的响应不同;籽粒中硒与其他元素的积累既有协同也有拮抗作用,因元素种类、小麦品种(系)和施硒量而异。总体而言,高浓度硒处理降低了籽粒中钙、镁、铜、铁、锰和硫的含量,但提高了锌的含量。     

Fractionation of wheat and wheat flour into starch and gluten: overview of the main processes and the factors involved

The starch and gluten components of wheat flour or whole wheat kernels can be separated by a number of industrial processes. This review provides a summary of these processes from both starting materials. The wheat constituents of importance in the fractionation processes are briefly introduced, and the different fractionation processes described with emphasis on the parameters affecting the separation, such as flour composition, mixing and washing water, processing aids (with an emphasis on enzymes) and kernel pre-treatment (pearling) in the case of flour fractionation and steeping conditions and processing aids in the case of whole wheat. Although fractionation of flour is the basis for the current industrial processes, starch yields are impaired by starch damage as a result of milling and loss of starch to milling streams. On the other hand fractionation of whole kernels often leads to impaired gluten production as a result of harsh process conditions which ‘devitalise’ the gluten.