Determination of selenium in bread-wheat samples grown under a Se-supplementation regime in actual field conditions

Selenium in Wheat from Farming to Food

Selenium (Se) plays an important role in human health. Approximately 80% of the world's population does not consume enough Se recommended by the World Health Organization. Wheat is an important staple food and Se source for most people in the world. This review summarizes literature about Se from 1936 to 2020 to investigate Se in wheat farming soil, wheat, and its derived foods. Se fortification and the recommended Se level in wheat were also discussed. Results showed that Se contents in wheat farming soil, grain, and its derived foods around the world were 3.8-552 μg kg^-1 (mean of 220.99 μg kg^-1), 0-8270 μg kg^-1 (mean of 347.30 μg kg^-1), and 15-2372 μg kg^-1 (mean of 211.86 μg kg^-1), respectively. Adopting suitable agronomic measures could effectively realize Se fortification in wheat. The contents in grain, flour, and its derived foods could be improved from 93.94 to 1181.92 μg kg^-1, from 73.06 to 1007.75 μg kg^-1, and from 86.90 to 587.61 μg kg^-1 on average after leaf Se fertilizer application in the field. There was a significant positive correlation between the Se content in farming soil and grain, and it was extremely the same between the foliar Se fertilizer concentration rate and the grain Se increased rate. The recommended Se fortification level in cultivation of wheat in China, India, and Spain was 18.53-23.96, 2.65-3.37, and 3.93-9.88 g hm^-2, respectively. Milling processing and food type could greatly affect the Se content of wheat-derived food and should be considered seriously to meet people's Se requirement by wheat.

Fate of selenium in biofortification of wheat on calcareous soil: an isotopic study

Selenium (Se) biofortification of staple cereal crops can improve the Se nutritional status of populations. A field trial employing an enriched stable isotope of Se (77Se) was undertaken over three consecutive cropping seasons in a coarse-textured, calcareous soil in Gilgit-Baltistan, Pakistan. The objectives were to (1) assess the feasibility and efficiency of Se biofortification, (2) determine the fate of residual Se, and (3) assess the consequences for dietary Se intake. Isotopically enriched 77Se (77SeFert) was applied, either as selenate or as selenite, at three levels (0, 10, and 20 g ha-1) to a wheat crop. Residual 77SeFert availability was assessed in subsequent crops of maize and wheat without further 77SeFert addition. Loss of 77SeFert was c.35% by the first (wheat) harvest, for both selenium species, attributable to the practice of flood irrigation and low adsorption capacity of the soil. No 77SeFert was detectable in subsequent maize or wheat crops. The remaining 77SeFert in soil was almost entirely organically bound and diminished with time following a reversible (pseudo-)first-order trend. Thus, repeat applications of Se would be required to adequately biofortify grain each year. In contrast to native soil Se, there was no transfer of 77SeFert to a recalcitrant form. Grain from control plots would provide only 0.5 µg person-1 day-1 of Se. By contrast, a single application of 20 g ha-1 SeVI could provide c. 47 µg person-1 day-1 Se in wheat, sufficient to avoid deficiency when combined with dietary Se intake from other sources (c. 25 µg day-1).

Effects of selenium on macro- and micro nutrients and selected qualitative parameters of oat (Avena sativa L.)

The article deals with the effect of foliar Se application on macro-and micro-elements and selected quantitative parameters (the content of ash, starch, and fat) in oat grains. The three-year experiments were carried out on Research and Breeding Station Vígľaš – Pstruša in the years 2014, 2015, 2016. The used oat variety was Valentin. The experiment was performed by a block method within a parcel size of 10 square meters (8 x 1.25 m) with the span of rows amounting to 0.125 m in four replications. Alfalfa was grown as forecrop. A potato and wheat production area (III-C2) with a height of 375 m above the sea level. The experimental area is characterized by warm, slightly wet weather with an average annual temperature of 7.8 °C and average annual precipitations of 666 mm. Basic fertilizing was planned before the sowing in the form of 100 kg of Ammonium nitrate containing dolomite (27% N), 100 kg of 60% KCl (60% of K2O), and100 kg of MAP (Monoammonium phosphate 12% N and 52% P2O5). Selenium was foliar applied in doses 25 g and 50 g Se per hectare in a solution form of sodium selenate (Na2SeO4). The harvest was realized by a small plot harvester in BBCH 91. The results of the experiments showed a statistically non-significant effect on microelements and most macroelements. Only sulfur content in oat grains was statistically significantly influenced by Se foliar treatment. The contents of ash, starch, and fat in oat grains were monitored, which showed statistically significant effect only in fat. Se content in grains showed a statistically significant increase by both Se foliar treatments.

Translocation of elements and sugars in wheat genotypes at vegetative and generative stages under continuous selenium exposure

BACKGROUND

Biofortification with selenium (Se) elevates its concentration in feed and fodder plants and helps to prevent health problems in animals and humans. The aim of this study was to describe Se-induced modifications in the accumulation of elements important for the proper functioning of wheat, one of the most popular cereals. The presence of Se correlated with carbohydrate synthesis and electron paramagnetic resonance (EPR). This explained the mechanisms of Se's antioxidant activity.

RESULTS

Selenium accumulation in vegetative and generative leaves, and in the grains of three wheat genotypes (cv. Parabola, cv. Raweta and cv. Manu), differing in their stress tolerance and grown hydroponically in the presence of 10 or 20 μM Na₂ SeO_4, , was proportional to its content in the medium. Stronger Se accumulation was typical of a stress-sensitive genotype. Selenium generally promoted the uptake of macronutrients and micronutrients but their distribution depended on tissue and genotype. Changes in the Se-induced EPR signals of paramagnetic metals and organic radicals corresponded with stress tolerance of the tested genotypes.

CONCLUSIONS

Se application increased the accumulation of nutrients and carbohydrates that are vital for proper plant growth and development. Accelerated uptake of molybdenum (Mo), an element improving dietary properties of grains, may be an additional advantage of Se fertilization. The mechanisms of Se-induced changes in removing Mn and iron (Fe) ions from macromolecules may be one of the factors that differentiate plant tolerance to oxidative stress. © 2019 Society of Chemical Industry.

Preparation and characterization of a laboratory scale selenomethionine-enriched bread. Selenium bioaccessibility

This study focuses on the preparation at lab scale of selenomethionine-enriched white and wholemeal bread. Selenium was supplemented either by adding selenite directly to the dough or by using lab-made selenium-enriched yeast. The best results were obtained when using fresh selenium-enriched yeast. The optimum incubation time for selenomethionine-enriched yeast preparation, while keeping formation of selenium byproducts to a minimum, was 96 h. Selenium content measured by isotope dilution analysis (IDA)-ICP-MS in Se-white and Se-wholemeal bread was 1.28 ± 0.02 μg g–1 and 1.16 ± 0.02 μg g–1 (expressed as mean ± SE, 3 replicates), respectively. HPLC postcolumn IDA-ICP-MS measurements revealed that selenomethionine was the main Se species found in Se-enriched bread, which accounted for ca. 80% of total selenium. In vitro gastrointestinal digestion assay provided selenium bioaccessibility values of 100 ± 3% and 40 ± 1% for white and wholemeal Se-enriched bread, respectively, being selenomethionine the main bioaccessible Se species in white bread, while in wholemeal bread this compound was undetectable.

Microbial-enhanced Selenium and Iron Biofortification of Wheat (Triticum aestivum L.)--Applications in Phytoremediation and Biofortification

Selenium (Se) is an essential trace element for humans and other mammals. Most dietary Se is derived from crops. To develop a Se biofortification strategy for wheat, the effect of selenate fertilization and bacterial inoculation on Se uptake and plant growth was investigated. YAM2, a bacterium with 99% similarity to Bacillus pichinotyi, showed many plant growth promoting characteristics. Inoculation with YAM2 enhanced wheat growth, both in the presence and absence of selenate: YAM2-inoculated plants showed significantly higher dry weight, shoot length and spike length compared to un-inoculated plants. Selenate also stimulated wheat growth; Un-inoculated Se-treated plants showed a significantly higher dry weight and shoot length compared to control plants without Se. Bacterial inoculation significantly enhanced Se concentration in wheat kernels (167%) and stems (252%), as well as iron (Fe) levels in kernels (70%) and stems (147%), compared to un-inoculated plants. Inoculated Se-treated plants showed a significant increase in acid phosphatase activity, which may have contributed to the enhanced growth. In conclusion; Inoculation with Bacillus sp. YAM2 is a promising Se biofortification strategy for wheat and potentially other crops.

Characterization of selenium-enriched wheat by agronomic biofortification

Agronomic biofortification of staple crops is an effective way to enhance their contents in essential nutrients up the food chain, with a view to correcting for their deficiencies in animal or human status. Selenium (Se) is one such case, for its uneven distribution in the continental crust and, therefore, in agricultural lands easily translates into substantial variation in nutritional intakes. Cereals are far from being the main sources of Se on a content basis, but they are likely the major contributors to intake on a dietary basis. To assess their potential to assimilate and biotransform Se, bread and durum wheat were enriched with Se through foliar and soil addition at an equivalent field rate of 100 g of Se per hectare (ha), using sodium selenate and sodium selenite as Se-supplementation matrices, in actual field conditions throughout. Biotransformation of inorganic Se was evaluated by using HPLC-ICP-MS after enzymatic hydrolysis for Se-species extraction in the resulting mature wheat grains. Selenomethionine and Se(VI) were identified and quantified: the former was the predominant species, representing 70-100 % of the total Se in samples; the maximum amount of inorganic Se was below 5 %. These results were similar for both supplementation methods and for both wheat varieties. Judging from the present results, one can conclude that agronomic biofortification of wheat may improve the nutritional quality of wheat grains with significant amounts of selenomethionine, which is an attractive option for increasing the Se status in human diets through Se-enriched, wheat-based foodstuff.

Determination of trace amounts of Se(IV) by hydride generation atomic fluorescence spectrometry after solid-phase extraction using magnetic multi-walled carbon nanotubes

A sensitive and simple method using magnetic multi-walled carbon nanotubes, as an adsorbent, has been successfully developed for extraction and preconcentration trace amounts of Se(IV) with detection by hydride generation atomic fluorescence spectrometry. The prepared nanoparticles were confirmed by Fourier transform infrared spectra, X-ray diffraction spectrometry, vibrating sample magnetometry, and transmission electron microscopy. These magnetic nanocomposites can be easily dispersed in aqueous samples and retrieved by the application of external magnetic field via a piece of permanent magnet. The main factors affecting the signal intensity such as sample pH value, adsorbent amount, eluent concentration and volume, sample volume, and coexisting ions have been investigated and established. The absorbent could be repeatedly used at least 100 times. The enhancement factor of the proposed method for Se(IV) was 100. The method had a linear calibration plot in the range from 0.05 to 10.0 μg L(-1) with a standard deviation of 2.3% at 0.5 μg L(-1) (n=11). The limit of detection was as low as 0.013 μg L(-1). Accuracy of the method was evaluated by the analysis of water samples and certified reference materials.