In vitro dephytinization and bioavailability of essential minerals in several wheat varieties

Twelve wheat varieties were studied for their phytic acid, calcium, iron, zinc, copper and phosphorus contents, which respectively ranged between 114–166, 25.1–53.5, 3.41–5.55, 0.71–3.00, 0.65–1.32 and 298–314 mg/100 g. The molar ratios as Ca:Phy, Phy:Fe, Phy:Zn, Phy:Cu were found to be 0.14–0.29, 1.96–3.86, 5.11–20.5 and 13.0–23.9, respectively. Significant dephytinization, ranging between 35.3 and 69.3% in different varieties, was achieved on exogenous enzymatic treatment. Enzymatic dephytinization in the in vitro simulated gastrointestinal digestion resulted in significant increase in the bioavailability of essential minerals. The increase in bioavailability of calcium, iron, zinc and copper on exogenous enzymatic dephytinization ranged between, respectively (x-folds): 1.30–1.96, 1.11–1.52, 1.22–1.78 and 1.11–1.73.     

Influence of baking and in vitro digestion on steryl ferulates from wheat

So far, data on absorption and metabolism of steryl ferulates from edible sources is scarce. Therefore, the impact of enzyme-aided baking and in vitro digestion was examined in this study. Wheat flours and wheat breads were subjected to a static in vitro digestion model and changes in the contents of steryl ferulates and free sterols (possible hydrolysis products of steryl ferulates) were monitored. Baking degraded steryl ferulates at a similar rate in all types of breads (43–47%) compared to the corresponding flours, while baking induced changes in free sterols showed no clear pattern. In vitro digestion provoked five folds lower content of steryl ferulates in flours than in breads and it also resulted in significant free sterol accumulation. Interestingly, bioaccessibility (0.01–0.25%) was not influenced by the cereal matrix. The four steryl ferulate species, which were detected in wheat, showed similar hydrolysis rates during digestion. As baking had a significant impact on the steryl ferulate content of wheat, we suggest that both raw and processed sources should be considered further in vitro, animal or human trials, when studying the metabolic fate of steryl ferulates.     

Effect of wheat bran addition on in vitro starch digestibility,physico-mechanical and sensory properties of biscuits

Biscuits contain high amount of fat and sugar thus having high calorie but low nutrient density. Wheat bran is a good source of dietary fibre (DF) and protein and is thus a good candidate for nutritional enrichment of cereal foods. The aim of this study was to understand the effect of bran incorporation and particle size reduction on biscuit microstructure, texture and in vitro starch digestibility. Five different biscuits containing 5–15% DF were produced. Two different particle sized wheat brans were used: coarse (450 μm) and fine (68 μm). Bran particle size reduction increased the elastic modulus and hardness of biscuits. Biscuits containing fine bran had visually more compact structure without any surface or internal defects than those with coarse bran. Fine bran containing sample had the highest hardness value. Sensory evaluation showed that roughness and breakdown of biscuits in the mouth was significant for the coarse bran with highest level of bran addition. The instrumental elastic modulus, stress and hardness were closely related to sensory hardness and strength to break. Increasing DF content from 5 to 15% increased hydrolysis index by 16%, from 32 to 37.     

In vitro starch digestibility and pasting properties of germinated brown rice after hydrothermal treatments

Germinated brown rice (GBR) recently has received renewed attention due to its enhanced nutritional value. Pasting properties and in vitro starch digestibility of GBR were examined before and after hydrothermal treatments. Steeping in water (30 °C, 24 h) raised the moisture content and germination percentage of brown rice. Pasting viscosity was substantially decreased but gelatinization temperatures and enthalpy were decreased only marginally by germination (30 °C, 48 h). However, annealing (50 °C, 24 h) and heat-moisture treatment (100 °C, 1 h at 30% moisture) after germination resulted in increased pasting viscosity and gelatinization temperatures. The hydrothermal treatments, however, induced browning reactions to darken the flour of GBR. The digestibility of starch in brown rice was increased by germination. The contents of rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS) in the cooked brown rice were 47.3%, 40.8%, and 11.9%, respectively, but changed to 57.7%, 39.1%, and 3.2%, respectively upon germination. The hydrothermal treatments, however, decreased the digestibility of starch in GBR. The heat-moisture treatment decreased the RDS content in GBR near to that of native brown rice. The digestibility and physical properties of brown rice can be controlled by germination and hydrothermal treatments.     

Bioavailability of Calcium,Iron and Zinc Fortified Whole Wheat Flour Chapatti

The bioavailability and interactive effects of calcium, iron and zinc fortified whole wheat flour chapattis on female Sprague–Dawley albino rats were determined. The whole wheat flour was fortified with CaCO₃, FeSO₄ and ZnSO₄ at 1000, 40 and 20 mg/kg, respectively and fed to 64 female Sprague–Dawley rats for 4 weeks. Retention of Ca, Fe and Zn was determined in plasma, femur and liver tissues. Ca levels in plasma and liver did not alter significantly while the Ca retention in femur changed significantly with the change in fortificants. The calcium retention was higher in the femur of rats fed on the diet supplemented with Ca + Zn (221 ± 13.61 mg/g) than the rats fed on the diet supplemented with Ca + Fe (219 ± 18.92 mg/g). The iron in plasma, liver and femur ranged from 2.19 ± 0.11 to 2.77 ± 0.10 μg/ml, 203.5 ± 13.24 to 251.5 ± 17.19 μg/g and 43.5 ± 1.05 to 52 ± 2.07 μg/g while zinc content ranged from 1.31 ± 0.089 to 1.55 ± 0.114 μg/ml, 89.5 ± 3.41 to 132 ± 6.10 μg/g and 175 ± 8.29 to 191 ± 10.85 μg/g, respectively. The minerals interacted with each other resulting in decrease of bioavailability among each other. The absorption was higher in the rats fed on fortified diet than those fed on unfortified chapatti diet. Hence, it is concluded that fortification of whole wheat flour is feasible to overcome the Ca, Fe and Zn malnutrition in the vulnerable groups.     

Improvement in HCl-extractability of minerals in home made weaning foods

Three weaning foods were formulated from locally available cereals and pulses such as rice (Oryza sativa), kangini (Setaria italica), sanwak (Echinochloa frumentacea), green gram (Vigna radiata) and jaggery. Cereals and pulses were mixed in the proportion of 7:3. Nutrient composition of developed weaning foods was within range prescribed by Indian Standard Institute and was found to be acceptable. Roasting was the processing technique employed in developing weaning foods which resulted in significant increase in HC1-extractable minerals, an index of their bioavailability to humans. The higher HC1-extractability of the minerals may be ascribed to the decreased phytic acid in the processed home made weaning foods.     

Effect of milling,pasta making and cooking on minerals in durum wheat

The effect of technological processing on the contents of eight minerals – i.e., calcium, copper, iron, magnesium, phosphorous, potassium, selenium, and zinc – was investigated in pasta making. Milling of durum wheat as well as pasta making were carried out in a pilot plant by using three different grain samples. Pasta samples purchased on the market were also surveyed to gain information on the mineral content of commercial products. The effect of cooking was also investigated in order to determine the retention of the selected elements in the final ‘ready-to-eat’ product. Analyte concentrations in whole grains, semolina, pasta and cooked pasta were determined by inductively coupled plasma-mass spectrometry.     

Effects of specific domains of high-molecular-weight glutenin subunits on dough properties by an in vitro assay

An in vitro system for incorporating bacterially produced high-molecular-weight glutenin subunits (HMW-GS) into doughs was used to study the effects of specific domains of the HMW-GS. Synergistic effects of incorporating into doughs both the Dx5 and Dy10 subunits are localized to the N-terminal domains. All single and pair-wise combinations of original subunits and hybrid subunits with their N-terminal domains exchanged between Dx5 and Dy10 finds three classes of respondents: the greatest response is when the N-termini of both Dx5 and Dy10 are present, followed by presence of the Dx5 N-terminus alone, and the least response by the presence of the Dy10 N-terminus alone. In addition, studies of Dx5 variants possessing repetitive domains of different length and composition find evidence that the length of the HMW-GS repetitive domain is important for dough properties and that the exact composition of the repeat domain has a detectible, though lesser contribution. Finally, in this experimental system, the Glu-D1 x- and y-subunits function in the mixing experiments as if they were a fused dimer, although the exact molecular basis of the effect is not known.     

Dephytinization of wheat bran by fermentation with bakers' yeast,incubation with barley malt flour and autoclaving at different pH levels

Wheat bran is an important source of dietary fiber but also contains considerable amounts of phytic acid, which is known to impair mineral absorption. The present study was conducted to investigate the phytic acid reduction in coarse and fine wheat bran by fermentation with the different levels of bakers' yeast (3, 6 and 9%) for 8 h at 30 °C, incubation with the different levels of barley malt flour (2.5, 5.0, 7.5 and 10.0%) for 8 h at pH 5.2 and 55 °C, and autoclaving at the different pH levels (pH 5.0, 4.5, 4.0 and 3.5) adjusted with acetic acid for 2 h. The phytic acid content of the wheat bran was effectively reduced by all treatments, and the phytic acid lost was in the range of 88.4–96.9%. Without addition of yeast or malt flour, or autoclaving without pH adjustment, the phytic acid content of the bran samples was reduced at most to 44.9% of the initial amounts under the investigated conditions. Increasing the concentration of yeast or malt flour or decreasing the pH towards 3.5 did not enhance the phytic acid reduction. The most reduction occurred after 2 h of yeast fermentation and malt flour incubation, and after 30 min of autoclaving, which made up 92–98% of the total phytic acid loss. Extending the treatment periods contributed nominally to further increase in the phytic acid reduction, and the rate of the phytic acid loss decreased progressively.     

In vitro pullulanase activity of wheat (Triticum aestivum L.) limit-dextrinase type starch debranching enzyme is modulated by redox conditions

Expression of a limit-dextrinase (LD) type starch debranching enzyme (EC 3.2.1.41) was observed in developing wheat (Triticum aestivum L.) endosperm and germinating grains, indicating a role for the enzyme in both biosynthesis and degradation of starch. A full-length cDNA, TaLD1, encoding LD in wheat developing kernels was isolated and predicted to encode a 98.6 kDa mature protein active in amyloplasts. Isolated cDNA was expressed in Escherichia coli to produce a recombinant His-tagged LD, which mainly accumulated in inclusion bodies as an inactive enzyme. Extraction of His-tagged LD from the inclusion bodies followed by dialysis under thiol/disulphide redox conditions allowed partial refolding of the protein and detection of pullulanase specific activities by zymogram analysis and enzyme assays. Several active conformations were demonstrated by the recombinant TaLD1 and pullulanase activity could be modulated by redox conditions in vitro. The results suggest that cellular redox conditions may regulate the level of LD activity in wheat tissues.     

Rheological properties and baking quality of wheat varieties from various geographical regions

Eight wheat varieties, originating from various geographical regions were examined for their rheological properties during large uniaxial and biaxial extensions and for their baking quality. Extensibility during uniaxial extension as well as biaxial extensional viscosity proved to be significant properties in predicting loaf volume. Multiple regression analysis indicated uniaxial extensibility and biaxial extensional viscosity as best predictors for loaf volume. The varieties with the highest strain hardening index were those of high loaf volume and also fine and soft crumb, whereas varieties of low strain hardening index were of poor baking quality. However, baking behaviour was not completely explained by considering only the strain hardening index. Crumb fineness was also investigated and it was taken into consideration when evaluating the varieties for their baking quality. 3D scatter plots of loaf volume, cell volume, and number of cells in the slice, divided the wheat samples in groups depending on their baking quality and common rheological characteristics were observed for these groups. The samples were also examined for their proofing capacity. Maximum dough height from the rheofermentometer correlated with loaf volume and was affected by rheological properties of the samples.     

Genetic variation of bioavailable iron and zinc in grain of a maize population

More than one-third of the world's population is afflicted by iron (Fe) and zinc (Zn) deficiencies, since cereal grain as a staple food of the people contains low levels or low bioavailability of Fe and Zn because of phytate. In maize, 80% of grain phosphorus (P) is in the form of phytate, and P could be an indicator of phytate content. The objectives of this study were (1) to estimate genetic variation of Fe and Zn in a maize population including P/Fe and P/Zn molar ratios as quantitative traits; (2) to determine relations among yield, P, Fe, Zn, P/Fe and P/Zn molar ratios; and (3) to define the implications of those on biofortification (breeding) programmes. There were significant genetic variations and workable heritabilities for Fe, Zn, P/Fe and P/Zn estimated in 294 F4 lines of a maize population, but there were no associations among six traits according to both simple correlations and principal component analysis. Weak correlations between P and Fe and between P and Zn indicated feasibility of breeding non low-phytic acid maize genotypes with more appropriate phytate/Fe and phytate/Zn relations. Bioavailability of iron and zinc varied substantially in a maize population justifying utilisation of these unique parameters in biofortification programmes.     

Environmental and genotypic influences on trace element and mineral concentrations in whole meal flour of einkorn (Triticum monococcum L. subsp. monococcum)

Trace elements (Zn, Fe, Cu and Mn) and minerals (Ca, Mg, P and K) concentrations were determined in whole meal flour of five einkorn accessions and one bread wheat cultivar, cropped in four different locations for two years. The major factors influencing mineral levels were year and genotype, as well as their interaction. Einkorn varieties exhibited higher Zn (7.18 ± 0.76 mg/100 g DM), Fe (5.23 ± 0.47), Mn (4.65 ± 0.23), Cu (0.90 ± 0.08), Mg (151.2 ± 9.00) and P (541.1 ± 35.37) concentration than bread wheat. Mg concentration correlated positively with that of other bivalent cations (Zn and Ca). The relevant amount of trace elements consistently found in einkorn further confirms the potential of this cereal in human nutrition, either by direct consumption or by introgression of superior alleles into enhanced polyploid wheat cultivars.     

Molecular characterization of the Puroindoline a-D1b allele and development of an STS marker in wheat (Triticum aestivum L.)

Kernel hardness is mainly controlled by one major genetic locus on the short arm of chromosome 5D in bread wheat. Twelve Chinese and CIMMYT wheat cultivars were characterized for the deletion region of Pina-D1b genotype and developing a novel STS marker for this allele. PCR and SDS-PAGE were used to confirm the Pina-D1b genotype, and then 20 pairs of primers were designed to amplify the fragment including deletion region in Pina-D1b genotype by primer walking strategy. An STS marker Pina-N spanning deletion region in Pina-D1b was developed and sequencing results showed that all of 10 Pina-D1b genotypes uniformly possessed a 15,380 bp deletion in comparison with that of Chinese Spring with wild type. This study provided an alternative method to exam Pina-D1b by molecular marker and will accelerate identification of puroindoline alleles in bread wheat.     

In vitro starch digestibility and predicted glycaemic indexes of buckwheat,oat, quinoa,sorghum, teff and commercial gluten-free bread

The in vitro starch digestibility of five gluten-free breads (from buckwheat, oat, quinoa, sorghum or teff flour) was analysed using a multi-enzyme dialysis system. Hydrolysis indexes (HI) and predicted glycaemic indexes (pGI) were calculated from the area under the curve (AUC; g RSR/100g TAC*min) of reducing sugars released (RSR), and related to that of white wheat bread. Total available carbohydrates (TAC; mg/4 g bread “as eaten”) were highest in sorghum (1634 mg) and oat bread (1384 mg). The AUC was highest for quinoa (3260 g RSR), followed by buckwheat (2377 g RSR) and teff bread (2026 g RSR). Quinoa bread showed highest predicted GI (95). GIs of buckwheat (GI 80), teff (74), sorghum (72) and oat (71) breads were significantly lower. Significantly higher gelatinization temperatures in teff (71 °C) and sorghum flour (69 °C) as determined by differential scanning calorimetry (DSC) correlated with lower pGIs (74 and 72). Larger granule diameters in oat (3–10 μm) and sorghum (6–18 μm) in comparison to quinoa (1.3 μm) and buckwheat flour (3–7 μm) as assessed with scanning electron microscopy resulted in lower specific surface area of starch granules. The data is in agreement with predictions that smaller starch granules result in a higher GI.     

宁夏小麦新品种特性及其与宁春4号的比较分析

本文对5份宁夏小麦新品种的产量稳定性、气象条件适应性、品质性状,结合当地的气象资料与宁春4号进行对比分析.结果表明,宁春39号、宁春38号为高产稳定品种;宁春40号、宁春37号为高产小稳定品种;宁春35号为低产不稳定品种.认定宁春39号、宁春38号为优势品种、宁春40号,宁春37号品种一般,适宜推广,宁春35号为劣势品种,不适宜推广.     

Molecular genetic approaches to increasing mineral availability and vitamin content of cereals

The present paper summarizes the current state of knowledge on molecular genetic approaches to increasing iron and zinc availability and vitamin content in cereals. We have also attempted to integrate the scientific issues into the wider context of human nutrition. In the cereal grain, iron and zinc are preferentially stored together with phytate in membrane-enclosed globoids in the protein storage vacuole (PSV) found in the aleurone and the embryo scutellum. The PSV is accordingly central for understanding mineral deposition during grain filling and mobilization of minerals during germination. Recent studies in Arabidopsis have led to the first identification of iron and zinc transporters of the PSV and further illustrate some of the dynamics associated with mineral and phytate transport and deposition into the vacuole. This provides new opportunities for modulating iron and zinc deposition in the cereal grain. Current strategies towards increasing the iron content of the endosperm are largely based on the expression of legume ferritin genes in an endosperm-specific manner. However, it is apparent that this approach, at least in rice, only allows a two- to three-fold increase in the iron content of the grain due to exhaustion of the iron stores in leaves. Further increases thus have to rely on additional uptake and transport of iron from the root. Phytate is generally considered to be the single most important anti-nutritional factor for iron and zinc availability. In the current paper we summarize attempts to increase phytase activity in the grain by transformation and evaluate the potential of this approach as well as the reduction of phytate biosynthesis for improving the bioavailability of iron and zinc. Vitamins constitute the second important group of micronutrients in grain and we discuss current efforts to increase the amounts of provitamin A, vitamin C and vitamin E.     

Association analysis of Puroindoline-D1 and Puroindoline b-2 loci with 13 quality traits in European winter wheat (Triticum aestivum L.)

Grain hardness, a major determinant influencing end-use quality of common wheat, is mainly controlled by Puroindoline a-D1 (Pina-D1) and Puroindoline b-D1 (Pinb-D1) genes. Recently, additional puroindoline genes, designated Puroindoline b-2 (Pinb-2), were described. This study examined frequencies of Pin-D1 alleles and Pinb-2 variants in 94 West European wheat genotypes and assessed their association with 13 quality traits considering population and family structure. The survey was completed by analyzing the Grain softness protein-1 gene. Results indicated sequence variation only for Pinb-D1 and Pinb-B2 genes. Pinb-D1b was the predominant hard allele. Pinb-B2v3-1 was the most common Pinb-2 variant, followed by a newly discovered variant Pinb-B2v3-5. Association mapping carried out in the whole sample population showed that Pinb-D1 alleles were associated with 11 quality traits, whereas Pinb-B2 variants were only associated with semolina extraction. Considering only the panel of hard wheat genotypes, variation for flour ash content, sedimentation value, gluten index and loaf volume was found to be associated with Pinb-D1 mutations suggesting that different Pinb-D1 mutations might have particular effects on quality traits. Our study indicated that Pinb-D1d was associated with inferior sedimentation value, gluten index and loaf volume, for which reason this mutation should be disregarded in breeding for quality wheat.