Phytase activity, phytate, iron, and zinc contents in wheat pearling fractions and their variation across production locations

Pearling is an effective method for evaluating the distribution of chemical components in wheat grain. Twelve pearling fractions (P₁–P₁₂) of wheat grain were obtained using two rice polishers for 10 cultivars (six soft red wheats and four hard white wheats) grown at two locations with different environmental conditions in Jiangsu Province, China. The results show that the effects of cultivar, location, and pearling on wheat flour phytase activity, phytate, iron, and zinc contents were all significant, with pearling having the greatest effect. All the four components showed a diminishing trend as pearling progressed from the outer layers to the inner part of wheat grain. Generally, the P₂ fraction (the outer 4–8% layer of wheat grain) had the highest phytase activity and phytate and iron contents, whereas the P₁ fraction (the outer 0–4% layer) ranked the highest for zinc content. Growing location had a large influence on grain phytase, phytate, and iron, but the differences between locations decreased as pearling level increased.     

<Emphasis Type="Italic">Pulque</Emphasis>, An Alcoholic Drink from Rural Mexico,Contains Phytase. Its <Emphasis Type="Italic">in vitro</Emphasis> Effects on Corn Tortilla

Pulque is made by fermenting the agave sap or aguamiel of Agave atrovirens with a whole array of microorganisms present in the environment including several lactic acid bacteria and yeasts such as Saccharomyces cerevisiae. Ascorbic acid was determined in pulque and aguamiel, respectively. Phytase activity in lees, liquid and freeze-dried pulque was assayed by measuring the appearance of phosphate from phytate by a colorimetric method likewise phosphate from phytate present in fresh corn tortilla was measured after in vitro incubation with pulque. Iron, zinc, calcium, magnesium and selenium contents were measured in pulque and corn tortilla as well as in nixtamalized corn flour (NCF), the latter is used to make instant tortilla, since corn provides most of the energy as well as most of the phytate in the Mexican rural diet. Pulque showed phytase activity but much less ascorbic acid and iron than previously reported; additionally, phytase in pulque hydrolyzed most of phytate’s corn tortilla. Lees, which is mostly made of pulque’s microbiota, significantly accumulated iron and zinc but no selenium. NCF was fortified with iron by the manufacturers but poorly blended. There were significant differences on selenium content between tortillas samples, apparently some soils in central Mexico are selenium deficient. Moderate pulque intake appears to increase the bioavailability of iron and zinc bound by phytate in corn.     

玉米铁微营养生物有效性与生物强化的研究进展

综述了玉米子粒中铁的分析方法、生物有效性及其影响因素、铁生物强化的传统与分子育种途径的研究进展,并对HarvestPlus项目与组织作了概略的介绍。     

黄淮海区主推玉米品种子粒主要矿物质元素含量分析

对黄淮海区36个主推玉米品种子粒各微量和常量矿物质元素含量进行分析。结果表明,玉米子粒Zn、Fe、Mn和Cu浓度变化范围分别为16.2~24.0、17.7~32.9、3.3~7.4和1.1~2.4 mg/kg,其平均浓度分别为20.1、23.0、4.5和1.6 mg/kg,变异系数分别为10.3%、23.0%、23.9%和22.1%。Ca和Mg浓度范围分别为37.8~93.5和1 002.1~1 357.4 mg/kg,平均浓度分别为68.3和1 163.2 mg/kg,变异系数为25.3%和7.9%。N,K和P浓度范围分别为8.9~14.0、3.2~4.8和2.2~3.0 g/kg,平均浓度分别为11.5,3.9和2.6 g/kg,变异系数分别为12.4%,10.7%和8.3%。子粒中60.2%~85.9%的P以植酸磷形态存在,与Zn和Fe均无相关性;Zn和Fe同时与Mn、Mg和K呈显著正相关,表明玉米子粒中Zn、Fe、Mn、Mg和K浓度提高的同时不会提高植酸P浓度,有利于提高子粒Zn和Fe的生物有效性。     

Changes in micro- and macronutrient composition of pearl millet and white sorghum during in field versus laboratory decortication

Traditional decortication of pearl millet and white sorghum by hand pounding or using a mechanical device were performed in Burkina Faso, and compared to abrasive decortication in the laboratory using the same kernel lots. Using some nutrients as histological markers, the decortication characteristics and nutritional composition (iron, zinc, phytates, lipids, ADF fibres and starch) of decorticated grains were measured. Decortication had numerous effects on grain composition but no significant differences were observed between the two traditional methods of decortication. The effects varied according to the type of grain mainly due to the fact that more germ was removed in sorghum than in millet, as the millet germ is more embedded in the endosperm. During abrasive decortication, zinc and lipid losses increased rapidly due to removal of the germ, particularly in sorghum. Phytates were shown to be located mainly in the bran and germ but also in the endosperm in millet. In both sorghum and millet, half the iron was removed when only 10% of grain DM was abraded. The method of decortication, shock or friction vs. abrasion, influenced the fractions removed and thus the chemical composition of the decorticated kernels.     

花粉直感对普通玉米子粒淀粉含量的影响

以9个淀粉含量不同的玉米自交系为亲本,按照Griffing I双列杂交模式组配72个当代杂交组合,测定子粒淀粉含量,分析花粉直感现象对玉米子粒淀粉含量的影响。结果表明：当同一母本授以不同父本花粉时,当代组合淀粉含量存在明显差异;花粉直感现象对当代子粒的淀粉含量存在正负双向影响,其最大增幅为6.59％,最小增幅-5.00％;高淀粉含量的亲本Lx00-6作父本,所得到当代组合子粒淀粉含量均高于母本。     

植酸酶对大豆中植酸降解作用的研究

以植酸钙作为唯一的磷源,从无花果中分离到一株产植酸酶的菌株,利用该菌株液体发酵所得到的粗酶处理脱脂大豆粉,３０℃下反应９０℃分钟,植酸（盐）降解率过７５％,处理液中可溶性蛋白质含量由０．１６７ｍｇ／ｍｌ增加到１２．１ｍｇ／ｍｌ。     

离子交换法制备低植酸含量大豆蛋白的研究

大豆食品中的植酸会阻碍多种矿物离子及蛋白的吸收,为了提高大豆蛋白的营养吸收性,加工中应去除植酸。本文研究了离子交换法脱除大豆分离蛋白中植酸的方法和效果,并进一步考察了处理后大豆蛋白的理化性质。结果表明:透析、超滤与离子交换法进行比较,阴离子交换后植酸含量下降77%,较优于其他方法。后采用离子交换法去除大豆蛋白中的植酸,对不同树脂、不同蛋白状态及酸碱度对植酸的去除效果进行比较,以确定植酸去除的最优方案。与其他树脂相比,D201树脂对植酸的吸附率达到12 mg·m L-1,在p H7.0的条件下可将植酸含量降低到1 mg·g-1,下降约90%。制备的低植酸含量的大豆蛋白等电点向右偏移,溶解性略有下降,分散速度有所提高。     

Localisation of iron in wheat grain using high resolution secondary ion mass spectrometry

Insufficient iron (Fe) is one of the most prevalent micronutrient deficiencies in humans, with billions of people affected. Cereal grains are an important source of Fe for humans but the bioavailability of Fe in cereals is generally low. Information regarding the cellular and sub-cellular localisation of Fe in wheat grain will aid optimising nutrient delivery for human health. In this study high resolution secondary ion mass spectrometry (NanoSIMS) was used to map the distribution of Fe in the aleurone layer and in the endosperm of immature wheat grain. Iron was shown to be localised strongly in the phytin globoids in the aleurone cells and to a lesser extent in the cytoplasm around the starch granules in the endosperm.     

The influence of fermentation processes and cereal grains in wholegrain bread on reducing phytate content

Wholegrain bread is generally thought of as being more healthy than white bread due to it having a higher content of dietary fibre, vitamins (especially vitamin B and E) and many important minerals. However, wholegrain bread also contains high levels of phytate (myo-inositolhexakisphosphate, InsP-6) which may bind desirable nutrients, preventing their absorption in the gut and thereby reducing the nutritional value of the end product. In order to evaluate factors influencing phytate levels, the effects of fermentation and selected wholemeal flours from rye, oats and wheat were investigated. Phytate levels were assessed using a spectrophotometric assay based on the measurement of iron with 2,2′-bipyridine. Phytate decreased in freshly ground wholegrain flour dough during the fermentation process with time of fermentation being the most important factor. Fermentation temperature was found to make only a small difference to the process of phytate reduction. Since the potential benefits of wholemeal breads incorporating various grains (e.g. oats and rye) are increasingly evident, this research has important implications for human health.     

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.     

正交实验法优化转基因玉米中植酸酶的提取工艺

采用正交实验法研究pH值、料液比和提取时间等因素对酶提取效率的影响,探索超声提取转基因玉米中植酸酶最佳提取条件。结果显示,最佳提取条件为提取液pH值5.5,料液比为1∶4,提取时为15 min。     

Phytate and mineral elements concentration in a collection of Italian durum wheat cultivars

Mineral deficiencies are prevalent in human populations and the improvement of the mineral content in cereal products represents a possible strategy to increase the human mineral intake. Nevertheless, most of the inorganic phosphorus (P_i) present in mature cereal seeds (40–80%) is stored as phytate, an anti-nutritional factor that forms complexes with minerals such as Ca, Mg, Zn and Fe reducing their bioavailability. The present study was undertaken: (i) to determine the variation in phytate and mineral concentrations in the whole grains of 84 Italian durum wheat (Triticum durum Desf.) cultivars representative of old and modern germplasm; (ii) to estimate the magnitude of genotype × environment interaction effects; and (iii) to examine the interrelationships among mineral concentrations in durum wheat with the final aim to identify superior durum wheat cultivars that possess low phytate content and high concentration of mineral elements in their whole-wheat flour. The cultivars were grown in field trials during 2004–2005 at Foggia, Italy and during 2005–2006 at Foggia and Fiorenzuola d’Arda—Southern and Northern Italy. The phytate content was estimated indirectly by using a microtitre plate assay evaluating the P_i absorbance at 820 nm, while the Cu, Fe, Mn, Ca, K, Mg, Na and Zn mineral contents were determined by ICP/OES. The contents of Zn and Fe across years and locations ranged from 28.5 to 46.3 mg/kg for Zn with an average of 37.4 mg/kg and from 33.6 to 65.6 mg/kg for Fe with an average of 49.6 mg/kg. P_i grain content was between 0.46 and 0.76 mg/g showing a positive correlation with all minerals except Cu and Zn. Although breeding activity for Fe and Zn would be difficult because G × E interaction is prevalent, multi-location evaluation of germplasm collection help to identify superior genotypes to achieve this objective. The results here reported open the possibility of designing a specific breeding program for improving the nutritional value of durum wheat through the identification of parental lines with low-P_i and high minerals concentration in whole grains.