Distribution and composition of phytosterols and steryl ferulates in wheat grain and bran fractions

Phytosterols and steryl ferulates are bioactive compounds accumulating in the bran and germ of wheat. However, little is known regarding their localisation and composition in the bran layers of the kernel. The aim of this study was to determine the distribution of phytosterols and steryl ferulates in the wheat grain and in the different layers of bran. The wheat fractions, produced by conventional debranning, aleurone separation and a novel electrostatic process, were analysed for phytosterol contents using GC–FID and for steryl ferulate contents using HPLC–UV. The compounds were identified by GC– and LC–MS. Phytosterols and steryl ferulates were concentrated in the bran layers. The steryl ferulates were accumulated in the intermediate layers, whereas the phytosterols were more evenly distributed in the intermediate layers and aleurone cell contents. The phytosterol composition varied within the wheat kernel, while the steryl ferulate composition was similar in different fractions. Sitosterol and campestanyl ferulate were the main compounds. The highest levels of phytosterols (up to 2117 μg/g) and steryl ferulates (up to 703 μg/g) were found in the pearling, aleurone and certain bran fractions. The phytosterol-rich fractions could be utilised in cereal foods to enhance the intake of health-promoting compounds from natural sources.     

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.     

Analysis of free phytosterols/stanols and their intact fatty acid and phenolic acid esters in various corn cultivars

The contents and the compositions of free sterols/stanols, steryl/stanyl fatty acid esters and steryl/stanyl phenolic acid esters were determined in 25 corn cultivars grown at the same location and in the same year. The lipid extracts obtained from the flours of whole kernels were subjected to solid-phase extraction for the isolation and separation of the sterol classes, followed by capillary gas chromatography. The study provides for the first time information on the variability of individual steryl/stanyl fatty acid esters in corn cultivars. The analysis revealed pronounced differences in total contents of each sterol class. The levels of free sterols/stanols ranged from 298 to 433 μg/g dry matter flour, those of steryl/stanyl fatty acid esters from 430 to 1187 μg/g and those of steryl/stanyl phenolic acid esters from 46 to 240 μg/g. Free sterols/stanols were mainly composed of sitosterol and campesterol; up to 11% were made up of stanols. Steryl/stanyl esters of C18-fatty acids were dominating, with sitosteryl linoleate as the most abundant ester (44.7–53.5% of total fatty acid esters). Among the three investigated sterol classes, the distribution patterns of steryl/stanyl phenolic acid esters showed the greatest variability between the cultivars, even though trans-sitostanyl ferulate was the dominating ester in all samples.     

Pseudocereals as alternative sources for high folate content in staple foods

Total folate content was determined in the pseudocereals amaranth (four varieties), quinoa and buckwheat in comparison to four cereal species (eight wheat varieties, four barley varieties, one oat variety, one rye variety). Amaranth and quinoa were found to possess very high total folate contents: in amaranth, total folate ranged from 52.8 to 73.0 and in quinoa it was 132.7 μg/100 g dm, about ten times as much as in wheat. The bran fractions contained on average 124% of total folate, while only 57% on average was present in the flour fractions.     

Milling efficiency of triticale grain for commercial flour production

Triticale is a high yielding cereal grain, however low milling yields have discouraged its utilisation as a wheat alternative in processed flour products. This research investigated the role of hardness, grain size and tempering moisture on milling yields in modern triticale genotypes which do not exhibit shrivelled grain morphology. Replicate samples of three triticale varieties grown in two environments with a bread wheat standard were milled at five moisture contents. Both milling yield and ash content increased with decreasing tempering moisture in all genotypes. Triticale milling yield was between 7.1% and 10.1% less than wheat when tempered between 11% and 15% moisture respectively. The very hard textured triticale exhibited extremely low milling yield, similar to durum wheat. The ratio of ash in flour compared to bran was greater in triticale and the ash content of triticale flour could not be reduced to the level of wheat by alteration of tempering moisture. Surface area of larger triticale grain may also influence ideal tempering moisture, however further investigation is required. Milling yields and flour protein content in triticale can be improved by tempering triticale to lower moisture content, provided high ash content is not considered unfavourable in the final product.     

The antioxidant potential of milling fractions from breadwheat and durum

The effect of primary processing, namely milling, on the phenolic content and antioxidant capacity of two wheat cultivars, namely Canada Western Amber Durum (Triticum turgidum L. var. durum) and Canada Western Red Spring (Triticum aestivum L.) was studied. The milling products: bran, flour, shorts and feed flour fractions were examined. In addition, semolina was an end-product of durum wheat milling. Antioxidant activity of wheat phenoliocs was evaluated using oxygen radical absorbance capacity, inhibition of photochemiluminescence, the Rancimat method, and inhibition of oxidation of low-density lipoprotein cholesterol and deoxyribonucleic acid. The phenolic composition of wheat extracts was determined using high performance liquid chromatography. Bran showed the highest antioxidant activity whereas the endosperm possessed the lowest in both cultivars examined. The phenolic compounds are concentrated in the outermost layers namely the bran. The consumption of wheat with bran in the form of whole grain may provide beneficial health effects.     

Deoxynivalenol in wheat milling fractions: A critical evaluation regarding ongoing and new legislation limits

New maximum limits (ML) for deoxynivalenol (DON) in wheat and its products were set in Brazil in 2017, and new changes are scheduled for 2019. The concentration of DON in wheat and milling fractions (bran, shorts, break flour, reduction flour) was evaluated in samples from commercial fields to discuss the effects of the new legislation. Cleaned wheat samples contaminated with DON had concentrations ranging from 308 to 2373 ng g⁻¹ (n = 29), and one sample had a concentration of 3426 ng g⁻¹. DON concentration obtained in bran and shorts were significantly higher than that of the flours. Compared to the initial concentration in cleaned wheat, DON relative concentrations were 73 and 35% higher in bran and shorts, respectively, and 67% lower in the straight run flour (break plus reduction flour). The bran and straight run flour contained DON concentrations that were 62.1 and 17.2% respectively higher than that of the ML set in Brazil in 2017; additionally, these values would reach 65.5 and 34.5%, respectively, according to the changes to be in effect in 2019. The present study demonstrates DON distribution in wheat milling fractions, thus, providing updated information for the management of DON contamination for the industry and policymakers.     

不同基因型小麦籽粒、面粉和麸皮中Ca和Zn含量的差异

为了筛选富含人体必需营养元素钙（Ca）和锌（Zn）的小麦品种,改善食品营养结构,以来自长江中下游地区的推广品种和部分国内外引进的小麦品种（共112个）为材料,进行了籽粒Ca和Zn含量的测定和分析,通过聚类分析选出其中39个代表性品种,对其麸皮和面粉中的Ca和Zn含量进行了进一步分析。结果表明,不同基因型品种籽粒中Ca和Zn含量的变异范围较宽,品种间存在极显著差异,面粉、麸皮和籽粒中均存在含量较高的品种。Ca和Zn含量均表现为麸皮中最高,变异幅度最宽,籽粒中次之,面粉中最低且变异幅度也较小,但“面粉麸皮籽粒”中营养元素的含量关系比较复杂,并不总是呈显著正相关。品种NP164、青紫1号和荆州D402等可作为提高当地小麦面粉Ca和Zn含量的重要种质资源加以应用。     

Biochemical markers: Efficient tools for the assessment of wheat grain tissue proportions in milling fractions

To produce safe and healthy whole wheat food products, various grain or bran dry fractionation processes have been developed recently. In order to control the quality of the products and to adapt these processes, it is important to be able to monitor the grain tissue proportions in the different milling fractions produced. Accordingly, a quantitative method based on biochemical markers has been developed for the assessment of grain tissue proportions in grain fractions. Grain tissues that were quantified were the outer pericarp, an intermediate layer (including the outer pericarp, the testa and the hyaline layer), the aleurone cell walls, the aleurone cell contents, the endosperm and the germ, for two grain cultivars (Tiger and Crousty). Grain tissues were dissected by hand and analysed. Biochemical markers chosen were ferulic acid trimer, alkylresorcinols, para-coumaric acid, phytic acid, starch and wheat germ agglutinin, for outer pericarp, intermediate layer, aleurone cell walls, aleurone cell contents, endosperm and germ respectively. The results of tissue quantification by hand dissection and by calculation were compared and the sensitivity of the method was regarded as good (mean relative errors of 4% and 8% for Crousty and Tiger outer layers respectively). The impact of the analytical variability (maximum 13% relative error on coarse bran) was also regarded as acceptable. Wheat germ agglutinin seems to be a promising marker of wheat germ: even if the quantification method was not able to quantify the germ proportions in milling fractions, it was able to classify these fractions according to their germ content. The efficiency of this method was tested, by assessing the grain tissue proportions of fractions exhibiting very different compositions such as flour, bran and aleurone-rich fractions obtained from three different grain or bran dry fractionation processes (conventional milling, debranning process, production of aleurone-rich fractions from coarse bran). By calculation of the composition of the different products generated, it was possible to study the distribution of the different tissues among fractions resulting from the different fractionation processes. This quantitative method is thus a useful tool for the monitoring and improvement of processes, and allows the effects of these processes to be understood and their adaption to reach the objectives.     

The effect of particle size of wheat bran fractions on bread quality – Evidence for fibre–protein interactions

The nature of the adverse effects of wheat bran fractions on bread-making quality was studied. Two fractions of bran, representing different tissue layers and having different compositions, were used. The particle size of the bran fractions was varied by various milling techniques. All fractions were added to white flour and water addition was adjusted to obtain dough with a constant consistency.     

Sulphur nutrition differentially affects the distribution of asparagine in wheat grain

Asparagine is known to accumulate in wheat grain under conditions of sulphur deficiency, leading to increased levels of acrylamide formation during processing. Analyses of milling fractions and of the outer layers of the grain prepared by hand dissection showed that the highest levels of asparagine were present in the bran fractions and in particular the aleurone layer, when grain were grown with sufficient sulphur supply. However, even mild S deficiency resulted in disproportional increases in the asparagine contents of white flour fractions, implying that optimisation of yield in a conventional milling system is not an appropriate strategy for processing grain from sulphur-deficient crops.     

Milling,functional and thermo-mechanical properties of wheat,rye, triticale,barley and oat

The milling potential of hulled barley, hulled oat, triticale, rye and wheat was studied using a long tempering process and a laboratory four-roller mill. Regardless of the investigated cereal, the results indicated a significant influence (p < 0.05) of volume per surface area ratio on the milling yield and ash contents of the flour. The lowest milling yield was obtained in case of hulled oat. Solvent retention capacity profiles were determined for all investigated whole cereals and flours for predicting the contribution of different polymers to the functionality of samples. For all solvents higher values were obtained for the whole cereals compared to the corresponding flour. Thermo-mechanical properties of the whole cereals and refined flours were also investigated. If in case of wheat the gluten proteins play an essential role on dough behaviour during kneading at 30 °C, in case of triticale, rye, hulled barley and hulled oat, the fibers play a major role as well. Thermo-mechanical properties of starch registered a large variation between cereals and/or flours. The lowest torque value corresponding to starch gelatinization (C3) was registered in case of the hulled oat flour, 1.92 Nm, while the highest value in case of rye flour, 2.65 Nm.     

Changes in common wheat grain milling behavior and tissue mechanical properties following ozone treatment

Ozone treatment (10 g/kg) of common wheat grains with a new patented process, Oxygreen^®, used before milling was found to significantly reduce (by 10–20%) the required energy at breaking stage whatever the grain hardness and without changes in the flour yield. Detailed study of each of the milling steps undertaken on a hard type cultivar showed that both the breaking and the reduction energy were decreased. Reduction of the coarse bran yield was also observed concomitantly with an increase in the yield of white shorts. Biochemical characterization of the milling fractions pointed out changes in technological flour properties as starch damage reduction, aleurone content enrichment and increase of insoluble glutenin polymers. Measurement of wheat grain tissue mechanical properties showed that ozone treatment leads to reduction of the aleurone layer extensibility and affects the local endosperm resistance to rupture. These data as well as the direct effect of ozone oxidation on biochemical compounds could explain the observed changes in milling energy, bran and shorts yield and flour composition.     

Influence of long-term nitrogen fertilization on micronutrient density in grain of winter wheat (Triticum aestivum L.)

A long-term (1999–2007) field experiment was conducted to investigate the effects of three nitrogen (N) fertilization rates (0, 130, and 300 kg N/ha) on micronutrient density in wheat grain and its milling fractions. At maturity, grains were harvested and fractionated into flour, shorts, and bran for micronutrient and N analysis. N fertilization increased iron (Fe), zinc (Zn), and copper (Cu) density in wheat grain compared to the control. Increase of N application rate from 130 to 300 kg N/ha, however, did not further increase the three micronutrient densities in grain. Micronutrient concentrations were usually highest in the bran and lowest in the flour. High N application increased Zn and Cu densities in all three milling fractions and increased Fe concentration in shorts and bran but not in flour. N application did not affect the manganese (Mn) concentration in grain. N fertilization changed the proportions of Fe and Cu in flour and bran but did not affect the distribution of Zn. Because N fertilization increased micronutrient accumulation in wheat grain, proper management of N fertilization has the potential to enhance the nutritional quality of this important food.     

Antioxidant properties of wheat and rye bran extracts obtained by pressurized liquid extraction with different solvents

Rye and wheat brans are valuable sources of bioactive compounds, which could be used for the development and commercialization of high added value functional ingredients such as dietary antioxidants. The aim of this study was to evaluate antioxidant potential of rye and wheat bran using different polarity solvents. Cereal brans were ground to four different particle size fractions and extracted at 10.3 MPa pressure and 80 °C temperature by consecutive application of hexane, acetone and methanol:water (80:20%). The highest extract yield was obtained from rye bran using methanol-water; particle size in most cases had a significant effect. Antioxidant potential of extracts was assessed by ABTS^+•, DPPH^• scavenging, ORAC and total phenols content (TPC) assays. Extraction solvent had a major influence on TPC and antioxidant activity of the extracts. The most active extracts were obtained using methanol:water; rye bran extracts, in general, were stronger antioxidants than wheat bran extracts. For the majority of assays, reduction of particle size resulted in higher antioxidant activity values. However, ABTS^+• scavenging was found to decrease by decreasing particle size of rye bran used for extraction.     

Fatty acids profile,sterols, tocopherol and squalene content in Fagopyrum tataricum seed milling fractions

There is no data on the lipid profile of Fagopyrum tataricum grain and its milling products. Therefore, we aimed to assess the phytosterol and tocopherol content and fatty acid profile of the samples of F. tataricum. Grain was milled, then the milling product separated to hull, bran, and two flour fractions, differing in particle size. The highest level of lipids (total fatty acids – 83%, with dominant oleic acid – 40%) was observed in the bran fraction (380 μm > GA > 180 μm). All samples contained some natural cis fatty acids, such as vaccenic acid (C18:1 n-7; ~2.8%) and tocopherol (α-, β-, δ- and γ-tocopherol). The highest content of total tocopherol was also detected in the bran fraction (0.1% of lipids). The content of lipid soluble bioactive substances was different and depended on the size of obtained fraction, therefore properly designed grain processing technology can be used to produce food with high nutritional value.     

Distribution of bioactive compounds in maize fractions obtained in two different types of large scale milling processes

Maize kernels contain different bioactive compounds that are important for human health. The aim of this study was to analyze the distribution of the bioactive compounds in maize fractions derived from two industrial dry-milling processes, characterized by a dry-degermination (DD) system and a tempering-degermination (TD) system.The bioactive compounds in maize resulted unevenly distributed in the milling fractions of the kernel. By-products such as the germ and the animal feed flour, had higher total antioxidant capacity (TAC), total polyphenol content (TPC) and total dietary fibre content (TDF) than the whole grains, while xanthophyll and resistant starch resulted to be higher in the fractions derived from the vitreous endosperm. The germ fraction showed also the highest folate content. Results also showed that the type of degermination process influences the bioactive compound contents in the milling fraction, in accordance to the effectiveness of the germ and bran removal from the endosperm fractions. In particular, the animal feed flour obtained by means of TD system resulted in a higher TAC, TPC and TDF than the same fraction obtained by means of the DD system. Conversely, the extraction rate do not affect the recovery of bioactive components in particular fractions.     

Antioxidant properties of wheat mill streams

Knowing the quality of mill streams is very important for getting flours with improved quality. In the present work, 49 mill streams, obtained by milling common wheat with an industrial roller mill, were characterized in terms of phenolic content, antioxidant activity and iron content. The antioxidant activity was estimated using different methods: DPPH-radical scavenging, Trolox equivalent antioxidant capacity, and iron reducing antioxidant power. The break tailings and first tailings of the reduction passages had the largest contents of iron. The total phenolic contents (TPC) from flour streams ranged between 76.3 and 369 mg ferulic acid equivalent/100 g d.w. The highest TPC were obtained for the second fractions resulting from 1st and 2nd break rolls. The highest antioxidant activity was registered for flour streams collected from: the last two break rolls, the reduction rolls that process the tailings of the first three reduction passages and bran finisher. Trolox equivalent antioxidant capacity had the same trend as DPPH-radical scavenging activity. The highest iron reducing antioxidant power was found in the tailings of the reduction rolls. The knowledge provided by this study could be successfully applied for getting flour with improved antioxidant activity and iron content by mixing different types of mill streams.     

Lignans in triticale grain and triticale products

This study determined the lignan content of seven varieties of triticale grain and compared these values with wheat and rye grain, with triticale milling fractions (bran, shorts, and refined flour), and triticale products (sprouted grain, malt, fermented bread dough, baked dough, dried pasta and cooked pasta). Acid hydrolysis and enzymatic hydrolysis were used to release the lignans in extracts. We carried out qualitative and quantitative analysis of secoisolariciresinol, matairesinol, lariciresinol, syringaresinol, and pinoresinol levels using an Acquity UPLC liquid chromatograph with photodiode and mass Acquity TQD detectors. The most abundant lignan in all samples was syringaresinol, which made up 80% of all lignans. The lignan content of triticale grain varied from 392 to 792 μg·100gd·m⁻¹ (acid hydrolysis) and from 685 to 1189 μg·100gd·m⁻¹(enzymatic hydrolysis), depending on the variety. The lignan levels in triticale bran were almost three times those found in the grain; in flour, there was one fifth or even one tenth as much, whereas the shorts had similar levels as the grain. After three days of germination, the amount of lignans in the triticale grain increased by 17%–32%. A greater increase in lignan content (by factors of 1.4 and 2.3) was found in triticale after extrusion cooking. Fermentation led to lignan concentrations increasing slightly (2–14%), but this was then reduced in the baking process. Extracts from dry pasta contained similar or lower amounts than did the raw material, but the concentration was higher in cooked pasta (14%–47%). The enzymatic hydrolyzed extracts contained on average 36% higher lignan content than did the acid hydrolyzed samples.     

Low moisture milling of wheat for quality testing of wholegrain flour

The objective of this study was to produce wholegrain wheat flour on a laboratory-scale with particle size distributions similar to commercially-milled samples without re-milling the bran. The moisture contents of four hard winter wheat cultivars were adjusted to 7.29–7.98% (by drying), 9.00–10.6% (“as is”), and 15.6% (by tempering) prior to milling into wholegrain flour. The moisture treatments appeared to affect the partitioning of wholegrain flour particles into each of three categories: fine (<600 μm), medium (600–849 μm) and coarse (≥850 μm). When the distributions of particles were grouped into these categories, wholegrain flours made from dried and “as is” wheat fell within the values for commercial wholegrain flours, while that from tempered wheat contained more coarse particles than even the coarsest commercial wholegrain flour. Loaf volumes and crumb firmness were not significantly different between bread made from wholegrain flour that had been produced from dried or “as is” wheat, but loaf volume was significantly lower and bread crumb firmness was significantly higher when wholegrain flour from tempered wheat was used. These results show that wheat may be milled without tempering to produce wholegrain flour with particle size similar to some commercially-milled flours without needing to re-grind the bran.