Cell wall composition of 1B/1R translocation wheat grains

The cell wall composition and total dietary fibre content of 12 different winter wheat cultivars both without and with 1B/1R gene were analysed. Translocation wheat (with 1B/1R gene) had higher contents of extractable xylose and unextractable mannose residues than standard wheat (without 1B/1R gene). Three sieved flours of standard wheat, translocation wheat and rye respectively were used for further detailed studies. Water‐extractable arabinoxylan was isolated and fractionated on a DEAE‐cellulose column. The water‐eluted fraction of translocation wheat had a higher proportion of monosubstituted xylose residues than the same fraction of standard wheat, which is a typical feature of rye arabinoxylan. Molecular weight determination showed that rye water‐eluted arabinoxylans were larger than those of wheat. The molecular weight of translocation wheat arabinoxylan was lower than that of standard wheat and had a high polydispersity. Xylanase‐resistant arabinoxylan was extracted from all three flours, and NMR studies showed that wheat xylanase‐resistant arabinoxylan had a lower amount of monosubstituted xylose residues, while the rye fraction was rich in consecutive disubstituted xylose residues. Translocation wheat xylanase‐resistant arabinoxylan resembled that of standard wheat. © 2002 Society of Chemical Industry     

Effect of Peroxidase on Textural Quality of Dough and Arabinoxylan Characteristics Isolated from Whole Wheat Flour Dough

Effect of peroxidase on arabinoxylans (pentosans) isolated from whole wheat flour and instrumental textural parameters of whole wheat flour dough were studied. Significant increase in dough hardness and decrease in adhesiveness was observed on treatment of dough with peroxidase. Arabinoxylans isolated from peroxidase treated dough had higher molecular weight, viscosity, arabinose to xylose ratio, ferulic acid, and protein contents as compared to that of untreated dough. Arabinoxylans isolated from treated dough had higher absorption at 280 and 320 nm indicating the association of proteins and ferulic acid with arabinoxylans. Thus, the treatment of dough with peroxidase may catalyze the formation of cross-linking between arabinoxylans as well as protein-arabinoxylan that could be responsible for the alteration of the whole wheat flour dough characteristics.     

黑麦水溶性阿拉伯木聚糖制备及其在面包生产中应用

该文采用黑麦粉,经过加热提取,乙醇沉淀后得到的黑麦水溶性阿拉伯木聚糖,作为功能性食品添加剂应用于面包生产中,探讨黑麦阿拉伯水溶性木聚糖对面包品质的影响。结果表明:面粉中添加黑麦阿拉伯水溶性木聚糖能改善面粉品质,增加面包体积;另外,因其具有较高的持水性,可减缓淀粉老化,延长面包货架期,提高面包品质。     

Origin and practical significance of the sticky dough factor in 1BL/1RS wheats

When translocated into wheat, the short arm of the 1R chromosome of rye carries with it linked resistance genes to powdery mildew, stripe rust, leaf rust and stem rust. The translocation is also reported to increase yield potential of hard wheats. However, many doughs made from some 1BL/1RS hard wheats are unacceptable for breadmaking purposes because of excessive stickiness and mixing intolerance. 1BL/1RS wheats may be sticky because of: the inheritance of secalin proteins from rye and absence of key glutenin subunits; higher amounts and/or differences in the composition of cell wall polysaccharides, β‐glucans and pentosans; and/or the presence of a ferulic acid ester moiety residing with the water‐soluble fraction of 1BL/1RS flours. None of these hypotheses has been proven or disproven, to date, as a cause of excessive stickiness. Investigators have found that 1BL/1RS doughs are not uniformly sticky and are in some instances less sticky than non‐1BL/1RS doughs. Significant genotype–environment interactions have been reported for dough stickiness and flour quality characteristics of 1BL/1RS wheats. Investigators have generally failed to find significant differences in the breadmaking performance of 1BL/1RS and non‐1BL/1RS hard wheats despite a report that 1BL/1RS doughs break down and soften during high‐speed mixing. The 1BL/1RS translocation has been shown to reduce cookie spread of soft wheat flours but has no deleterious effects on cake volume or texture. © 2002 Society of Chemical Industry     

An explanation for the combined effect of xylanase–glucose oxidase in dough systems

In the bakery industry, glucose oxidase is usually used in combination with xylanase. Although many theories exist on the mechanism of action of each enzyme, the positive effect of combining the two is as yet unexplained. In this paper we studied a possible basis for this synergy by focusing on the involvement of arabinoxylans. Water‐extractable arabinoxylans and water‐unextractable solids were studied in dough with or without glucose oxidase. Addition of glucose oxidase led to a stiffer and less extensible dough. Addition of arabinoxylans caused a further decrease in dough extensibility. Addition of xylanase could correct for this decrease. The role of arabinoxylans was further investigated by studying modified water‐extractable arabinoxylans and the effect of agents affecting arabinoxylan crosslinking (ferulic acid). Water‐extractable arabinoxylan was modified with xylanase to generate a low‐molecular‐weight fraction (WEAX_XYL). Alternatively, it was modified with NaOH to prepare a fraction with a decreased ferulic acid content (WEAX_OH). Addition of modified arabinoxylans diminished the effect of glucose oxidase. Glutenin macropolymer and water‐extractable arabinoxylan viscosity experiments were performed to obtain further detail on the role of arabinoxylans (AX). These results give rise to a new theory explaining the contribution of xylanase in its synergy with glucose oxidase. In this theory glucose oxidase not only catalyses the formation of protein disulfide bonds, but also of AX‐AX crosslinks. The latter negatively affect bread quality. Xylanase corrects for this latter effect by cleaving arabinoxylan complexes and generating small ferulic acid‐containing arabinoxylan fragments interfering with the crosslinking of high‐molecular weight arabinoxylans. Copyright © 2005 Society of Chemical Industry     

The composition of a gel formed when wheat flour is suspended in phenol-acetic acid-water (1:1:1, w/v/v)

A gel which formed when wheat flour was suspended in phenol-acetic acid-water (1:1:1, w/v/v/) was fractionated into a protein-rich soluble fraction and a carbohydrate-rich insoluble fraction. Gel electrophoresis showed that the soluble fraction contained several proteins and had an amino acid composition with a high content of proline and glutamyl residues and a low content of lysine. The soluble fraction also contained lipids which were mainly phospholipids, phospholipid derivatives and glycolipids and other compounds, which yielded galactose and glucose after acid hydrolysis. The insoluble fraction contained a polysaccharide with similar properties to starch, and lipids which were mainly neutral fats, sterols and sterol esters. Both fractions contained arabinoxylans and mannans. The gel did not contain any nucleic acids. The protein-rich soluble fractions of gels prepared from other wheat flours and air-classified flour fractions, from wheat gluten and from rye and barley flours, showed marked differences in amino acid composition. It is concluded that a heterogeneous class of proteins, rather than specific proteins in fixed proportions, is involved in gel formation.     

Changes in dietary fibre, phenolic acids and activity of endogenous enzymes during rye bread-making

The content and composition of dietary fibre (DF), phenolic acids and ferulic acid dehydrodimers as well as the activity of endogenous enzymes were measured in freeze-dried samples of rye wholemeal, dough and bread during the rye bread-making process. Activities of !-amylase, #-xylosidase, !-arabinofuranosidase, and cinnamoyl esterase(s) were found in extracts of wholemeal and in dough after mixing and proofing, whereas activity of endo-xylanase was only found in the wholemeal. As a result of dough mixing, the content of total DF decreased by 21%, which was caused by a decrease in the amount of water-unextractable (WUE) DF. The content of water-extractable (WE) DF was unchanged during the bread-making process, but the relative content of WE DF increased. The content of total ester-bound phenolic acids and ferulic acid dehydrodimers decreased from 1575 µg/g in the wholemeal to 1472 µg/g in rye bread. The most pronounced effect occurred in an imitated sour dough (acidified with lactic and acetic acid instead of by lactic acid bacteria). The observed changes in content and solubility of DF in the dough could be explained by the activity of endogenous enzymes and mechanical disaggregation, whereas the changes observed in the imitated sour dough indicated that some acid hydrolysis might also have taken place.     

Effects of arabinoxylan solubilization on wort viscosity and filtration when mashing with grist containing wheat and wheat malt

Arabinoxylans are partially water-extractable, high-molecular-weight polymers that contribute to the problems of viscosity and membrane filterability during beer brewing. These problems are more pronounced when wheat and wheat malt are used as adjuncts due to their higher arabinoxylan contents and higher molecular weights. This paper aimed at investigating the effects of mashing temperature, time, grist size and liquor:grist ratio on the solubilization of arabinoxylans. Results indicated that increasing the mashing temperature generally increased the amount of arabinoxylans released into the wort. When greater proportions of wheat or wheat malt were used as adjunct, higher arabinoxylan contents in the final wort were observed. The more finely ground the grist, the more were arabinoxylans released into the wort. When more diluted mashes were used, more efficient solubilization of arabinoxylans was observed. The effects of arabinoxylan content and β-glucan content on the wort viscosity were also examined using a General Linear Model (GLM). There was a good correlation (R² = 0.98) between wort viscosity and its arabinoxylan and β-glucan contents.     

Macromolecular structure of water-extractable arabinoxylans in endosperm and wholemeal rye breads as factor controlling their extract viscosities

Viscosity is one of the most important attributes of rye-based products related to some health benefits. To identify the factors affecting arabinoxylan-dependent extract viscosity (AX-EV) of rye bread, the structural features of water-extractable arabinoxylans (WE-AXs) and their ammonium sulphate precipitated subfractions were investigated in breads with varied viscosities. Also, an endoxylanase activity in the starting flours was examined. The HPSEC-RI profiles revealed the higher extent of AX depolymerisation in whole-meal bread (WMB) when compared to that in endosperm bread (EB), resulting in its lower AX-EV. This was mostly related to lower molecular weight of the parent WE-AX fraction with distinctly lower proportion of 2-Xylp in the chain. The AX-EV of rye bread decreased with decreasing proportion of AX-I, the major subfraction with 3-Xylp as only branching site. The endoxylanase activity was at least two times lower in endosperm flour than that in WM and negatively correlated with the AX-EV of WMB. The importance of densely substituted AX subfractions with exclusively 2-Xylp and 2,3-Xylp branches, protecting the AX-I from enzymic degradation during bread-making, has been evidenced.     

Effects of Xylanase and Peroxidase on Soluble and Insoluble Arabinoxylans in Wheat Bread Dough

ABSTRACT: Bread doughs supplemented with xylanase and xylanase plus peroxidase were fractionated into 4 insoluble and 3 soluble fractions. Chemical analysis and high-performance size-exclusion chromatography analysis of apparent molecular weight distribution indicated that xylanase acts on both cold-water-extractable arabinoxylans and on those that can be solubilized from cell wall fragments by hot water extraction. Peroxidase action increased the amount of insoluble small cell wall fragments, notably the amount of protein and arabinoxylan. Arabinoxylans were retained in the small cell wall fragments because cross-linking of arabinoxylans through ferulic acid residues to other arabinoxylans rendered them insoluble. Peroxidase did not affect the composition of gluten, nor was evidence obtained for peroxidase-catalyzed cross-linking of arabinoxylans to protein in the gluten and other fractions.     

普通小麦阿拉伯糖基木聚糖含量快速测定及其遗传特性分析

阿拉伯糖基木聚糖是重要的小麦品质性状,对饼干和蛋糕等烘烤品质具有重要影响。本试验以85中33和豫麦49的101份F7代品系为材料,利用间苯三酚-冰醋酸法对小麦籽粒中的总阿拉伯糖基木聚糖和水溶性阿拉伯糖基木聚糖含量进行了测试,并对其硬度基因型进行了鉴定。为消除己糖的影响,测定阿拉伯糖基木聚糖时的波长为552nm和510nm。方差分析表明,基因型和环境对小麦籽粒水溶性阿拉伯糖基木聚糖含量均具有极显著影响,而总阿拉伯糖基木聚糖含量则受环境影响更大,二者均不符合正态分布。另外,Pi-na-D lb类型水溶性阿拉伯糖基木聚糖含量显著高于野生型,表明puroindoline基因是影响水溶性阿拉伯糖基木聚糖含量的一个重要因素。本研究为阿拉伯糖基木聚糖含量测试提供了一种较为快速和准确的方法,其遗传分析则为阿拉伯糖基木聚糖的标记研究提供了一定的理论依据,从而为我国小麦品质改良提供信息。     

Extraction and chemical characterization of rye arabinoxylan and the effect of β-glucan on the mechanical and barrier properties of cast arabinoxylan films

Water-extractable hemicellulose (WEH) fractions, containing approximately 65% arabinoxylans (WE-AX) and 20% mixed-linkage β-glucans were isolated from rye bran. In addition, water-extractable mixed-linkage β-glucans (BG) were isolated from oat bran as a reference material. The β-glucan content of the rye hemicellulose isolate was reduced to less than 5% by a selective lichenase treatment. Rye hemicelluloses, WEH and WE-AX had arabinose-to-xylose ratios of 0.54 and 0.57 and weight-average molecular weights (M_w) of 270 000 and 232 000 g/mol respectively. The M_w of BG was higher at 386 000 g/mol. The material properties of films prepared from the rye hemicellulose isolate and WE-AX as such, or with varying amounts of added BG (20:80; 50:50; 80:20 ratios) were studied. Prior removal of β-glucan from the isolate decreased the tensile strength of the films significantly as well as the elongation at break. Addition of BG to the purified WE-AX resulted in an increase in the tensile strength and elongation at break of the films. In contrast, the presence of BG had no clear effect on the oxygen permeability of the films. Both pure rye WE-AX and pure BG films showed excellent oxygen barrier properties (between 0.9 and 1.0 cm³ μm/m² d kPa). However, the water vapor permeability increased with addition of increasing amounts of BG to WE-AX. To our knowledge, this is the first study on the effect of β-glucans on the material and permeability properties of arabinoxylan-based films.     

Production and characterisation of two wheat-bran fractions: an aleurone-rich and a pericarp-rich fraction

Wheat bran is a good source of dietary fibre in the form of cell walls, but contains a number of different cell types. We describe a large-scale procedure for the production of an aleurone-rich and a pericarp-rich fraction from hard, Australian wheat. The fractions were characterised by field-emission scanning electron microscopy, by using a range of bright-field stains, colour reagents, and fluorochromes, and by chemical analysis of the walls. The aleurone fraction included the seed coat with its cuticle. Only the pericarp walls showed a histochemical reaction for lignin. The concentrations of ester-linked ferulic acid and (1-->3),(1-->4)-beta-glucans were greater in the aleurone-rich fraction than in the pericarp-rich fraction. The results are consistent with the arabinoxylans in the walls of the pericarp-rich fraction being more highly substituted with arabinose than those in the walls of the aleurone-rich fraction. When the fractions were fed as a dietary supplement to rats and walls were isolated from the faeces, it was found that the pericarp walls were not degraded, but the aleurone walls were partially degraded.     

Maize processing waste water arabinoxylans: Gelling capability and cross-linking content

Water-soluble feruloylated arabinoxylans were extracted from maize processing waste water (nejayote) generated from tortilla-making industries. Nejayote arabinoxylans (NAX) presented a ferulic acid content of 0.23 μg/mg, an arabinose to xylose ratio (A/X) of 0.65, an intrinsic viscosity, [η], of 183 ml/g and a molecular weight (Mw) of 60 kDa. Laccase-induced gels were obtained from 4% (w/v) NAX solution while, at lower concentrations, no gelation was observed. Laccase covalent cross-linking of NAX led to the formation of diferulic (di-FA) and triferulic (tri-FA) acid structures. 4% (w/v) NAX gel presented di-FA and tri-FA contents of 0.02 and 0.01 μg/mg NAX, respectively, and a G′ value of 2 Pa. Recuperation of this gum from a low-value maize by-product could represent a commercial advantage over other gums commonly used in the food industry.     

Structural and Enzymic Changes in Germinated Barley and Rye

Germination of barley and rye grains at 15°C and 56% moisture content resulted in the production of α-amylase, β-glucanase, endo-β-xylanase and α-arabinosidase. During germination of rye, enzyme activity increased significantly after the first day, whereas in the case of barley a rapid increase was not observed until after the third or fourth day. Rye varieties produced more xylanase, whereas barley produced more α-amylase and β-glucanase. Of the barley samples, germinated Pokko had the highest activities of β-glucanase, xylanase and α-amylase, and at 46% moisture content highest degradation of cell walls on the basis of image analysis. Arve had the highest α-arabinofuranosidase activity. Of the rye samples, Amando produced more xylanase and α-arabinosidase than Anna. The M_w of barley and rye β-glucan decreased significantly during germination. In rye samples, residual high molecular weight arabinoxylans were still present after 4 days of germination. The mass average molecular weight (M_w) of this fraction was 3 × 10⁶.     

Use of selected sourdough lactic acid bacteria to hydrolyze wheat and rye proteins responsible for cereal allergy

This work was aimed at showing the capacity of selected sourdough lactic acid bacteria to hydrolyze wheat and rye allergens. Hydrolysis was investigated after wheat sourdough fermentation and after treatment of wheat and rye sourdough breads with pepsin, trypsin and pancreatin, which mimicked the digestive process. As shown by immunoblotting with sera from allergic patients, wheat sourdough fermentation caused the disappearance of some IgE-binding proteins (albumins/globulins and gliadins mainly) with respect to the chemically acidified dough used as the control. The IgE-binding protein profile of wheat and rye sourdough breads differed from those of baker's yeast breads. The signals of the IgE-binding proteins contained in the sourdough breads disappeared after in vitro digestion with pepsin, trypsin and pancreatin. The same effect by digestive enzymes was not found for baker's yeast breads which showed persistent IgE-binding proteins. As shown by ELISA inhibition assays, the presence of IgE-binding low molecular weight proteins/peptides in sourdough breads significantly decreased with respect to baker's yeast breads. Proteolytic activity by selected sourdough lactic acid bacteria may have an importance during food processing to produce pre-digested wheat and rye dough which contains IgE-binding proteins degradable by digestive enzymes.     

Structure and physicochemical properties of β-glucans and arabinoxylans isolated from hull-less barley

The molecular characteristics of β-glucans and arabinoxylans from selected hull-less barleys were examined following their sequential extraction with water (45 and 95 °C), Ba(OH)₂, Ba(OH)₂/H₂O, and NaOH which resulted in five distinct fractions designated as WE45, WE95, Ba(OH)₂, Ba(OH)₂/H₂O, and NaOH, respectively. Both water-extractable fractions consisted mainly of β-glucans but up to 20% of arabinoxylans were found in WE45 of normal and high amylose barley varieties. Analysis of the water-extractable β-glucans, indicated differences in molecular features (weight average molecular weight (M_w), β-(1→4) to β-(1→3) linkage ratios, and amounts of cellulosic regions along the β-glucan chain) between WE45 and WE95, and among β-glucans from different cultivars. The variation observed in the viscoelastic behaviour of WE45 and WE95 fractions confirmed differences in the molecular weight among water-extractable β-glucans derived from various barley cultivars.Differences in the structure of arabinoxylans from the various fractions and cultivars were also observed. Water-extractable arabinoxylans (WE45 and WE95 fractions) had significantly lower xylose to arabinose (Xylp/Araf) ratios (1.47 and 1.52) than those extracted with Ba(OH)₂ (1.70), implying a greater degree of branching in the more readily soluble fractions. Small varietal differences in molecular weight (M_w), root mean square radius (R_g), and polydispersity (M_w/M_n) among Ba(OH)₂ fractions correlated with the substitution pattern of the xylan backbone.     

阿魏酸对小麦淀粉理化特性的影响

以小麦淀粉为原料,分别通过扫描电镜分析、傅里叶红外图谱分析、X-衍射图谱分析、差示扫描量热仪分析及快速黏度测试仪(RVA)分析,研究了添加0、5%、10%、15%、20%(w/w淀粉干基)阿魏酸后小麦淀粉的微观形貌、结晶性质、热力学特性及糊化特性。结果表明:随着阿魏酸含量的增加,淀粉表面不规程度增加,致密性降低;阿魏酸添加量至10%时,T₀(糊化初始温度)、T_P(糊化峰值温度)、T_C(糊化最终温度)和ΔH(糊化焓值)发生显著降低(p<0.05),说明阿魏酸的添加降低了小麦淀粉的稳定性;红外光谱表明,添加阿魏酸后,小麦淀粉在(1045/1022) cm^-1峰强度比值减小,说明添加阿魏酸后小麦淀粉有序性降低;X-衍射图谱表明,糊化后小麦淀粉由原来的A型变为B+V型,并表现出酸的衍射峰明显,说明阿魏酸与小麦淀粉未形成包合物。RVA分析表明,添加阿魏酸降低了小麦淀粉的峰值粘度、保持粘度、最终粘度和回升值降低,而崩解值增大,说明阿魏酸抑制了小麦淀粉的老化进程,扫描电镜分析也证明了阿魏酸抑制了淀粉的老化过程。     

Isolation, modification and characterization of soluble arabinoxylan fractions from rye grain

Because of the positive role of arabinoxylans and especially their water-soluble fractions in establishing bread properties, it seems reasonable to use them as natural bread improvers. In this work, an adequate isolation procedure of water-soluble arabinoxylans from rye grain with efficient purification steps is presented, delivering 2.9?% yield from wholemeal with a content of arabinoxylan of approximately 70?% and an arabinose/xylose ratio of 0.7. Furthermore, soluble arabinoxylans were modified by enzymatic hydrolyses, cross-linking with peroxidase/H₂O₂ treatment and combination of both for developing preparations applicable for bread making with different quality profiles. Additionally, a detailed analysis of chemical composition and molecular dimension was carried out by HPLC, SEC, HPSEC and viscosity measuring. The preparation after cross-linking showed considerably higher molar mass values, lower solubility and higher viscosity with high Huggin??s constant compared to the not modified sample. Otherwise, the combination of enzymatic hydrolysis and cross-linking resulted in the formation of arabinoxylan preparations with only slight degree of cross-linking and properties comparable with the only hydrolyzed sample.     

Degradation of cereal bran polysaccharide-phenolic acid complexes by Aspergillus niger CFR 1105

Cereal brans such as wheat and rice are abundant sources for obtaining bioactive phenolic compounds such as ferulic and coumaric acids, in turn these can be bio-transformed into high value flavour compounds such as vanillin. Aspergillus niger CFR 1105, found to induce greater amounts of cell wall degrading enzymes, was inoculated into wheat and rice brans, and grown for 24, 48, 72 and 96 h to understand the degradation pattern of non-starch polysaccharides and phenolic acid complexes. Native wheat bran polysaccharides mainly consisted of arabinose, xylose, galactose, and glucose, in % of 27:39:2:30, with traces of mannose, whereas rice bran consisted of arabinose, xylose, galactose, and glucose in % of 9:27:31:32, respectively. Both the cereal bran arabinoxylans were degraded extensively by A. niger at 96 h, whereas the degradation of 1,3/1,4-β-d-glucans and cellulose was negligible. Bound phenolic acids of rice and wheat brans identified by HPLC were found to be mainly ferulic, coumaric, syringic acids in % of 93.6:6.3:0 (wheat), 34.7:55.8:9.5 (rice) and were drastically degraded/utilized at 96 h. The above results have indicated preferential degradation of arabinoxylans of wheat bran by A. niger, which can be exploited to obtain bioactive compounds such as ferulic acid.