Water-extractable Arabinoxylan Research Articles

Changes in the arabinoxylan fraction of wheat grain during alcohol production.

Laboratory produced DDGS samples were compared with commercial samples from a distillery and a biofuel plant. Changes in structure, solubility and content of arabinoxylan (AX) was determined. The distillation process results in a relative increase of AX content compared to the starting material. The heating and drying processes involved in the production of DDGS lead to an increased solubility and viscosity of water-extractable AX. Production of DDGS results in structural changes to the AX. There is a decrease in 2- and 3-linked arabinose oligosaccharides, that contributes to around a 50% reduction in arabinosylation in DDGS compared with the starting grains. The current study shows that laboratory-scale DDGS provide an accurate representation of the commercial scale and that the AX composition of DDGS is consistently uniform irrespective of starting material. The uniformity of DDGS and thin stillage makes them a good potential source of AX for production of prebiotics or other novel products.

Impact of solid state fermentation on nutritional, physical and flavor properties of wheat bran

To improve the nutritional, physical and flavor properties of wheat bran, yeast and lactic acid bacteria (LAB) were used for fermenting wheat bran in solid state. Appearance properties, nutritional properties, microstructure, hydration properties and flavor of raw bran and fermented bran were evaluated. After treatments, water extractable arabinoxylans were 3–4 times higher than in raw bran. Total dietary fiber and soluble dietary fiber increased after solid state fermentation. Over 20% of phytic acid was degraded. Microstructure changes and protein degradation were observed in fermented brans. Water holding capacity and water retention capacity of fermented brans were improved. Results suggest that solid state fermentation is an effective way to improve the properties of wheat brans.

Molecular characterization of water extractable arabinoxylans isolated from wheat fine bran and their effect on dough viscosity

Water extractable arabinoxylans (WE-AXs) from different tissues of wheat exhibit large natural variations in their structure and are the basis of the functional properties of wheat in bread dough. The objective of this work was to characterize the molecular features of fine bran WE-AXs from two wheat genotypes (Triticum aestivum and T. durum) grown in field trials in Northwest Mexico, and explore their effect on the viscosity of flour-fine bran doughs. The monosaccharide composition and spatial arrangement of WE-AXs were influenced by wheat genotype and determined their molecular characteristics. Durum fine bran WE-AXs showed a low degree of substitution. Fine bran WE-AXs showed also a wider range of molecular sizes than the flour. The thermal stability of the WE-AXs were in the following order: durum fine bran < aestivum fine bran, and < flour. The lower arabinose/xylose substitution of WE-AXs was in accordance to high intrinsic viscosity, and produced a higher extensional viscosity of flour-fine bran doughs. These findings provide an additional knowledge about other important factors that affect the rheological properties of the dough, such as WE-AXs structure, which appears to play a more important role than expected.

Compositional Changes and Baking Performance of Rye Dough As Affected by Microbial Transglutaminase and Xylanase.

Doughs supplemented with endoxylanase (XYL) and varying amounts of microbial transglutaminase (TG) were analyzed by sequential protein extraction, quantitation of protein fractions and protein types, and determination of water-extractable arabinoxylans. With increasing TG activity, the concentration of prolamins and glutelins decreased and increased, respectively, and the prolamin-to-glutelin ratio strongly declined. The overall amount of extractable protein decreased with increasing TG level showing that cross-linking by TG provided high-molecular-weight protein aggregates. The decrease of the high-molecular-weight arabinoxylan fraction and the concurrent increase of the medium-molecular-weight fraction confirmed the degradation of arabinoxylans by XYL. However, XYL addition did not lead to significant improved cross-linking of rye proteins by TG. Volume and crumb hardness measurements of bread showed increased protein connectivity induced by XYL and TG. Significant positive effects on the final bread quality were especially obtained by XYL addition.

Interaction between gluten proteins and their mixtures with water-extractable arabinoxylan of wheat by rheological, molecular anisotropy and CP/MAS 13C NMR measurements

In this study, water-extractable arabinoxylan, WEAX, of wheat was isolated and mixed with gluten to observe small and large strain behavior and microscopic structure of the mixtures. The results showed that WEAX improves the viscoelasticity of gluten and makes the microscopic structure of gluten less compact. Free sulfhydryl, fluorescence anisotropy and CP/MAS 13C NMR measurements were used to gain a better understanding of the interactions between WEAX and gluten proteins of wheat. It was demonstrated that when gluten was mixed with WEAX, the free –SH of gluten proteins cross-linked to each other or to WEAX. The cross-linking happened mainly to LMW-GS. It was shown from the fluorescence anisotropy that the conformation of glutenin was more greatly influenced by WEAX than gliadin because of the difference in their molecular conformation. In addition, it was found in this study that tyrosine groups of glutenin also played an important role in the interactions between WEAX and gluten.

Application of model bread baking in the examination of arabinoxylan—protein complexes in rye bread

The changes in molecular mass of arabinoxylan (AX) and protein caused by bread baking process were examined using a model rye bread. Instead of the normal flour, the dough contained starch, water-extractable AX and protein which were isolated from rye wholemeal. From the crumb of selected model breads, starch was removed releasing AX-protein complexes, which were further examined by size exclusion chromatography.On the basis of the research, it was concluded that optimum model mix can be composed of 3–6% AX and 3–6% rye protein isolate at 94–88% of rye starch meaning with the most similar properties to low extraction rye flour.Application of model rye bread allowed to examine the interactions between AX and proteins. Bread baked with a share of AX, rye protein and starch, from which the complexes of the highest molar mass were isolated, was characterized by the strongest structure of the bread crumb.

Characterization of water and alkali extractable arabinoxylan from wheat and rye under standardized conditions.

Arabinoxylans (AXs) are an important component of wheat and rye dough. They bind water, contribute to the formation of viscous dough and improve the quality of bread. For the application of AX fractions in bread making process, it is useful to record a quality profile of wheat fractions compared to the quality profile of rye fractions under standardized conditions. In this work water and alkali extractable AX containing fractions, from wheat- and rye wholemeal, were extracted under standardized conditions and characterized. For analysis of composition, structural features, and molecular dimension a combination of chemical, physicochemical, enzymatic and chromatographic techniques was applied. The molar mass distributions obtained by means of an innovative colorimetric pentose detection in the eluted SEC fractions were comparable for all under standardized conditions extracted AXs. The determined molar masses of AXs extracted both from wheat- and from rye grain were close to 2.0×10(5)g/mol for water extractable AXs and 3.0×10(5)g/mol for alkali extractable AXs. Different susceptibility to endoxylanase treatment, having been observed as differences in the SEC profiles, may be evidence of structural differences between AXs depending on their origin. The viscosities of AX solutions were strongly influenced by their molar mass and structure; samples being less susceptible to endoxylanase provided solutions of higher viscosity.

Impact of water extractable arabinoxylan from rye bran on the frozen steamed bread dough quality

Impact of water extractable arabinoxylan from rye bran on frozen steamed bread dough quality was investigated in terms of the bread characteristics, ice crystallization, yeast activity as well as the gluten molecular weight distribution and glutenin macropolymer content in the present study. Results showed that water extractable arabinoxylan significantly improved bread characteristics during the 60-day frozen storage. Less water was crystallized in the water extractable arabinoxylan dough during storage, which could explain the alleviated yeast activity loss. For all the frozen dough samples, more soluble high molecular weight (Mw≈91,000–688,000) and low molecular weight (Mw≈91,000–16,000) proteins were derived from glutenin macropolymer depolymerization. Nevertheless, water extractable arabinoxylan dough developed higher glutenin macropolymer content with lowered level of soluble low molecular weight proteins throughout the storage. This study suggested water extractable arabinoxylan from rye bran had great potential to be served as an effective frozen steamed bread dough improver.

Adjuvant properties of water extractable arabinoxylans with different structural features from wheat flour against model antigen ovalbumin.

Despite the numerous benefits of AX on the immune system and gut bacteria, the potential adjuvant activity of WEAX on immune responses has not been adequately investigated. In the present study, three kinds of WEAX with different structural features were obtained and their adjuvant potential on the specific cellular and humoral immune responses in ovalbumin (OVA) immunized mice were assessed. Our data demonstrated that WEAX had potent effects on innate and acquired immune responses through up-regulating the NK cell activation and promoting the Th2 type immune response. Furthermore, this study also elucidated the possible relationship between the adjuvant activity of WEAX and the structure. Compared with the other characteristics of the WEAX, we found that the immunomodulatory activity may be related to their content of ferulic acid, and not to the molecular weight.

POD promoted oxidative gelation of water-extractable arabinoxylan through ferulic acid dimers. Evidence for its negative effect on malt filterability

As a major component of non-starch polysaccharide in barley, arabinoxylan (AX) plays an important role in quality traits of malt and the final beer product. The Chinese barley malt has encountered filterability problems for a long time. The main reason caused by barley cultivar has been accepted in the malting and brewing industries. In our previous proteomic study, the peroxidase (POD) BP1 was found to be in quite high abundant in the filterability defect Chinese barley malt. Therefore, the present study tried to verify its negative effect on filterability, by surveying its activity in different malt samples and detecting effects of POD on AX gelation and filterability. The results showed that the activity of POD, as well as the content of AX bounded ferulic acid, were both negatively correlated with filterability, while the feruloyl esterase activity was positively correlated with it. In addition, AX gelation catalyzed by POD caused worse filterability, and the natural inhibitor of POD, vitamin C, could blocked the cross linking catalyzed by POD and thus improve the filterability. These results all suggested the great negative effect of POD on malt filterability.

QTL mapping of grain arabinoxylan contents in common wheat using a recombinant inbred line population

Arabinoxylans (AX) are major polymers of wheat grain cell walls and affect the end-use properties and nutritional quality. Total (TOT-AX), water-unextractable (WU-AX), and water-extractable (WE-AX) AX contents were determined in grain of 240 recombinant inbred wheat lines (RILs), derived from the cross PH82-2/Neixiang 188. A total of 195 SSR and STS markers were used to construct a genetic map and to detect quantitative trait loci (QTL). Wide ranges of variation in TOT-AX, WU-AX, and WE-AX contents were observed among the RILs, with line effects contributing the largest phenotypic variation. Broad sense heritabilities (h 2) were 0.50, 0.38 and 0.71, respectively. Inclusive composite interval mapping (ICIM) identified four additive QTL for TOT-AX content on chromosomes 1B, 1D, 3B and 5B, explaining 3.7–14.6 % of the phenotypic variance (PV), among which two were involved in significant additive × season interactions, contributing 0.5–2.4 % of the PV. Two additive QTL for WU-AX content were identified on chromosomes 1B and 1D, accounting for 6.4 and 8.6 % of the PV, respectively; both were involved in significant additive × season interactions, contributing 0.6–1.4 % of the PV. Nine additive QTL for WE-AX content were identified on chromosomes 1A, 1B, 2B, 3B, 5A, 5B, 6B, 7A and 7B, explaining 3.8–15.2 % of the PV, and three of them were involved in significant additive × season interactions, contributing 0.5–2.1 % of the PV. Two pairs of epistatic QTL, with significant epistatic × season interactions, were identified for TOT-AX and WU-AX contents, contributing 16.6 and 18.6 % of the PV, respectively. The QTL identified on chromosomes 1B (associated with rye secalin marker sec1), 5A, 5B and 7A showed stable effects on WE-AX content across seasons.

Application of cross-linked and hydrolyzed arabinoxylans in baking of model rye bread

The role of water extractable arabinoxylan with varying molar mass and structure (cross-linked vs. hydrolyzed) in the structure formation of rye bread was examined using a model bread. Instead of the normal flour, the dough contained starch, arabinoxylan and protein, which were isolated from rye wholemeal. It was observed that the applied mixes of these constituents result in a product closely resembling typical rye bread, even if arabinoxylan was modified (by cross-linking or hydrolysis).The levels of arabinoxylan required for bread preparation depended on its modification and mix composition. At 3% protein, the maximum applicable level of poorly soluble cross-linked arabinoxylan was 3%, as higher amounts of this preparation resulted in an extensively viscous dough and diminished bread volume. On the other hand highly soluble, hydrolyzed arabinoxylan could be used at a higher level (6%) together with larger amounts of rye protein (3% or 6%). Further addition of arabinoxylan leads to excessive water absorption, resulting in a decreased viscosity of the dough during baking and insufficient gas retention.

Effect of enzymatic and technological treatments on solubilisation of arabinoxylans from brewer's spent grain

Brewer's spent grain (BSG), the most abundant brewing by-product, has hidden and underexploited nutritional potential. In order to valorize BSG, the effects of three commercial xylanases and a peptidase on water unextractable arabinoxylans (WUAX) were studied. Comparing all treatments, higher addition of xylanase resulted in an increase in water extractable arabinoxylans (WEAX). In the most efficient treatment, xylanase alone was able to solubilise 23.7% of WUAX, while the peptidase showed no effect. However, when added together with xylanase, peptidase increased the solubilisation of WUAX up to 1.6 folds. A positive correlation between particle size reduction and solubilisation of WUAX was also proved through milling BSG. These results suggest that access to xylan backbone increases with proteolytic activities, proving a synergistic effect of these specific enzymes. Therefore, if properly treated before being added as ingredient, BSG could add health functionalities to foodstuff while reducing the environmental impact of brewing industries.

Covalently Cross-Linked Arabinoxylans Films for Debaryomyces hansenii Entrapment.

In the present study, wheat water extractable arabinoxylans (WEAX) were isolated and characterized, and their capability to form covalently cross-linked films in presence of Debaryomyces hansenii was evaluated. WEAX presented an arabinose to xylose ratio of 0.60, a ferulic acid and diferulic acid content of 2.1 and 0.04 µg∙mg−1 WEAX, respectively and a Fourier Transform Infra-Red (FT-IR) spectrum typical of WEAX. The intrinsic viscosity and viscosimetric molecular weight values for WEAX were 3.6 dL∙g−1 and 440 kDa, respectively. The gelation of WEAX (1% w/v) with and without D. hansenii (1 × 107 CFU∙cm−2) was rheologically investigated by small amplitude oscillatory shear. The entrapment of D. hansenii decreased gel elasticity from 1.4 to 0.3 Pa, probably by affecting the physical interactions between WEAX chains. Covalently cross-linked WEAX films containing D. hansenii were prepared by casting. Scanning electron microscopy images show that WEAX films containing D. hansenii were porous and consisted of granular-like and fibre microstructures. Average tensile strength, elongation at break and Young’s modulus values dropped when D. hansenii was present in the film. Covalently cross-lined WEAX containing D. hansenii could be a suitable as a functional entrapping film.

Quantification and visualization of dietary fibre components in spelt and wheat kernels

This study was undertaken to determine contents and structural characteristics of arabinoxylan (AX), fructan and β-glucan in 28 spelt accessions, and to compare them with those of dietary fibre components in 11 wheat accessions. In addition, microscopic visualization of AX and β-glucan distribution in a selection of these accessions was performed. On average, wheat contained more total AX (TOT-AX; 6.90 versus 5.74%) and water-extractable AX (WE-AX; 0.71 versus 0.59%) than spelt. The overall arabinose to xylose ratio (A/X; 0.72 for wheat and 0.71 for spelt) was similar for both subspecies, but that of water extractable material was higher for spelt than for wheat (1.25 versus 0.97). Fructan content and degree of polymerization (DP) were lower in spelt than in wheat (fructan content; 1.29% versus 1.53% and DP; 3.3 versus 4.5). β-glucan content was similar for both subspecies (0.54% for spelt and 0.51% for wheat). In the spelt accessions, the contents of the different fibre components significantly differed (up to 74% difference) between accessions and countries of origin, but were not affected by accession status and bread making quality. Microscopic visualizations showed that the two subspecies are very similar in terms of dietary fibre distribution over the kernel cell walls.

Study of hydration properties of wheat bran as a function of particle size

New insights in the hydration properties of wheat bran as function of particle size were gained based on a novel water retention capacity test. Upon milling coarse bran with an average particle size of 1687μm down to 77μm, the specific surface increases by twofold, structural integrity was lost and water extractable arabinoxylan and damaged starch content were practically unaffected. A standard centrifugation-based water retention capacity, swelling capacity and Enslin–Neff absorption test showed up to threefold higher water absorption for large particles. During these hydration tests, bran is not (continuously) subjected to external forces which allows larger particles to hold more water in between bran particles and probably in micropores. In contrast, the water retention capacity as determined by a novel drainage centrifugation method, and Farinograph absorption were not affected by particle size. In these methods, continuous exposure of bran to external forces causes bran to retain only strongly bound water which is most likely bound in cell wall nanopores and through hydrogen bonding. These insights reconcile contradicting observations in literature with regard to this matter.

Wheat dough rheology at low water contents and the influence of xylanases

The effect of low water contents and xylanases on wheat dough rheology is reported. Farinograph, dynamic oscillation, and creep-recovery measurements were performed using water concentrations from 34 to 44.8% (total basis). A water reduction from 43.5–44.8% to 34% increased resistance upon mixing as evidenced by higher Farinograph Brabender Unit values, increased G′ and G″-values, and decreased the maximum creep compliance by 1–2 orders of magnitude. Addition of an endoxylanase with a higher selectivity for water-unextractable arabinoxylans and an endoxylanase with a higher selectivity for water-extractable arabinoxylans both resulted in lower G′ and Farinograph dough consistencies and an increase in maximum creep compliance. The major influence of both xylanases was the release of water with possible water reductions of 2–5% (on water basis), though no distinct differences between the two xylanases were observed.

Study of the Chemical Changes and Evolution of Microbiota During Sourdoughlike Fermentation of Wheat Bran

ABSTRACTSeveral studies have emphasized the possibility of enhancing nutritional properties of cereal by‐products through biotechnological processes. Bran fermentation positively affects the bioavailability of several functional compounds. Moreover, bran fermentation could increase water‐extractable arabinoxylans (WEAX), compounds with positive effects on glucose metabolism and prebiotic properties. This study was aimed at increasing the amount of bran bioactive compounds through a sourdoughlike fermentation process. Wheat bran fermentations were conducted through continuous propagation by back‐slopping of fermented bran (10% inoculum) until a stable microbiota was established, reaching high counts of lactic acid bacteria and yeasts (109 and 107 CFU/g, respectively). At each refreshment step, bacterial strains were isolated, clustered, molecularly analyzed by randomly amplified polymorphic DNA, and identified at the species level by 16S rRNA gene sequencing. Leuconostoc mesenteroides, Lactobacillus brevis, Lactobacillus curvatus, Lactobacillus sakei, Lactobacillus plantarum, Pediococcus pentosaceus, and Pichia fermentans dominated the stable sourdough ecosystem. After fermentation, levels of soluble fiber increased (+30%), and WEAX and free ferulic acid were respectively fourfold and tenfold higher than in raw bran, results probably related to microbial xylan‐degrading activity, whereas phytic acid was completely degraded. These preliminary data suggest that fermented bran could be considered an interesting functional ingredient for nutritional enhancement.

The Effect of Extrusion Conditions on Water-extractable Arabinoxylans from Corn Fiber.

The effect of feed moisture contents (30%, 40%, and 50%) and screw speed (200 rpm, 250 rpm, and 300 rpm) on the corn fiber gum (CFG) yield and soluble arabinoxylans (SAX) content of destarched corn fiber was investigated. The CFG yields and SAX contents of extruded, destarched corn fiber were higher than that of destarched corn fiber. In extruded, destarched corn fiber, increased screw speed and decreased feed moisture contents resulted in a higher SAX contents. The maximum yields of CFG obtained from extruded, destarched corn fiber were 79.1±19.0 g/kg (30% feed moisture content) and 82.3±11.30 g/kg (300 rpm screw speed). The highest SAX content was also observed at a screw speed of 300 rpm. The results of the present study show that water extraction and extrusion combined have the potential to increase CFG and SAX yields from corn fiber.

Shear-induced starch–gluten separation at very low water content aided by xylanases

This study examines the influence of extremely low water content on shear-induced starch–gluten separation and how endoxylanases influence the separation by releasing water associated with arabinoxylan. Shearing was performed at a water content ranging from 34% to 43.5% (w/w). It was possible to concentrate gluten to 60% protein content in local gluten clusters and most of the concentration occurred within 5min. Contrary to higher water concentrations, a water content <40% resulted in local separation of starch and gluten but no inward migration of the gluten. Addition of an endoxylanase with a higher selectivity for water-unextractable arabinoxylans and an endoxylanase with a higher selectivity for water-extractable arabinoxylans both resulted in a significant reduction in torque. The major influence of xylanase was the release of 3–5% water (on a water basis), allowing separation at even lower water content. Furthermore, no significant differences were found between the enzymes.