Water-extractable Arabinoxylan Research Articles

Content and molecular weight of water-extractable arabinoxylans in wheat malt and wheat malt-based wort with different Kolbach indices

Arabinoxylans (AXs) are partially water-extractable polymers that cause problems of viscosity and filterability during beer brewing. This study investigated the effects of Kolbach index (KI) on water-extractable AXs (WEAXs). KI had positive correlations with extract (r = 0.845) and free amino nitrogen (FAN) (r = 0.958). The contents of malt WEAXs (WEAXsm), total AXs and wort AXs (WAXs) were 10.8-11.6 g kg⁻¹, 57.5-60.8 g kg⁻¹ and 137.5-140.5 mg per 100 mL respectively and the corresponding arabinose/xylose (A/X) ratios were 0.52-0.56, 0.55-0.62 and 0.48-0.50. The molecular weight (Mw) ranged from 4.92 × 10⁴ to 6.93 × 10⁴ Da for WEAXsm and from 1.24 × 10⁴ to 2.90 × 10⁴ Da for WAXs. KI had negative correlations with the average degree of polymerization (avDP) of malt (r = -0.877) and wort (r = -0.978). Wort viscosity showed a positive correlation with the Mw of WEAXsm (Mwm) (r = 0.821). Increasing KI can promote the degradation of the xylan backbone, while it cannot affect the branching of the polymer chain and the content and Mw of WEAXs.

Entrapment of Probiotics in Water Extractable Arabinoxylan Gels: Rheological and Microstructural Characterization

Due to their porous structure, aqueous environment and dietary fiber nature arabinoxylan (AX) gels could have potential applications for colon-specific therapeutic molecule delivery. In addition, prebiotic and health related effects of AX have been previously demonstrated. It has been also reported that cross-linked AX can be degraded by bacteria from the intestinal microbiota. However, AX gels have not been abundantly studied as carrier systems and there is no information available concerning their capability to entrap cells. In this regard, probiotic bacteria such as Bifidobacterium longum have been the focus of intense research activity lately. The objective of this research was to investigate the entrapment of probiotic B. longum in AX gels. AX solution at 2% (w/v) containing B. longum (1 × 107 CFU/cm) formed gels induced by laccase as cross-linking agent. The entrapment of B. longum decreased gel elasticity from 31 to 23 Pa, probably by affecting the physical interactions taking place between WEAX chains. Images of AX gels containing B. longum viewed under a scanning electron microscope show the gel network with the bacterial cells entrapped inside. The microstructure of these gels resembles that of an imperfect honeycomb. The results suggest that AX gels can be potential candidates for the entrapment of probiotics.

Genotypic and Environmental Variations of Arabinoxylan Content and Endoxylanase Activity in Barley Grains

Arabinoxylan (AX) content in barley grains is an important quality determinant when barley is used as raw material of malt or beer production. The cultivar and environmental variations of total arabinoxylan (TAX), water extractable arabinoxylan (WEAX) and endoxylanase activity (EA) were investigated using eight barley cultivars growing at seven locations with diverse environmental conditions. The results showed that both barley cultivar and location significantly affected the TAX, WEAX and EA levels, but the variations of TAX content and EA were mainly attributed to cultivar, while the impact of location on WEAX content was greater than that of cultivar. Correlation analysis indicated that TAX was significantly correlated to WUAX.

Mode of endosperm and wholemeal arabinoxylans solubilisation during rye breadmaking: Genotypic diversity in the level, substitution degree and macromolecular characteristics

Insight into solubilisation mechanisms of rye arabinoxylans during breadmaking is important for understanding the biochemical processes that affect bread attributes. Purified ethanol precipitated water-extractable arabinoxylans (WE-AX) and residual unextractable counterparts (WU-AX) were isolated from rye flours and resulting breads. While the endosperm flours had lower endoxylanase activities and higher arabinose-to-xylose ratios of WU-AX than those of corresponding wholemeals, there were not any significant differences between them in the mean amounts of WU-AX hydrolysed during breadmaking. Nevertheless, they were highly affected by rye cultivar used for breadmaking. On average, 42% and 36% of WU-AX were recovered in bread WE-AX fraction, causing its 11% and 8% increase, respectively for endosperm and wholemeal breads. Bread WE-AX, however, had lower molecular weights than those of starting flours, implying chains depolymerisation. Degree of AX solubilisation depends mainly on rye genotype used, determining combined effect of enzymatic and acid hydrolyses, associations and fine structure of AX.

Characterization of water extractable arabinoxylans from a spring wheat flour: rheological properties and microstructure.

In the present study water extractable arabinoxylans (WEAX) from a Mexican spring wheat flour (cv. Tacupeto F2001) were isolated, characterized and gelled and the gel rheological properties and microstructure were investigated. These WEAX presented an arabinose to xylose ratio of 0.66, a ferulic acid and diferulic acid content of 0.526 and 0.036 µg/mg WEAX, respectively and a Fourier Transform Infra-Red (FT-IR) spectrum typical of arabinoxylans. The intrinsic viscosity and viscosimetric molecular weight values for WEAX were 3.5 dL/g and 504 kDa, respectively. WEAX solution at 2% (w/v) formed gels induced by a laccase as cross-linking agent. Cured WEAX gels registered storage (G’) and loss (G’’) modulus values of 31 and 5 Pa, respectively and a diferulic acid content of 0.12 µg/mg WEAX, only traces of triferulic acid were detected. Scanning electron microscopy analysis of the lyophilized WEAX gels showed that this material resembles that of an imperfect honeycomb.

Molecular Features of Wheat Endosperm Arabinoxylan Inclusion in Functional Bread.

Arabinoxylan (AX) is a major dietary fibre component found in a variety of cereals. Numerous health benefits of arabinoxylans have been reported to be associated with their solubility and molecular features. The current study reports the development of a functional bread using a combination of AX-enriched material (AEM) and optimal commercial endoxylanase. The total AX content of bread was increased to 8.2 g per 100 g available carbohydrates. The extractability of AX in breads with and without endoxylanase was determined. The results demonstrate that water-extractable AX (WE-AX) increased progressively through the bread making process. The application of endoxylanase also increased WE-AX content. The presence of 360 ppm of endoxylanase had positive effects on the bread characteristics in terms of bread volume and firmness by converting the water unextractable (WU)-AX to WE-AX. In addition, the molecular weight (Mw) distribution of the WE-AX of bread with and without endoxylanase was characterized by size-exclusion chromatography. The results show that as the portion of WE-AX increased, the amount of high Mw WE-AX (higher than 100 kDa) decreased, whereas the amount of low Mw WE-AX (lower than 100 kDa) increased from 33.2% to 44.2% through the baking process. The low Mw WE-AX further increased to 75.5% with the application of the optimal endoxylanase (360 ppm).

Influence of malting conditions on sorghum (Sorghum bicolor (L.) Moench) as a raw material for fermented beverages

There has been recently increased interest in sorghum to substitute the gluten containing cereals in the diet of people suffering from celiac disease. The response surface methodology was used to determine the influence of malting parameters (degree of steeping, germination temperature and time) on sorghum (Sorghum bicolor (L.) Moench). Each parameter was varied at three levels. Malting attributes, considered important to produce high quality malt for the production of lactic acid fermented beverages, were analyzed. The optimized conditions were: degree of steeping 41%, germination temperature 27℃ after 7 days of germination. Under these conditions, the following values of the studied attributes can be obtained: α-amylase 139 U/g, β-amylase 60 U/g, extract 83.8%, free amino nitrogen 117.8 mg/100 g, Kolbach index 26.6%, water-extractable arabinoxylan 0.3 g/L and vitamin B2 114.9 µg/L. Among the tested parameters, the germination time had the highest effect on malting attributes. Although the activity of amylolytic enzymes α- and β-amylase were low, the value of extract was high and comparable to that of barley malt. The obtained results showed that sorghum malt is a promising raw material for the production of lactic acid fermented beverages.

Water Extractable Arabinoxylan Aerogels Prepared by Supercritical CO2 Drying

Water extractable arabinoxylan (WEAX) aerogels were prepared by extracting the solvent from the alcogels (WEAX hydrogels with an alcohol as the solvent) with carbon dioxide under supercritical conditions. WEAX aerogels were characterized using scanning electron microscopy and adsorption and desorption nitrogen isotherms. The micrographs indicate a heterogeneous porous network structure in WEAX aerogel. Adsorption/desorption nitrogen isotherms of this material were type IV, which confirm that this material possess a mesoporous structure. WEAX aerogels rehydration capability was evaluated and the water absorption mechanism was determined. The WEAX aerogels water absorption mechanism was non-Fickian (n = 0.54).

Depolymerization Degree of Water-Extractable Arabinoxylans in Rye Bread: Characteristics of Inbred Lines Used for Breeding of Bread Cultivars

The water-extractable arabinoxylans (WE AXs) present in rye bread govern its viscous properties, which may be related to reduced risk of cardiovascular diseases and diabetes. Breads made from rye cultivars generally exhibit higher AX-dependent extract viscosities (Cyran, M. R.; Saulnier, L. Food Chemistry2012, 131, 667-676) when compared with those produced from inbred lines used for their breeding. To give further details about this trend, the WE AXs were isolated from breads of lines and structurally characterized by HPSEC and (1)H NMR spectroscopy. The extract viscosities of endosperm and whole-meal breads were usually comparable, in contrast to those made from rye cultivars with higher viscosity of endosperm bread. The WE AXs present in breads obtained from inbred lines were characterized by the higher degradation degrees than those in breads from cultivars, as indicated by their HPSEC-RI profiles. This was associated with considerably lower proportions of 2-Xylp in their backbones. Besides, a level of endoxylanase activity in flours from inbred lines was much higher than that in flours from cultivars. Breeding of hybrid rye cultivars for production of high-viscosity bread requires the proper components. They may be preliminarily selected from populations with high WE AX contents and relatively low levels of endoxylanase activity by using the overall viscosity test for starting flours. However, further measurement of AX-dependent extract viscosity in test breads made from such lines may verify their usefulness completely.

Formation of Phenolic Microbial Metabolites and Short-Chain Fatty Acids from Rye, Wheat, and Oat Bran and Their Fractions in the Metabolical in Vitro Colon Model

Rye bran and aleurone, wheat bran and aleurone, and oat bran and cell wall concentrate were compared in their in vitro gut fermentation patterns of individual phenolic acids and short-chain fatty acids, preceded by enzymatic in vitro digestion mimicking small intestinal events. The formation of phenolic metabolites was the most pronounced from the wheat aleurone fraction. Phenylpropionic acids, presumably derived from ferulic acid (FA), were the major phenyl metabolites formed from all bran preparations. The processed rye, wheat, and oat bran fractions contained more water-extractable dietary fiber (DF) and had smaller particle sizes and were thus more easily fermentable than the corresponding brans. Rye aleurone and bran had the highest fermentation rate and extent probably due to high fructan and water-extractable arabinoxylan content. Oat samples also had a high content of water-extractable DF, β-glucan, but their fermentation rate was lower. Enzymatic digestion prior to in vitro colon fermentation changed the structure of oat cell walls as visualized by microscopy and increased the particle size, which is suggested to have retarded the fermentability of oat samples. Wheat bran was the most slowly fermentable among the studied samples, presumably due to the high proportion of water-unextractable DF. The in vitro digestion reduced the fructan content of wheat samples, thus also decreasing their fermentability. Among the studied short-chain fatty acids, acetate dominated the profiles. The highest and lowest production of propionate was from the oat and wheat samples, respectively. Interestingly, wheat aleurone generated similar amounts of butyrate as the rye fractions even without rapid gas production.

Prebiotic effects and intestinal fermentation of cereal arabinoxylans and arabinoxylan oligosaccharides in rats depend strongly on their structural properties and joint presence

Cereal arabinoxylan (AX) is one of the main dietary fibers in a balanced human diet. To gain insight into the importance of structural features of AX for their prebiotic potential and intestinal fermentation properties, a rat trial was performed. A water unextractable AX-rich preparation (WU-AX, 40% purity), water extractable AX (WE-AX, 81% purity), AX oligosaccharides (AXOS, 79% purity) and combinations thereof were included in a standardized diet at a 5% AX level. WU-AX was only partially fermented in the ceco-colon and increased the level of butyrate and of butyrate producing Roseburia/E. rectale spp. Extensive fermentation of WE-AX and/or AXOS reduced the pH, suppressed relevant markers of the proteolytic breakdown and induced a selective bifidogenic response. Compared with WE-AX, AXOS showed a slightly less pronounced effect in the colon as its fermentation was virtually complete in the cecum. Combining WU-AX and AXOS caused a striking synergistic increase in cecal butyrate levels. WU-AX, WE-AX and AXOS together combined a selective bifidogenic effect in the colon with elevated butyrate levels, a reduced pH and suppressed proteolytic metabolites. The prebiotic potential and fermentation characteristics of cereal AX depend strongly on their structural properties and joint presence.

Flour Mill Stream Blending Affects Sugar Snap Cookie and Japanese Sponge Cake Quality and Oxidative Cross‐Linking Potential of Soft White Wheat

The purpose of this research was to study the functional differences between straight grade (75% extraction rate) and patent (60% extraction rate) flour blends from 28 genetically pure soft white and club wheat grain lots, as evidenced by variation in sugar snap cookie and Japanese sponge cake quality. Functional differences were examined relative to arabinoxylan content, protein content, and oxidative cross-linking potential of flour slurries. Oxidative cross-linking measurements were obtained on flour slurries with a low shear Bostwick consistometer and considered endogenous oxidative cross-linking potential (water alone) or enhanced oxidative cross-linking potential (with added hydrogen peroxide-peroxidase). A 2-way ANOVA indicated that flour blend was the greater source of variation compared to grain lot for all response variables except water-extractable arabinoxylan content. Patent flours produced larger sugar snap cookies and Japanese sponge cakes, and contained significantly less total and water-unextractable arabinoxylans, protein, and ash than did straight grade flours. Patent flours produced more viscous slurries for endogenous and enhanced cross-linking measurements compared to the straight grade flours. The functional differences between patent and straight grade flours appear to be related to the particular mill streams that were utilized in the formulation of the 2 flour blends and compositional differences among those streams.

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.

Water‐Extractable Nonstarch Polysaccharide Distribution in Pilot Milling Analysis of Soft Winter Wheat

ABSTRACTCommercial wheat (Triticum aestivum em. Thell) flour milling produces flour streams that differ in water absorption levels because of variability in protein concentration, starch damaged by milling, and nonstarch polysaccharides. This study characterized the distribution of water‐extractable (WE) nonstarch polysaccharides (NSP) in long‐flow pilot‐milling streams of soft wheat to model flour quality and genetic differences among cultivars. Existing reports of millstream analysis focus on hard wheat, which breaks and reduces differently from soft wheat. Seven soft winter wheat genotypes were milled on a pilot‐scale mill that yields three break flour streams, five reduction streams, and two resifted streams. Protein concentration increased linearly through the break streams. WENSP concentration was low and similar in the first two break streams, which are the largest break streams. Flour recovery decreased exponentially through the reduction streams; flour ash and water‐extractable glucose and galactose polymers increased exponentially through the reduction streams. Protein concentration and WE xylan concentration increased linearly through the reduction streams. The ratio of arabinose to xylose in WE arabinoxylan (WEAX) decreased through the reduction streams, and response varied among the genotypes. Flour ash was not predictive of stream composition among genotypes, although within genotypes, ash and other flour components were correlated when measured across streams. The second reduction flour stream was the largest contributor to straight‐grade flour WEAX because of both the size of the stream and the concentration of WEAX in the stream.

Use of a global wheat core collection for association analysis of flour and dough quality traits

Flour and dough quality are very important breeding traits for wheat ( Triticum aestivum L.) the selection of which would benefit from linked molecular markers. Association analysis allows the identification of genes or quantitative trait loci (QTL) related to target traits. The effectiveness of this approach depends on the availability of a densely genotyped population with large genetic variability for the traits of interest. Our objective was to identify chromosomal regions associated with flour and dough quality traits using a core collection built by maximizing the genetic diversity and phenotypic variability. We investigated the association of DArT, SSR and SNP markers with grain protein content, grain hardness, water-extractable arabinoxylan (WEAX) viscosity, wholemeal flour color and dough rheology. Out of 803 markers tested, 130 markers spread over the genome were associated with at least one trait, varying from 20 associated with WEAX viscosity to 60 associated with dough quality. Most chromosome regions known to determine wheat quality from the study of several bi-parental recombinant inbred lines were confirmed here and some new regions were identified. Associations were found for each trait studied, demonstrating that the core collection is a useful tool for QTL association mapping of these and other traits of interest.

Spectroscopic Analysis of Diversity of Arabinoxylan Structures in Endosperm Cell Walls of Wheat Cultivars (Triticum aestivum) in the HEALTHGRAIN Diversity Collection

Fifty bread wheat (Triticum aestivum L.) cultivars were selected from the HEALTHGRAIN germplasm collection based on variation in their contents of total and water-extractable arabinoxylan. FT-IR spectroscopic mapping of thin transverse sections of grain showed variation in cell wall arabinoxylan composition between the cultivars, from consisting almost entirely of low-substituted arabinoxylan (e.g., T.aestivum 'Claire') to almost entirely of highly substituted arabinoxylan (e.g., T.aestivum 'Manital') and a mixture of the two forms (e.g., T.aestivum 'Hereward'). Complementary data were obtained using endoxylanase digestion of flour followed by HP-AEC analysis of the arabinoxylan oligosaccharides. This allowed the selection of six cultivars for more detailed analysis using FT-IR and (1)H NMR spectroscopy to determine the proportions of mono-, di-, and unsubstituted xylose residues. The results of the two analyses were consistent, showing that variation in the composition and structure of the endosperm cell wall arabinoxylan is present between bread wheat cultivars. The heterogeneity and spatial distribution of the arabinoxylan in endosperm cell walls may be exploited in wheat processing as it may allow the production of mill streams enriched in various arabinoxylan fractions which have beneficial effects on health.

Water-extractable arabinoxylan content in milling fractions of spring wheats Contenido de arabinoxilano extraíble en agua en fracciones pulverizadas de trigos de primavera

The core objective of the present investigation was to extract and determine water-extractable arabinoxylan (WEAX) content in spring wheat varieties and their milling fractions. WEAX was extracted by ethanol method and both monosaccharides (arabinose and xylose) were determined by gas chromatograph–mass spectrometer (GC/MS). The WEAX content in whole wheat flour and milling fractions of wheat varieties ranged from 6.9 to 12.1 g/kg and 3.6 to 7.9 g/kg, respectively. WEAX has negative impact on gluten quality as reduced gluten strength was observed. Moreover, adding WEAX in bread formulation resulted in significant increase in volume and improvement in texture of the final product. WEAX holds potential to be extracted and utilized in cereal-based products for best quality and value addition. El principal objetivo de la presente investigación fue extraer y determinar el contenido de arabinoxilanos extraíbles en agua en variedades de trigo de primavera y sus fracciones pulverizadas. Arabinoxilanos extraíbles en agua (WEAX) fueron extraídos con en método etanol y ambos monosacáridos (arabinosa y xilosa) fueron determinados con cromatógrafo de gases – espectrómetro de masa (GC/MS). El contenido de WEAX en harina de trigo integral y fracciones pulverizadas de variedades de trigo se situó entre 6,9 y 12,1 g/kg y entre 3,6 y 7,9 g/kg, respectivamente. WEAX tuvo un impacto negativo en la calidad de gluten, al observarse una reducción en la fortaleza del gluten. Además, la adición de arabinoxilano extraíble en agua a la preparación de pan mostró un aumento significativo en volumen y mejora de textura del producto final. El arabinoxilano extraíble en agua tiene potencial para ser extraído y utilizado en productos basados en cereales para una mejor calidad y adición de valor.

Arabinoxylans and Arabinogalactans: A Comprehensive Treatise

The functional and nutraceutical importance of various foods is often attributed to the bioactive molecules present in them. A number of components have been studied but dietary fiber and its different constituents are of prime consideration. Among these, arabinoxylan (AX) and arabinogalactan (AG) are of significant importance in that they hold potential in improving the quality of the baked products along with providing health benefits against various ailments. However, the improvements are dependent on their molecular weights, cross linkages, and solubility. Water-Extractable Arabinoxylan (WEAX) is more effective as compared to Water-Unextractable Arabinoxylan (WUEAX). In this review article, efforts were directed to describe the structural and molecular conformations of these functional ingredients. The discussion has been made regarding the functional properties of AX and AG, for example, improvements in water absorption capacities, dough stability time, and viscosity. They also improve the baking absorption of flour that is positively correlated with bread volume, the most important criterion for stakeholders. The arguments are also provided on the detrimental effects on gluten quality with some possible solutions. Their role in improving the quality and extending the shelf life of bread by reducing the process of staling and retrogradation is the main idea presented in the article. The nutraceutical perspectives were also highlighted as they are helpful in regulating blood cholesterol which thereby protect the body from cardiovascular disorders like atherosclerosis. Additionally, they act as prebiotics for microorganisms residing in the gastrointestinal tract.

Characterization of hemicellulosic fractions from spelt hull extracted by different methods

Arabinoxylans (AXs) from spelt hull were extracted by three different alkaline methods and by two methods with several modalities and two organic acids. The first method enabled to extract 1.4% of the water-extractable AXs (WE-AXs) of the hull with molecular weight (MW) of 5400 g/mol and arabinose to xylose (A/X) ratio of 0.55. The two successive extractions with 2% alkaline peroxide hydrogen at 60 °C during 4 h enabled to extract 20.4% of the water-unextractable AXs (WU-AXs) of the hull. Those fractions had MWs of 6800–7800 g/mol and 227 700–274 600 g/mol and A/X ratios of 0.32 and 0.45. The second method with 2% alkaline peroxide hydrogen at 50 °C during 24 h enabled to extract 25.4% of the hemicelluloses of the hull. The two AX populations had MW of 9200–11 400 g/mol and 256 800–273 200 g/mol with an A/X ratio of 0.36. The third method with NaOH gave the highest yield, 41.9% after a 16 h extraction. A/X ratios (0.18) and MWs (two populations of 9300–9500 g/mol) were lower than those of the previous methods. Organic acids method offered insufficient yields and compounds of very low MW (1300–11 300 g/mol). Methods with alkaline peroxide hydrogen enabled to obtain high MWs and high A/X ratios with moderate yields while the NaOH method gave the highest yield efficiency with lower MWs and A/X ratios. Organic acids method did not bring any advantage neither on the yield nor on the MWs of the compounds.

Relative contribution of wheat flour constituents to Solvent Retention Capacity profiles of European wheats

Solvent Retention Capacity (SRC) tests have originally been designed to predict flour functionality of North American wheat flours. A SRC profile consists of its Water Retention Capacity (WRC), Sodium Carbonate SRC (SCSRC), Sucrose SRC (SuSRC) and Lactic Acid SRC (LASRC) values. As the value of such tests when considering European wheat flours is rather unclear, we studied the chemical composition and SRC profiles of nineteen commercial European wheat flours. Their WRC, SCSRC, SuSRC and LASRC ranged from 56 to 66%, 74 to 88%, 90 to 102% and 106 to 147%, respectively. Both WRC and SCSRC were mostly higher than those of North American soft wheat flours, but in the range of those of North American hard wheat flours. For the entire set of European flours, strong linear relations were observed between the flour damaged starch levels and WRC values, as well as with SCSRC values. Modifying specific flour constituent properties and levels illustrated the contribution of proteins, damaged starch and arabinoxylan (AX) to the SRC values. Flour proteins, especially glutenins, mainly contributed to LASRC, while damaged starch largely impacted flour SCSRC. Water-extractable AX only contributed to the SuSRC values, whereas the solvent-accessible AX generally contributed to all SRC values, and particularly to the SuSRC values.