Water-unextractable Arabinoxylan Research Articles

Effects of xylanase on starch isolation and functional properties of waxy wheat flour

Waxy wheat starch is difficult to be extracted from waxy wheat flour (WWF) due to the weak gluten quality and the existence of arabinoxylan (AX). The objective of this study was to understand effects of xylanase on starch isolation and functional properties of WWF. WWF with addition of xylanase had a lower water retention capacity, shorter dough development time, and longer dough stability time when compared to the one without xylanase. Addition of xylanase to the WWF dough decreased its viscoelasticity and bound water, increased its extensibility and immobilized water, and transformed it from the elastic to the extensible texture. The xylanase hydrolysis of water-unextractable AX promoted quick formation of gluten and the release of starch granules during wet milling of WWF. Results suggested that WWF could be wet-milled without any challenge by adding xylanase. A role of AX in the dough and during wet milling of WWF was proposed and illustrated.

Unraveling the deterioration mechanism of dough during whole wheat flour processing: A case study of gluten protein containing arabinoxylan with different molecular weights

This study aims to the effect of arabinoxylan (AX) on gluten quality. Ultrasonic treatment is utilized to degrade water unextractable arabinoxylans (WUAX) from wheat bran, which obtains three molecular weights of AX. The results indicate that the shear viscosity and particle size of AX were decreased and the ζ-potential was increased after ultrasonic treatment. Analysis of the gluten shows that the free SH of gluten with 6% WUAX, SAX10, and SAX30 (ultrasound duration for 10 min and 30 min) was increased by 51.9%, 48.1%, and 17.0%, respectively, whereas the free SH of 2% SAX30-gluten was increased by 19.8%. Furthermore, WUAX impaired the viscoelasticity properties of gluten, while SAX30 improved the viscoelasticity of gluten. WUAX induced the open, fragile, and discontinuous structure of gluten. On the contrary, SAX30 promoted the formation of the compact and regular gluten structure. Overall, ultrasonic as a non-chemical treatment could be used to improve the quality of whole-wheat foods.

Entanglement between Water Un-Extractable Arabinoxylan and Gliadin or Glutenins Induced a More Fragile and Soft Gluten Network Structure.

This study aimed to investigate the effects of water-unextractable arabinoxylan (WUAX) on the gluten network structure, especially on gliadins and glutenins. The results indicated that the free sulfhydryl (free SH) of gliadins increased by 25.5% with 100 g/kg WUAX, whereas that of glutenins increased by 65.2%, which inhibited the formation of covalent bonds. Furthermore, β-sheets content decreased 5.63% and 4.75% for gliadins and glutenins with 100 g/kg WUAX, respectively, compared with the control. WUAX increased β-turns prevalence for gliadins, while the content of α-helixes and random coils had less fluctuation. In glutenins, the contents of α-helixes and β-sheets decreased and β-turns increased. Moreover, compared with the control, the weight loss rate for gliadins and glutenins increased by 2.49% and 2.04%, respectively, with 60 g/kg WUAX. The dynamic rheological analysis manifested that WUAX impaired the viscoelasticity property of gliadin and glutenin. Overall, WUAX weakened the structure of the gliadins and glutenins, leading to quality deterioration of gluten.

Determining levels of water-extractable and water-unextractable arabinoxylan in commercial Swedish wheat flours by a high-throughput method

A high-throughput method for quantification of water extractable arabinoxylan (WE-AX) and water unextractable arabinoxylan (WU-AX) was adapted for and evaluated on 197 commercial Swedish wheat flours, collected continuously during harvest years 2018 and 2019. In the method, starch was hydrolysed by alpha-amylase and WE-AX was precipitated with 80% ethanol. AX residues were quantified by gas chromatography after acid hydrolysis. The method had a good repeatability (2.1% RSDr for total AX). Spring wheat flour had a higher WE-AX content (0.68%) and lower WU-AX content (1.19%) than winter wheat flour (0.56% and 1.31%). The variation of total AX content was high for winter wheat flour (1.5–2.2%), with no correlation to ash or protein content. Total AX content differed significantly both between harvest years and locations, indicating an impact from environment on AX composition. Overall, the method enabled high-throughput analysis of wheat flour and can be further used to study how endogenous AX impacts baking quality.

Characterization and application of a novel xylanase from Halolactibacillus miurensis in wholewheat bread making.

The presence of arabinoxylan in wholewheat flour affects its quality significantly. Here, an efficient arabinoxylan hydrolytic enzyme, Hmxyn, from Halolactibacillus miurensis was identified and heterologously expressed in pichia pastoris. Moreover, its relevant properties, including potential application in the wholewheat bread were evaluated. Recombinant Hmxyn exhibited maximal activity at 45°C and pH 6.5, and was stable at mid-range temperature (<55°C) and pH (5.5–8.0) conditions. Hmxyn had a clear hydrolysis effect on wheat arabinoxylan in dough and caused the degradation of the water-unextractable arabinoxylan, which increased the content of wheat soluble arabinoxylan of dough. The fermentation characteristics results and microstructure analysis revealed that Hmxyn improved the organizational structure and air holding capacity of fermented dough, thus promoting the dough expansion. Baking experiments further showed that Hmxyn significantly increased specific volume- and texture-linked properties of wholewheat breads. This study indicates the application potential of Hmxyn in the preparation of wholewheat bread.

Hydration of Wheat Flour Water-Unextractable Cell Wall Material Enables Structural Analysis of Its Arabinoxylan by High-Resolution Solid-State 13C MAS NMR Spectroscopy.

To enable its structural characterization by nuclear magnetic resonance (NMR) spectroscopy, the native structure of cereal water-unextractable arabinoxylan (WU-AX) is typically disrupted by alkali or enzymatic treatments. Here, WU-AX in the wheat flour unextractable cell wall material (UCWM) containing 40.9% ± 1.5 arabinoxylan with an arabinose-to-xylose ratio of 0.62 ± 0.04 was characterized by high-resolution solid-state NMR without disrupting its native structure. Hydration of the UCWM (1.7 mg H2O/mg UCWM) in combination with specific optimizations in the NMR methodology enabled analysis by solid-state 13C NMR with magic angle spinning and 1H high-power decoupling (13C HPDEC MAS NMR) which provided sufficiently high resolution to allow for carbon atom assignments. Spectral resonances of C-1 from arabinose and xylose residues of WU-AX were here assigned to the solid state. The proportions of un-, mono-, and di-substituted xyloses were 59.2, 19.5, and 21.2%, respectively. 13C HPDEC MAS NMR showed the presence of solid-state fractions with different mobilities in the UCWM. This study presents the first solid-state NMR spectrum of wheat WU-AX with sufficient resolution to enable assignment without prior WU-AX solubilization.

The Influence of Water-Unextractable Arabinoxylan and Its Hydrolysates on the Aggregation and Structure of Gluten Proteins.

This study aimed to investigate the influence of water-unextractable arabinoxylan (WUAX) and its hydrolysates on the aggregation and structure of gluten proteins and reveal the underlying mechanism. In this work, the WUAX was treated with enzymatic hydrolysis and the changes of their molecular weights and structures were analyzed. Meanwhile, the conformation and aggregation of gluten were determined by reversed-phase HPLC, FT-Raman spectroscopy, and confocal laser scanning microscopy. The results showed that the extra WUAX could impair the formation of high Mw glutenin subunits, and the enzymatic hydrolysis arabinoxylan (EAX) could induce the aggregation of gluten subunits. And, the gluten microstructure was destroyed by WUAX and improved by EAX. Besides, the interactions of WUAX and EAX with gluten molecules were different. In summary, these results indicated that enzymatic hydrolysis changed the physicochemical properties of arabinoxylan and affected the interaction between arabinoxylan and gluten proteins.

Investigation the influences of water-extractable and water-unextractable arabinoxylan on the quality of whole wheat you-tiao and its mechanism

This research aimed to investigate the effects of water-extractable arabinoxylan (WEAX) and water-unextractable arabinoxylan (WUAX) on the quality of you-tiao. In this work, the interactions between different amounts of AX and wheat gluten were extensively evaluated during frying treatment. The results showed that WEAX impaired the surface hydrophobicity of gluten and improved its solubility, while WUAX had the opposite effect. The fluorescence spectra revealed that WEAX and WUAX changed the conformation of gluten molecules. Besides, chemical interaction measurement indicated that WEAX and WUAX prevented the formation of partial disulfide bonds and inhibited the thermal aggregation of gluten proteins. In summary, the results indicated that WEAX partly improved the properties of you-tiao. Meanwhile, WUAX reduced the dough's oil content and specific volume, resulting in you-tiao with poor quality.

The Effect of Arabinoxylan and Wheat Bran Incorporation on Dough Rheology and Thermal Processing of Rotary-Moulded Biscuits.

Wheat bran incorporation into biscuits may increase their nutritional value, however, it may affect dough rheology and baking performance, due to the effect of bran particles on dough structure and an increase in water absorption. This study analyzed the enrichment effect of wheat bran and arabinoxylans, the most important non-starch polysaccharides found in whole wheat flour, on dough rheology and thermal behaviour during processing of rotary-moulded biscuits. The objective was to understand the contribution of arabinoxylans during biscuit-making and their impact when incorporated as wheat bran. Refined flour was replaced at 25, 50, 75, or 100% by whole flour with different bran particle sizes (fine: 4% > 500 μm; coarse: 72% > 500 μm). The isolated effect of arabinoxylans was examined by preparing model flours, where refined flour was enriched with water-extractable and water-unextractable arabinoxylans. Wheat bran had the greatest impact on dough firmness and arabinoxylans had the greatest impact on the elastic response. The degree of starch gelatinization increased from 24 to 36% in biscuits enriched with arabinoxylans or whole flour and coarse bran. The microstructural analysis (SEM, micro-CT) suggested that fibre micropores may retain water inside their capillaries which can be released in a controlled manner during baking.

Improving rye bread antioxidant capacity by bread-making methodology: Contribution of phosphate-buffered saline- and methanol-soluble phenolic phytochemicals with different molecular profiles

Bread antioxidant properties may be considerably modified in the bread-making process. To indicate the bread-making methods that may boost its antioxidant properties, five bread types were produced by straight dough and sourdough methods from seven rye cultivars. Their antioxidant, chemical and molecular characteristics were investigated in PBS and MeOH extracts. Free and conjugated phenolic acids (esters and glucosides) predominated in both extracts. Nevertheless, PBS-soluble fractions also comprised feruloylated arabinoxylans (69–83 μg/g and 28–29 mg/g of bread, for ferulic acid and arabinoxylan, respectively) with high molar masses (443000–556000 g/mol). They showed markedly higher concentration of Folin-Ciocalteu reactive components and two times higher ABTS•+ scavenging capacity than MeOH-soluble ones. These parameters were significantly correlated with bread acidity and arabinoxylan-esterified ferulic acid content. Consequently, rye bread with the lowest pH, obtained by a straight method with lactic acid addition, exhibited substantially increased antioxidant capacity, owing to the most efficient hydrolysis of highly feruloylated water-unextractable arabinoxylans during bread-making. This study showed that macromolecule-bound ferulic acid present in physiologically relevant PBS extract of rye bread is a stronger antioxidant than much more abundant low molar mass phenolics extracted with MeOH. Thus, PBS extract might better reflect antioxidant potency of cereal-based products.

Interactions between gluten and water-unextractable arabinoxylan during the thermal treatment

This study aimed to investigate the interactions between gluten and water-unextractable arabinoxylan (WUAX), which changed the conformation and aggregation of gluten during the thermal treatment. In this work, the interactions between water-unextractable arabinoxylan and wheat gluten during thermal treatment were extensively evaluated by different techniques. The results showed that the extra WUAX could impair the viscoelasticity as well as weaken the thermal properties of gluten. The fluorescence spectra revealed the extra WUAX changed the conformation of gluten molecules. Besides, chemical interaction measurement indicated that the extra WUAX prevented the formation of partial disulfide bonds and had a major effect on the hydrophobic interaction of gluten. In summary, these results indicated that WUAX disrupted the covalent crosslinking by affecting disulfide bonds between gluten proteins, and dominated the folding/unfolding process of gluten via the competition with gluten for water, resulting in the poor quality of whole wheat-based foods.

Assessing the impact of xylanase activity on the water distribution in wheat dough: A 1H NMR study

The molecular mobility of water and biopolymers in wheat dough and the influence of xylanases thereon was investigated with time domain proton nuclear magnetic resonance relaxometry. To reduce the complexity, model systems containing starch, gluten and/or water-unextractable arabinoxylan (WU-AX) were used. In the starch-WU-AX-water model, starch binds water fast but less strong compared to WU-AX, resulting in water withdrawal from starch during resting. In contrary, WU-AX did not affect the water distribution in a gluten-WU-AX-water system, despite the higher water retention capacity (WRC) of WU-AX compared to gluten. In a starch-gluten-WU-AX-water model and in wheat flour, water was distributed over the different constituents including WU-AX. Addition of xylanase reduced the WRC of WU-AX, resulting in a release of water. Therefore, the beneficial effect of xylanase on dough and bread quality can, in part, be attributed to the redistribution of water, initially bound by WU-AX, between the other flour constituents.

Phenolic Acids, Antioxidant Capacity, and Estimated Glycemic Index of Cookies Added with Brewer's Spent Grain.

Brewers' spent grain (BSG) is the major by-product of the brewing industry, with great potential as a functional ingredient due to its bioactive compounds. Thus, BSG could be suitable for improving the low nutritional quality of wheat-based snacks highly consumed by young people. The objective of this study was to substitute wheat flour with BSG (0, 10, 20, and 30%) for cookies elaboration, and evaluate the dough rheology, phenolic acids, antioxidant capacity, arabinoxylans content and proximate composition of the cookies Protein content and bioactive compounds (ferulic and p-coumaric acids, water unextractable arabinoxylans) of cookies significantly (p < 0.05) increased with the substitution level. In comparison to the wheat-alone cookies, the 20% BSG-containing cookies showed a lower hydrolysis and glycemic index (GI), and less total starch. The low cost, protein-rich BSG with antioxidant capacity improves the nutritional quality of cookies and may confer health benefits beyond basic nutrition.

Age-related arabinoxylan hydrolysis and fermentation in the gastrointestinal tract of broilers fed wheat-based diets

Endoxylanases are frequently used in cereal-based broiler feeds to improve the nutritional quality of the feed. It is hypothesized that the age of broilers and the age-related development of their intestinal microbiota influence the efficacy of these enzymes. Hence, the objective of this study was to identify possible age-related changes in arabinoxylan (AX) digestion in the different parts of the gastrointestinal (GI) tract of broilers. A feeding trial was performed with 240 1-day-old chicks (Ross 308) receiving a wheat-based feed containing no supplemented endoxylanase. Digesta samples from every section of the GI tract were collected at 5, 10, 15, 21, 28, and 35d of age and analyzed for AX content, AX digestibility, intestinal viscosity, and microbial endoxylanase and arabinofuranosidase activities. In the first 2 wk, the microbiota were able to solubilize a part of the water-unextractable arabinoxylan (WU-AX), thereby increasing intestinal viscosity and water-extractable arabinoxylan (WE-AX) concentrations in the GI tract. In these young birds, WU-AX and WE-AX with low arabinose to xylose ratios were able to enter the caeca but were not yet extensively fermented by the caecal microbiota as indicated by the high caecal AX concentrations at 5 and 10d (P < 0.01). Establishment of a more mature microbial community at 3 wk of age resulted in a further increase in both the solubilization of WU-AX and fermentation of WE-AX at the ileum and caecum (P < 0.10). Furthermore, the increase in AX degrading enzyme activities with age denotes the high AX degrading capacity of the caecal microbiota. Finally, a total tract AX digestion of 24% was achieved at slaughter age (day 35). Our results clearly indicate that the capacity of intestinal microbiota to degrade AX in the hindgut increases as the broiler ages. This suggests that the benefits of endoxylanase supplementation of broiler feeds depend on the interaction of the intestinal microbiota and AX present in the GI tract at specific broiler ages.

Optimization of ultrasonic-microwave assisted alkali extraction of arabinoxylan from the corn bran using response surface methodology.

In this study, Ultrasonic-Microwave assisted alkali (UMAA) was applied to extract water-unextractable arabinoxylan (WUAX) from the corn bran. The various factors including ultrasonic power, concentration of sodium hydroxide, solvent-to-material ratio and ultrasonic-microwave synergetic time were optimized by response surface methodology coupled with Box-Behnken design (BBD) on basis of the results of single factor experiments. The results showed that the maximum WUAX yield of 27.78 ± 0.17% was obtained with ultrasonic power 500 W, concentration of sodium hydroxide 0.30 mol/L, solvent-to-material ratio 30 mL/g, ultrasonic-microwave synergetic time 25 min. FT-IR analysis processed the characteristic peaks of polysaccharide. Chemical composition analysis indicted WUAX was mainly composed of xylose, arabinose, glucose, galactose, rhamnose, mannose, glucuronic acid and galacturonic acid, at a ratio of 38.3:28.2:22.3:5.1:2.5:0.7:1.5:1.4, respectively. In addition, the antioxidant activity assay in vitro showed that WUAX processed strong Fe2+ chelating activity and good scavenging effect on DPPH radical. These results clearly indicated the UMAA is an effective method for extraction of antioxidant WUAX from corn bran and the polysaccharides could be exhibited broad development and application prospects.

Effects of pentosanase and glucose oxidase on the composition, rheology and microstructure of whole wheat dough

In the present study, the effects of pentosanase (Pn) and glucose oxidase (GOX) on the properties of whole wheat steamed buns dough were investigated, including the composition, rheology, and microstructure, to reveal the effects and mechanisms of action of these two enzymes in whole wheat steamed buns making. Compared with the Control, the dough exhibited a higher content of water extractable arabinoxylan and a stronger solubility in protein in the presence of Pn. Additionally, Pn-treated dough showed high extensibility, with the gluten matrix more open and the starch granules more visible. On the other hand, the addition of GOX decreased the number of free sulfhydryls and increased the content of glutenin macropolymer (GMP), indicating the formation of disulfide bonds. Reducing SDS-PAGE of albumin and globulin suggested the generation of large protein aggregates and the conjugation of protein-polysaccharide by non-disulfide covalent bonds. The GOX-treated dough was significantly strengthened, which generated a more continuous and highly dense gluten network. Although the effects of Pn and GOX on the dough were considerably different, they both significantly changed the rheology and microstructure of the dough, due to the solubilization of water un-extractable arabinoxylan and the increase of GMP and the formation of protein-polysaccharide conjugates. These effects observed for steamed buns could be extended to other fermented flour products.

Improving the physicochemical properties of whole wheat model dough by modifying the water-unextractable solids

Most studies on improving the quality of wheat flour products have been based on eliminating the adverse effects of water-unextractable arabinoxylan (WUAX) using pentosanase (Pn), but the interactions between the arabinoxylan released from WUAX and gluten have rarely been studied. The results demonstrated that Pn decreased the molecular weight of soluble AX released from water-unextractable solids (57,120–18,450 g mol−1). The released AX increased the amount of glutenin macropolymer, accompanied by a decrease in glutenin solubility, but made it more difficult for the free sulfhydryl to form disulfide bonds between glutenin proteins. This might be beneficial to the formation of uniform and fine crumb structures, and produced whole wheat Chinese steamed bread (CSB) with higher volume and lower firmness. However, the gluten network became more open and easier to fracture at higher level of Pn, which made it different to the further improvement in the texture of CSB.

Effects of water‐unextractable arabinoxylans on the physicochemical and rheological properties of traditional Chinese youtiao

AbstractThe effects of water‐unextractable arabinoxylans (WUAX) on the physicochemical properties of the dough and the final qualities of traditional Chinese youtiao were investigated. The farinographic properties of youtiao dough were slightly affected by extra WUAX, except that the water absorption increased from 56.77% to 64.93%. The extensographic properties varied complexly at different proofing time. The SEM micrographs of dough showed that the uniform starch granule structure could not be formed in youtiao dough with 4% extra WUAX. The specific volume of youtiao with 4% WUAX was only 3.68 cm3 g−1, which was 27.45% lower than that of control. The moisture content increased from 27.17% to 31.74%, and the hardness was almost four times higher than that of control. Most importantly, the total oil content of youtiao with 4% WUAX was only 12.29%, which was 37.31% lesser than the control. These results suggest that WUAX can be used in youtiao production to provide a low‐fat option with improved nutrition.

Phenolic compounds and antioxidant properties of arabinoxylan hydrolysates from defatted rice bran.

The water unextractable arabinoxylans (WUAX) contain beneficial phenolic compounds that can be used for food rather than for animal feed. The antioxidant activities of defatted rice bran obtained by xylanase-aided extraction is reported herein. The chemical and molecular characteristics of extracted fractions were investigated. The WUAX hydrolysate precipitated by 0-60% ethanol (F60), 60-90% ethanol (F6090), and more than 90% ethanol (F90) had decreased molar masses with increasing ethanol concentration. The fractions of interest, F60 and F6090, contained 75% arabinoxylans with ferulic acid as the major bound phenolic acid, followed by p-coumaric acid. According to chemical-based antioxidant assays F60 and F6090 exhibited higher diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and ferric iron reducing ability than F90 which contained minor contents of small sugars and free phenolic acids. In cell-based antioxidant assays, using the fluorescent 2',7'-dichlorofluorescein diacetate probe, all three fractions were potent intracellular scavengers. The high molar mass of WUAX hydrolysates with high amount of bound phenolics contributes to the chemical-based antioxidant activity. All fractions of WUAX hydrolysates showed high potent intracellular scavenging activity regardless of molar mass, content and the component of bound phenolics. © 2017 Society of Chemical Industry.

Fractionation-reconstitution studies to determine the functional properties of rye flour constituents

Rye flour was fractionated into starch, protein, water-extractable (WE), and water-unextractable (WU) arabinoxylans (AX). For protein isolation a novel method was developed consisting of extraction of rye flour at pH 9.5 and 50 °C followed by dialysis under slightly acidic conditions. Flours containing different amounts of these fractions were recombined; doughs were mixed and analyzed for their rheological behavior in order to get insight into the role of the different fractions on the dough properties. WEAX decreased the elastic properties of the doughs compared to the control dough, whereas WUAX led to an increase. In doughs containing both AX fractions the effects compensated each other. The onset of starch gelatinization in the reconstituted doughs and the difference to the temperature of complete gelatinization was strongly affected by the composition of the doughs. However, the role of the protein fraction on the elastic properties of the dough and on starch gelatinization remained unclear.