Technological and Analytical Methods for Arabinoxylan Quantification from Cereals

Cereal-Derived Water-Unextractable Arabinoxylans: Structure Feature, Effects on Baking Products and Human Health

Arabinoxylans (AXs) are non-starch polysaccharides with complex structures naturally occurring in grains (i.e., barley, corn, and others), providing many health benefits, especially as prebiotics. AXs can be classified as water-extractable (WEAX) and water-unextractable (WUAX) based on their solubility, with properties influenced by grain sources and extraction methods. Numerous studies show that AXs exert an important health impact, including glucose and lipid metabolism regulation and immune system enhancement, which is induced by the interactions between AXs and the gut microbiota. Recent research underscores the dependence of AX physiological effects on structure, advocating for a deeper understanding of structure-activity relationships. While systematic studies on WEAX are prevalent, knowledge gaps persist regarding WUAX, despite its higher grain abundance. Thus, this review reports recent data on WUAX structural properties (chemical structure, branching, and MW) in cereals under different treatments. It discusses WUAX applications in baking and the benefits deriving from gut fermentation.

Sugarcane Straw as a Source of Arabinoxylans: Optimization and Economic Viability of a Two-Step Alkaline Extraction

Sugarcane processing produces a significant amount of byproducts in the form of straw and bagasse, which are rich in cellulose, hemicellulose, and lignin. This work aims to provide a valorization approach to sugarcane straw by optimizing a two-step alkaline extraction of arabinoxylans by a response surface methodology to evaluate a potential industrial-scale production. Sugarcane straws were delignified using an alkaline-sulfite pretreatment, followed by alkaline extraction and precipitation of arabinoxylan, a two-step process optimized using a response surface methodology. A KOH concentration of (2.93-17.1%) and temperature (18.8-61.2 °C) were chosen as independent variables, and the arabinoxylan yield (%) as a response variable. The model application shows that KOH concentration, temperature, and the interaction between both independent variables are significant in extracting arabinoxylans from straw. The best-performing condition was further characterized by FTIR, DSC, and chemical and molecular weight evaluation. The straws arabinoxylans presented high purities levels, ca. 69.93%, and an average molecular weight of 231 kDa. The overall estimated production cost of arabinoxylan from straw was 0.239 €/g arabinoxylan. This work demonstrates a two-step alkaline extraction of the arabinoxylans method, as well as their chemical characterization and economic viability analysis, that can be used as a model for industrial scale-up production.

The Wheat Aleurone Layer: Optimisation of Its Benefits and Application to Bakery Products

The wheat aleurone layer is, according to millers, the main bran fraction. It is a source of nutritionally valuable compounds, such as dietary fibres, proteins, minerals and vitamins, that may exhibit health benefits. Despite these advantages, the aleurone layer is scarce on the market, probably due to issues related to its extraction. Many processes exist with some patents, but a choice must be made between the quality and quantity of the resulting product. Nonetheless, its potential has been studied mainly in bread and pasta. While the nutritional benefits of aleurone-rich flour addition to bread agree, opposite results have been obtained concerning its effects on end-product characteristics (namely loaf volume and sensory characteristics), thus ensuing different acceptability responses from consumers. However, the observed negative effects of aleurone-rich flour on bread dough could be reduced by subjecting it to pre- or post-extracting treatments meant to either reduce the particle size of the aleurone's fibres or to change the conformation of its components.

Metabolomics of Rice Bran Differentially Impacted by Fermentation With Six Probiotics Demonstrates Key Nutrient Changes for Enhancing Gut Health

The consumption of rice bran has been shown to have a positive effect on nutritional status and prevention of chronic diseases related to hundreds of metabolites with bioactivity. Consumption after fermentation can lead to specific beneficial effects, yet is lacking complete characterization when fermented with diverse strains. The objective of this study was to examine the effect of fermentation on the rice bran metabolite profile. Bacterial probiotics (Bifidobacterium longum, Limosilactobacillus fermentum, Lacticaseibacillus paracasei, Lacticaseibacillus rhamnosus and, Escherichia coli) were used to ferment rice bran alone or after incubation with yeast probiotic Saccharomyces boulardii. Fermented rice bran was methanol extracted and analyzed by UPLC-MS/MS. The metabolome of the two fermentation types was deeply modified when compared with non-fermented rice bran. The two-step fermentation provided alternative substrate to the bacteria in a few cases. Key metabolites of high nutritional value (essential amino acids, vitamins) and gut health (arabinose, maltotriose) were identified.

Isolation, Structural, Functional, and Bioactive Properties of Cereal Arabinoxylan─A Critical Review

Arabinoxylans (AXs) are widely distributed in various cereal grains, such as wheat, corn, rye, barley, rice, and oat. The AX molecule contains a linear (1,4)-β-D-xylp backbone substituted by α-L-araf units and occasionally t-xylp and t-glcpA through α-(1,2) and/or α-(1,3) glycosidic linkages. Arabinoxylan shows diversified functional and bioactive properties, influenced by their molecular mass, branching degree, ferulic acid (FA) content, and the substitution position and chain length of the side chains. This Review summarizes the extraction methods for various cereal sources, compares their structural features and functional/bioactive properties, and highlights the established structure-function/bioactivity relationships, intending to explore the potential functions of AXs and their industrial applications.

Rye: A wonder crop with industrially important macromolecules and health benefits

Rye (Secale cereale) is a rich source of macromolecules, especially starch, fiber, and proteins which encourages the researchers and industries to use it for various purposes including bakery products, beverages and edible films formulation. However, despite many nutritional and health benefiting properties, rye has not been explored up to its full potential. Interest of consumers in formulating foods with high fiber and phenolic compounds has generated our interest in compiling the detailed information on rye. The present review on rye grains summarizes the existing scientific data on rye macronutrients (starch, arabinoxylan, β-glucan, fructan and proteins) and their corresponding industrial importance. Detailed description in this review unfolds the potential of rye grains for human nutrition. This review provides comprehensive knowledge and fills the remaining gap between the previous and latest scientific findings. Comprehensive information on rye nutrients along with health benefits will help to open a new era for scientific world and industrial sectors.

Interactive effects of molecular weight and degree of substitution on biological activities of arabinoxylan and its hydrolysates from triticale bran

Arabinoxylan (AX) has many beneficial health effects that are closely related to its structural characteristics. The current study aimed to investigate the effects of molecular weight (Mw) and degree of substitution (DS) on the antioxidant and hypoglycemic activities of triticale bran AX and its hydrolysates in vitro. At low and similar Mw, the antioxidant activity of AX was inversely proportional to its DS. When DS was close, the antioxidant activity of AX was inversely proportional to its Mw at high DS, but the opposite result was found at low DS. As for the hypoglycemic performance, when DS was similar, the hypoglycemic activity of AX was proportional to its Mw. At low and similar Mw, the α-glucosidase inhibitory ability and glucose adsorption ability of AX was positively correlated with DS, whereas the α-amylase inhibitory ability and glucose delayed absorption ability showed the opposite results. Mw and DS had significant effects on the antioxidant and hypoglycemic activities of AX, and these two factors often need to be combined to explain the varied effects under different conditions.

Structural modifications to water-soluble wheat bran arabinoxylan through milling and extrusion

Feruloylated arabinoxylan (AX) is one of the most predominant dietary fiber in cereal grains. In recent decades, soluble AX has gained interest, as a result of its well-established health benefits. Apart from enzymatic degradation during cereal storage, food processing causes AX degradation. These reactions lead to structural modifications and influence both the AX functionalities and its health promoting effects. The aim of this study was to investigate the structural modifications and related property changes of health promoting water-extractable (WE) wheat bran AX through grain milling and extrusion. Multi-detector HPSEC revealed a correlation between M_w, conformational changes and the related viscosity behaviour depending on the processing type. Processing caused molecular degradation of insoluble high M_w AX, which increased the solubility significantly. Moreover, extrusion leaded to a more heterogenic AX fine structure. The detailed characterization of processed dietary fiber may help to facilitate the optimized incorporation of AX in health-promoting foods.

Water-Extractable Arabinoxylan-Induced Changes in the Conformation and Polymerization Behavior of Gluten upon Thermal Treatment

Interactions between gluten proteins and water-extractable arabinoxylan (WEAX) during the heating stage are crucial for the organoleptic quality of high-fiber cereal products. To reveal the molecular mechanism of WEAX on gluten characteristic upon heating, the current study comparatively investigated the effects of WEAX with different molecular weights (M_w) on the heat-evoked conformational variation and polymerization behavior of gluten. Results showed that WEAX, especially low M_w WEAX (L-WEAX), facilitated the polymerization ability of α-/γ-gliadins into glutenins, whereas high M_w WEAX (H-WEAX) reduced the polymerizing temperature of glutenin and gliadin. L-WEAX could develop more hydrogen bonds with tyrosine of gluten and stabilize the secondary structure more evidently than H-WEAX upon heating. Compared with disulfide bridge formation, hydrophobic interactions were not the driving force involved in the heat-induced polymerization behavior affected by WEAX. WEAX evoked the reinforced glutenin network and heterogeneous distribution of gliadin, with a more uniform molecular surface developed for gluten.

Structure, Antioxidant, and Hypoglycemic Activities of Arabinoxylans Extracted by Multiple Methods from Triticale

Different methods of isolating arabinoxylans (AXs) from triticale were performed to investigate the extraction methods’ effects on the physiological functions of the AXs. Structural, antioxidant, and hypoglycemic activities were determined. The molecular weights (MWs) of enzyme- or water-extracted AXs were lower than those of alkali-extracted AXs. Opposite trends were shown by the arabinose–xylose ratio. Enzyme-extracted AXs exhibited higher glucose adsorption capacity and hydroxyl radical-scavenging efficiency than alkali-extracted AXs. The α-amylase inhibition ability, DPPH radical-scavenging capacity, and metal-chelating activity of alkali-extracted AXs were higher than those of enzyme-extracted AXs. Water-extracted AXs had the highest glucose dialysis retardation index. In conclusion, extraction methods can influence the physiological function of AXs through their structural features. AXs with higher MWs and esterified ferulic acid (FA) levels had higher antioxidant ability, whereas AXs with higher solubility and free FA level exhibited higher hypoglycemic activity.

Interactions between soluble dietary fibers and wheat gluten in dough studied by confocal laser scanning microscopy

Four soluble dietary fiber (SDF) fractions characterized by major components of AXs, relatively narrow molecular weight distribution, different substituted ratio, and structure-sensitive parameter (ρ) were prepared from wheat bran. The fractions were added to wheat dough to determine the interactions between the dough's network and the SDF fractions relative to their physicochemical characteristics. Furthermore, a comprehensive study focusing on the dough texture characteristic, tensile properties, thermodynamic stability, and the microstructure was conducted by performing texture profile analysis (TPA), differential scanning calorimetry (DSC), and confocal laser scanning microscopy (CLSM) experiments. Additionally, an estimation function of the interactions parameters between the dough's network and the SDF fractions related to the factor molecular weight and ρ of the SDFs was established. The results indicated that the SDF fractions exhibiting a medium molecular weight, and a higher substitution degree and di-substituted ratio, were the most suitable fortifier providing benefits to the dough's qualities. Furthermore, the research methodology might support the high potential of SDF fractions as fortifier for flour-based products.