Optimization of Arabinoxylan Isolation from Rye Bran by Adapting Extraction Solvent and Use of Enzymes

Abstract

Physicochemical and functional properties of arabinoxylans (AXs) can be significantly influenced by their isolation method. Finding balanced process conditions that allow optimal extraction yields while preserving AXs functionality is a challenge. The aim of this study was to determine the effect of different chemical solvents with neutral and alkaline pH on the intrinsic properties and extraction yield of AXs isolated from rye bran. Additionally, the application of xylanases and other cell wall degrading enzymes (Pentopan Mono BG, Deltazym XL‐VR, Viscoflow BG) to solubilize bound AXs was investigated. Results show that the use of Ca(OH)2 for isolation was superior to water and Na2CO3, as it selectively solubilized AXs and delivered isolates with a purity of up to 43.92% AX and a moderate ferulic acid (FA) content (209.35 ± 16.79 mg FA/100 g AX). Application of xylanases was further able to duplicate these achieved AX yields (7.50 to 9.85g AX/100 g bran). Additionally, isolates displayed highest ferulic acid contents (445.18 to 616.71 mg FA/100 g AX) and lowest impurities in comparison to chemical extracted AXs. Rheological characterization of the isolates showed a pronounced shear thinning behavior which fitted well to the power‐law model (R 2 > 0.989). Differences in pseudoplasticity of the isolates suggested that structural and chemical properties might have been responsible for this behavior.

Effect of Differently Extracted Arabinoxylan on Gluten-Free Sourdough-Bread Properties

“…e composition of each concentrate varied significantly amongst arabinoxylans, and therefore, different functionalities in the GF batter were expected. Especially, FA might favor cross-linking to a different degree, but also other properties such as their branching degree (A/X ratio), molecular weight, and the presence of coextracted impurities (i.e., glucose and dextrins, protein, and other dietary fiber components) might determine their behavior in the bread batter as reported in earlier studies [3,8].…”

“…Previous research has already confirmed that extraction parameters (solvents, pH, or temperature) significantly modify the chemical and functional properties of AXs, which in turn affect the rheological behavior of gluten-free batters [8,9]. eir effect will closely depend not only on the type and concentration of AX added but also on the selection of GF flour and the presence of oxidants in the batter [3].…”

“…Arabinoxylans were extracted from rye bran by following the procedure of Bender et al [8] using a two-step extraction or a successive extraction as shown in Figure 1. For the solvent extraction, water, calcium hydroxide, and sodium carbonate were selected.…”

“…Ferulic acid of AXs was analyzed by following the procedure of Mattila et al [11]. For the determination of the AX content, monosaccharide composition was measured by gas chromatography with a precolumn derivatization as described by Bender et al [8].…”

Improving gluten-free buckwheat bread by sourdough fermentation and addition of arabinoxylan and pyranose 2-oxidase

“…These properties were derived from Bender et al (2018b), except for the starch content, which was calculated by differences. Rye AX was extracted with calcium hydroxide following the procedure of Bender et al (2017b) and POx was recombinantly expressed from the white rot fungus Phanerochaete chrysosporium and purified, as explained by Spadiut et al (2010). A commercial GF rice-based sourdough starter culture (Böcker Reinzucht-Sauerteig-Reis) was purchased from Ernst Böcker GmbH & Co (Minden, Germany).…”