Galactoglucomannans (GGM) and glucoronoxylans (GX) are the most abundant hemicelluloses in softwood and hardwood, respectively. Recently, GGM- and GX-rich assemblies obtained through pressurized hot water flow-through extraction (PHWE) of wood saw meal proved to be more efficient emulsifiers than conventional food hydrocolloids, and they also protected emulsified lipids against oxidation. Our hypothesis is that hemicelluloses and phenolic residues in the extracts are covalently linked forming lignin-carbohydrate complexes (LCC). The presence of LCC in the GGM- and GX-rich assemblies likely enhances their functionality in colloidal systems. To confirm this hypothesis, the presence of LCC in GGM- and GX-rich assemblies was investigated. Firstly, GGM and GX was recovered from spruce and birch by PHWE, respectively, and spray-dried (s-).The chemical structure of the samples was investigated in detail by specialized techniques including high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD), size-exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) spectroscopy. Then, further physical fractionation was performed using ultracentrifugation and nanofiltration and samples were assessed regarding to the presence of LCC bonds. The presence of phenylglycoside and γ-ester LCC bonds was confirmed in all fractions recovered from sGGM and sGX. The presence of various contours in the phenylglycoside-region indicated that various polysaccharides bind to lignin through this LCC bond type. Benzylether structure were enriched by physical fractionation in sGGM and sGX fractions containing larger molecules (&gt;500 Da) insoluble in water. Overall findings suggested that GGM- and GX-rich extracts are functionalized by the presence of LCCs, which may contribute to their excellent emulsion stabilization capacity.

Analytical insights on lignin-carbohydrate complexes in softwood and hardwood extracts

ACS Spring Meeting 2021

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