Phenolic residues in spruce galactoglucomannans improve stabilization of oil-in-water emulsions

Hypothesis: Amphiphilic character of surfactants drives them at the interface of dispersed systems, such as emulsions. Hemicellulose-rich wood extracts contain assemblies (lignin-carbohydrate complexes, LCC) with natural amphiphilicity, which is expected to depend on their chemical composition resulting from the isolation method. Lignin-derived phenolic residues associated with hemicelluloses are hypothesized to contribute to emulsions' interfacial properties and stability. Experiments: We investigated the role of phenolic residues in spruce hemicellulose extracts in the stabilization of oil-in-water emulsions by physical and chemical approach. Distribution and changes occurring in the phenolic residues at the droplet interface and in the continuous phase were studied during an accelerated storage test. Meanwhile, the physical stability and lipid oxidation in emulsions were monitored. Findings: Naturally associated lignin residues in GGM act as vehicles for anchoring these hemicelluloses into the oil droplet interface and further enable superior stabilization of emulsions. By adjusting the isolation method of GGM regarding their phenolic profile, their functionalities, especially interfacial behavior, can be altered. Retaining the native interactions of GGM and phenolic residues is suggested for efficient physical stabilization and extended protection against lipid oxidation. The results can be widely applied as guidelines in tailoring natural or synthetic amphiphilic compounds for interfacial stabilization. (C) 2017 Elsevier Inc. All rights reserved.Peer reviewe

Films from Glyoxal-Crosslinked Spruce Galactoglucomannans Plasticized with Sorbitol

Films were prepared from a renewable and biodegradable forest biorefinery product, spruce O-acetyl-galactoglucomannans (GGMs), crosslinked with glyoxal. For the first time, cohesive and self-standing films were obtained from GGM without the addition of polyol plasticizer. In addition, glyoxal-crosslinked films were prepared using sorbitol at 10, 20, 30, and 40% (wt.-% of GGM). Glyoxal clearly strengthened the GGM matrix, as detected by tensile testing and dynamic mechanical analysis. The elongation at break of films slightly increased, and Young's modulus decreased with increasing sorbitol content. Interestingly, the tensile strength of films was constant with the increased plasticizer content. The effect of sorbitol on water sorption and water vapor permeability (WVP) depended on relative humidity (RH). At low RH, the addition of sorbitol significantly decreased the WVP of films. The glyoxal-crosslinked GGM films containing 20% sorbitol exhibited the lowest oxygen permeability (OP) and WVP of the studied films and showed satisfactory mechanical performance

The Hydrophobicity of Lignocellulosic Fiber Network Can Be Enhanced with Suberin Fatty Acids

Suberin fatty acids were extracted from outer bark of Silver birch (Betula pendula Roth.) using an isopropanolic sodium hydroxide solution. Laboratory sheets composed of lignocellulosic fiber networks were prepared from unbleached and unrefined softwood kraft pulp and further impregnated with suberin fatty acid monomers and cured with maleic anhydride in ethanol solution. The treatment resulted in hydrophobic surfaces, in which the contact angles remained over 120 degrees during the entire measurement. The fiber network also retained its water vapor permeability and enhanced fiber–fiber bonding resulted in improved tensile strength of the sheets. Scanning electron microscopy (SEM) images revealed that the curing agent, together with suberin fatty acids, was evenly distributed on the fiber surfaces and smoothing occurred over the wrinkled microfibrillar structure. High concentrations of the curing agent resulted in globular structures containing betulinol derivates as revealed with time-of-flight secondary ion mass spectrometry (ToF-SIMS). Also, the larger amount of suberin fatty acid monomers slightly impaired the optical properties of sheets

The Hydrophobicity of Lignocellulosic Fiber Network Can Be Enhanced with Suberin Fatty Acids

Suberin fatty acids were extracted from outer bark of Silver birch (Betula pendula Roth.) using an isopropanolic sodium hydroxide solution. Laboratory sheets composed of lignocellulosic fiber networks were prepared from unbleached and unrefined softwood kraft pulp and further impregnated with suberin fatty acid monomers and cured with maleic anhydride in ethanol solution. The treatment resulted in hydrophobic surfaces, in which the contact angles remained over 120 degrees during the entire measurement. The fiber network also retained its water vapor permeability and enhanced fiber–fiber bonding resulted in improved tensile strength of the sheets. Scanning electron microscopy (SEM) images revealed that the curing agent, together with suberin fatty acids, was evenly distributed on the fiber surfaces and smoothing occurred over the wrinkled microfibrillar structure. High concentrations of the curing agent resulted in globular structures containing betulinol derivates as revealed with time-of-flight secondary ion mass spectrometry (ToF-SIMS). Also, the larger amount of suberin fatty acid monomers slightly impaired the optical properties of sheets

Environmentally-compatible alkyd paints stabilized by wood hemicelluloses

Wood biorefining currently involves large-scale industrial processes where a notable portion of raw materials, namely hemicelluloses and lignin, are either lost with the process water, degraded, or burnt for energy. Value added utilization of polymeric hemicelluloses is challenging due to their intermediate molar mass and the presence of other wood components, such as phenolic residues or wood extractives. Oil-in-water (O/W) emulsions represent a diverse and abundant class of applications in which the natural properties of wood hemicelluloses are beneficial. In the current work, we present highly promising new technical alkyd paint emulsion systems stabilized with hardwood glucuronoxylans (GX) and softwood galactoglucomannans (GGM). Samples from three isolation methods and their further fractionation by ethanol precipitation were systematically compared with regard to hemicellulose composition, interfacial activity, and functionality in emulsions. Emulsification of alkyd resins was successful with both GX and GGM obtained by various biorefining strategies. The highest emulsion stability over storage was achieved using crude non-purified GX and GGM fractions, and was correlated with the presence of phenolic compounds and extractives, interfacial activity, and small droplet size. Hardwood GX and softwood GGM are envisioned as natural emulsifiers of alkyd O/W emulsions, which are examples of diverse and abundantly-used technical dispersions. This study can be utilized as a guideline for targeted extraction of hemicelluloses with desired functionality, and as a protocol for developing environmentally-compatible industrial dispersions.Peer reviewe