Wood hemicelluloses as effective wall materials for spray-dried microcapsulation of polyunsaturated fatty acid-rich oils

The most commonly-used and effective wall materials (WMs) for spray-dried microencapsulation of bioactive compounds are either costly, or derived from unsustainable sources, which lead to an increasing demand for alternatives derived from sustainable and natural sources, with low calories and low cost. Wood hemicelluloses obtained from by-products of forest industries appear to be attractive alternatives as they have been reported to have good emulsifying properties, low viscosity at high concentrations, high heat stability and low heat transfer. Here, we investigated the applicability of spruce galactoglucomannans (GGM) and birch glucuronoxylans (GX), to encapsulate flaxseed oil (FO, polyunsaturated fatty acid-rich plant based oil) by spray drying; and the results were compared to those of the highly effective WM, gum Arabic (GA). It was found that depending on solid ratios of WM:FO (1:1, 3:1 and 5:1), encapsulation efficiency of GGM was 88–96%, and GX was 63–98%. At the same encapsulation ratio, both GGM and GX had higher encapsulation efficiency than GA (49–92%) due to their ability to produce feed emulsions with a smaller oil droplet size and higher physical stability. In addition, the presence of phenolic residues in GGM and GX powders enabled them to have a greater ability to protect oil from oxidation during spray drying than GA. Physiochemical properties of encapsulated powders including thermal properties, morphology, molecular structure, particle size and water adsorption intake are also investigated. The study has explored a new value-added proposition for wood hemicelluloses which can be used as effective WMs in the production of microcapsules of polyunsaturated fatty acid-rich oils for healthy and functional products in food, pharmaceutical and cosmetic industries.Peer reviewe

Wood hemicelluloses as effective wall materials for spray-dried microcapsulation of polyunsaturated fatty acid-rich oils

The most commonly-used and effective wall materials (WMs) for spray-dried microencapsulation of bioactive compounds are either costly, or derived from unsustainable sources, which lead to an increasing demand for alternatives derived from sustainable and natural sources, with low calories and low cost. Wood hemicelluloses obtained from by-products of forest industries appear to be attractive alternatives as they have been reported to have good emulsifying properties, low viscosity at high concentrations, high heat stability and low heat transfer. Here, we investigated the applicability of spruce galactoglucomannans (GGM) and birch glucuronoxylans (GX), to encapsulate flaxseed oil (FO, polyunsaturated fatty acid-rich plant based oil) by spray drying; and the results were compared to those of the highly effective WM, gum Arabic (GA). It was found that depending on solid ratios of WM:FO (1:1, 3:1 and 5:1), encapsulation efficiency of GGM was 88–96%, and GX was 63–98%. At the same encapsulation ratio, both GGM and GX had higher encapsulation efficiency than GA (49–92%) due to their ability to produce feed emulsions with a smaller oil droplet size and higher physical stability. In addition, the presence of phenolic residues in GGM and GX powders enabled them to have a greater ability to protect oil from oxidation during spray drying than GA. Physiochemical properties of encapsulated powders including thermal properties, morphology, molecular structure, particle size and water adsorption intake are also investigated. The study has explored a new value-added proposition for wood hemicelluloses which can be used as effective WMs in the production of microcapsules of polyunsaturated fatty acid-rich oils for healthy and functional products in food, pharmaceutical and cosmetic industries.Peer reviewe

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

Functionality of spruce galactoglucomannans in oil-in-water emulsions

For a sustainable food chain, the demand for plant-based, functional, and cost-effective food hydrocolloids is on a high-rise. Hemicelluloses from the renewable lignocellulosic biomass are available in abundance from side-streams of the forestry industry to fulfill this demand. Their effective valorization requires a safe, economic extraction method that can be up-scaled to an industrial scale and, simultaneously, understanding of their functionality to develop applications. In this study, an aqueous-based extraction method, pressurized hot water extraction (PHWE) of spruce saw meal was used to obtain galactoglucomannans (GGM), "spruce gum". Ethanol precipitation was performed to remove non-polysaccharide extractives such as free phenolic compounds, and the emulsion component ratio-dependent interfacial saturation capacity of the remaining purified fraction was studied to understand its functionality. GGM resulted in good to excellent emulsification and stabilization of oil-in-water emulsions and exhibited adsorption at the oil droplet interface, which depended on the amount of oil and droplet size of emulsions. The adsorbed GGM content was determined by gas chromatography after acid methanolysis, and their macromolecular characteristics were studied by size-exclusion chromatography. At GGM to oil ratios 2, 1, and 0.4, stable emulsions with predicted several months of shelf life at room temperature were achieved. The results indicated mechanisms affecting the physical stabilization and breakdown of emulsions containing spruce gum, a novel sustainable hydrocolloid. (C) 2018 Elsevier Ltd. All rights reserved.Peer reviewe

Centrifugal fractionation of softwood extracts improves the biorefinery workflow and yields functional emulsifiers

With the emerging bio-based technologies, the fractionation of complex biomass is essential to obtain value-added functional molecules for material, chemical, and energy production. The refining process of biomasses often requires the use of solvents and hazardous chemicals, whose removal after fractionation decreases the eco-compatibility of the process and increases the cost and time of the refinement. Softwood extracts obtained through the environmentally friendly pressurized hot water extraction are heterogeneous mixtures rich in hemicelluloses and lignin. Here we developed a simple, fast, organic solvent-free, and sustainable method to fractionate softwood extracts using centrifugal forces. The characteristics of each obtained fraction in terms of composition, macromolecular properties (particle size, molar mass, charge), interfacial activity, and stabilization capacity were highly dependent on the centrifugal force and time applied. The hemicellulose and lignin contents in the fractions were balanced by centrifugal forces to obtain functional emulsifiers that efficiently stabilized the oil/water interface. Through fractionation of softwood extracts, we also found that both the hemicelluloses and lignin particles are involved in emulsion interface formation and stabilization. Centrifugation is a scalable concept that can be feasibly and easily introduced into the biorefinery system and used to optimize the composition of biomass fractions for targeted purposes.Peer reviewe

Sensory profile of spruce galactoglucomannans and birch glucuronoxylans in food

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Revealing the role of phenolic residues co-extracted with hemicelluloses as emulsion stabilizers

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Gel characteristics of low-acetyl spruce galactoglucomannans

Galactoglucomannans (GGM) recovered from abundant forest industry side-streams has been widely recognized as a renewable hydrocolloid. The low molar mass and presence of O-acetyl side-groups results in low viscous dispersions and weak intermolecular interactions that make GGM unsuitable for hydrogel formation, unless forcefully chemically derivatized and/or crosslinked with other polymers. Here we present the characterization of hydrogels prepared from GGM after tailoring the degree of acetylation by alkaline treatment during its recovery. Specifically, we investigated gel characteristics of low-acetyl GGM dispersions prepared at varied solid concentrations (5, 10 and 15 %) and pH (4, 7 and 10), and then subjected to ultrasonication. The results indicated that low-acetyl GGM dispersions formed gels (G′ > G″) at all other studied solid concentration and pH level combinations except 5 % and pH 4. High pH levels, leading to further removal of acetyl groups, and high solid concentration facilitated the gel formation. GGM hydrogels were weak gels with strong shear-thinning behavior and thixotropic properties, and high hardness and water holding capacity; which were enhanced with increased pH and solid concentration, and prolonged storage time. Our study showed the possibility to utilize low-acetyl GGM as mildly processed gelling or thickening agents, and renewable materials for bio-based hydrogels.Peer reviewe

Effects of pH and temperature of ultrafiltration on the composition and physicochemical properties of hot-water-extracted softwood galactoglucomannans

The recovery of softwood galactoglucomannans (GGM) by pressurized hot water extraction and further con-centration by membrane filtration followed by spray drying yield biopolymers suitable as raw materials for renewable products. GGM are often characterized as having low viscosity in water and excellent emulsion sta-bilizing capacity, enhanced by lignin structures co-extracted with GGM. To reduce membrane fouling during filtration and subsequently to increase product yield, the pH and temperature of GGM liquor can be increased, but effects of such conditions on properties of recovered GGM have not been well understood. Herein, we sys-tematically varied the ultrafiltration pH (6-10) and temperature (30-60 degrees C) and characterized the composition and physicochemical properties of spray-dried GGM powders in comparison with freeze-dried (fGGM) and ethanol precipitated GGM (eGGM). The GGM samples ultrafiltrated at 60 degrees C and pH 10 (GGM-10/60) showed lower molar mass (2200 Da), degree of acetylation (0.09) and absolute zeta-potential (13 mV) than the other ultrafiltrated samples at pH (6-10) and temperature (30-45 degrees C) (3200-3700 Da, 0.11-0.15 and 23-32 mV, respectively). These differences could explain the unique gel formation capacity of GGM-10/60 after ultra-sonication, which opens new prospects in GGM applications such as thickening agents or in 3D printing. The present results allow the design of biorefinery processes to obtain GGM with desirable properties for specific applications.Peer reviewe

Effects of pH and temperature of ultrafiltration on the composition and physicochemical properties of hot-water-extracted softwood galactoglucomannans

The recovery of softwood galactoglucomannans (GGM) by pressurized hot water extraction and further concentration by membrane filtration followed by spray drying yield biopolymers suitable as raw materials for renewable products. GGM are often characterized as having low viscosity in water and excellent emulsion stabilizing capacity, enhanced by lignin structures co-extracted with GGM. To reduce membrane fouling during filtration and subsequently to increase product yield, the pH and temperature of GGM liquor can be increased, but effects of such conditions on properties of recovered GGM have not been well understood. Herein, we systematically varied the ultrafiltration pH (6− 10) and temperature (30–60 ◦C) and characterized the composition and physicochemical properties of spray-dried GGM powders in comparison with freeze-dried (fGGM) and ethanol precipitated GGM (eGGM). The GGM samples ultrafiltrated at 60 ◦C and pH 10 (GGM-10/60) showed lower molar mass (2200 Da), degree of acetylation (0.09) and absolute ζ-potential (13 mV) than the other ultrafiltrated samples at pH (6− 10) and temperature (30–45 ◦C) (3200–3700 Da, 0.11–0.15 and 23–32 mV, respectively). These differences could explain the unique gel formation capacity of GGM-10/60 after ultrasonication, which opens new prospects in GGM applications such as thickening agents or in 3D printing. The present results allow the design of biorefinery processes to obtain GGM with desirable properties for specific applications.</p