Abstract
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.
Highlights
The market of food hydrocolloids is growing rapidly, and its value is expected to reach $7.56 billion by 2020 (MarketsandMarkets, 2016)
Not limited to spruce GGM, this method can be used as a general concept for other wood hemicelluloses
Information on GGM's function mechanism is important for biorefineries regarding adjusting the extraction and isolation conditions, as well as for industries in product development
Summary
The market of food hydrocolloids is growing rapidly, and its value is expected to reach $7.56 billion by 2020 (MarketsandMarkets, 2016). Hydrocolloids are integral ingredients in a wide range of processed food products and beverages and include polysaccharides from plants, seaweeds, microbes, plant exudates, and modified biopolymers from starch, and cellulose. Most are high-molar-mass hydrophilic biopolymers and are able to stabilize emulsions by modifying the rheological properties of continuous phase. A few of them (namely, gum arabic, some pectins, some galactomannans, modified starch, and modified cellulose) function as emulsifiers (Dickinson, 2003). Gum arabic is an established hydrocolloid emulsifier but an expensive ingredient, and replacements such as corn fiber gum, an arabinoxylan (hemicellulose)-rich product from corn milling, are being sought (Yadav, Johnston, Hotchkiss, & Hicks, 2007)
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