Wood hemicelluloses are a group of abundant raw materials that can be isolated from forest industry side streams such as sawdust. In terms of chemical structure, hemicelluloses are a heterogenic group of carbohydrates, and their structures are related to the wood source. In general, galactoglucomannans (GGM) are isolated from spruce, and glucuronoxylans (GX) from birch. Residual lignin is very often co-extracted with hemicelluloses, for example during pressurized hot water extraction (PHWE).<br/><br/>Hemicelluloses can be exploited as hydrocolloids, which can stabilize emulsions in various applications, such as in food, pharmaceuticals, and paints. Hemicelluloses, such as GGM, provide excellent physical and oxidative stability for rapeseed oil-in-water emulsions. The aims of this study were: first, to investigate the chemical identity of phenolic residues co-extracted with hemicelluloses from the PHWE process, and secondly, to gain knowledge on the effect of these residues on the physical and oxidative stability of emulsions.<br/><br/>GGM and GX were fractionated to obtain concentrated phenolic residues as one fraction, and partially purified hemicelluloses as the other fraction. According to nuclear magnetic resonance (NMR) analysis, the phenolic-rich fraction contained the typical bonding patterns of lignin. Oil-in-water emulsions were prepared from stripped rapeseed oil, and original hemicelluloses or partially purified hemicellulose fraction as the emulsifier. The emulsion stability was followed for three months, by monitoring the changes in droplet size distribution to obtain results for physical stability, and by measuring the peroxide value to gain knowledge on oxidative stability. The emulsions containing more lignin were more resistant towards oxidation, as could be expected because of the radical scavenging properties of lignin. Interestingly, GGM and GX affected the droplet size of emulsions in different ways, and lignin showed also functional role in the physical stability of emulsions.

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

2019 Spring National Meeting

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