Amphiphilic hemicellulose derivatives as stabilizers in oil-in-water emulsions

Using hemicelluloses, the most abundant water-soluble polysaccharide found in biomass, this study developed amphiphilic derivatives from an undervalued side stream commonly found in biorefinery processes. Specifically, galactoglucomannans (GGM), the main hemicellulose type in most softwood species, were used as the hydrophilic moiety of the amphiphilic derivative. Naturally occurring fatty acids (FA) pre-activated with 1,1′‑carbonyldiimidazole (CDI) were grafted to the backbone of GGM through esterification. The physiochemical properties of the functionalized GGM (GGM-FA) were investigated and tailored, by applying three different FA chain lengths (C9, C14, C18) and two different GGM to fatty acid molar ratios (1:0.07 and 1:0.14). The GGM-FA was further investigated as a stabilizer in a model oil-in-water emulsion. This study shows that functionalization of the GGM by grafting FA onto GGM results in amphiphiles that can successfully be used as stabilizers for oil-in-water emulsions, keeping the emulsions stable for up to six weeks. The emulsion stability effect was more pronounced with longer chain lengths of the fatty acid, and a higher molar mass ratio of 1:0.14 was preferred. This study demonstrates a strategy for the design of fully bio-based surface-active stabilizers that possess tunable amphiphilicity, opening up numerous opportunities for formulating emulsions and more broadly dispersions.