Dodecenyl succinylated alginate (DSA) as a novel dual-function emulsifier for improved fish oil-in-water emulsions

Alginate was chemically modified with dodecenyl succinic anhydride (SAC12) to produce an innovative emulsifier with antioxidant properties for use in fish oil-in-water emulsions. The modification reaction was conducted in an aqueous reaction system at low temperature and neutral pH. The resulting emulsifier had a degree of succinylation of 33.9 +/- 3.5% and the product was structurally verified by Fourier-transformed infrared (FTIR) spectrometric analyses. The surface activity of the DSA was confirmed by contact angle determinations in static drop shape analysis on a non-polar surface. The dodecenyl succinylated alginate (DSA) was applied as stabilizer of 30% fish oil-in-water emulsions. The emulsions' creaming stability was significantly increased compared to emulsions stabilized with native alginate or beta-lactoglobulin (BLG). Confocal laser scanning microscopy (CLSM) showed that DSA stabilized emulsions through adsorption to the oil-water interface, while native alginate stabilized emulsions by increasing the viscosity of the aqueous phase. Emulsions stabilized with DSA had a larger negative zeta potential compared to emulsions stabilized with native alginate or BLG, which provided repulsive forces between oil droplets, enhancing the emulsions' physical stability. DSA was found to inhibit lipid oxidation in emulsions, thus lowering the formation of secondary oxidation products by 79% compared to the control with no DSA. In all, this work presents a novel nature-based food emulsifier, which was found to have antioxidant and emulsion-stabilizing properties, thus representing a promising ingredient with application potential for efficient delivery of oxidation-susceptible oils. (C) 2014 Elsevier Ltd. All rights reserved.