Physical and Oxidative Stability of Cod Liver Oil-in-Water Emulsions Stabilized with Whey Protein/K-Carrageenan Complexes

The stability of cod liver oil-in-water emulsions containing whey protein isolate (WPI) and kappa-carrageenan (kappa-car) complexes was investigated as a function of pH (3-7). The droplet electrical charge decreased as the kappa-car concentration increased at pH 3, 4, 5, and 6. The average droplet sizes at pH 3 and 4 for all kappa-car concentrations (0.05, 0.1, 0.2, or 0.4 wt %) were significantly (p < 0.05) larger than at pH 6 and 7. The viscosity of the emulsions at pH 3, 4, and 5 was significantly higher than the viscosity at pH 6 and 7. The viscosity of the emulsions increased as the kappa-car concentration increased from 0.05 to 0.4 wt % at pH 3, 4, and 5. The concentrations of lipid hydroperoxides and TBARS in emulsions were decreased by the addition of kappa-car (>= 0.1 wt %). The results suggest that WPI-kappa-car complexes could be used to improve the physicochemical stability of emulsions containing hydrophilic bioactive compounds.