Properties of emulsions stabilised by sodium caseinate-chitosan complexes

Oil-in-water emulsions (10%, w/w, oil) were prepared at pH 5.7 by using electrostatically formed complexes of 0.5% (w/w) sodium caseinate (Na-CAS) and 0-0.6% (w/w) chitosan. Emulsions stabilized by complexes with increased levels of chitosan (>0.2% w/w) had a smaller average droplet size and exhibited greater stability during storage. All chitosan containing emulsions exhibited a slight shear thinning behaviour with increased high-shear-rate viscosity at higher chitosan levels. Even though complexing of Na-CAS with chitosan resulted in a delay of the adsorption of the surface active components at the oil/water interface, the presence of chitosan did not significantly influence the rheological properties of the formed interfaces. Acid-induced aggregation was observed only for the emulsion that was stabilized solely by Na-CAS when the pH dropped close to the isoelectric point of the protein component, resulting in flocculation and large increase in the storage modulus. (C) 2012 Elsevier Ltd. All rights reserved.