Improving emulsion stabilizing capacity of sodium caseinate by colloidal lignin particles near the isoelectric point

Abstract

Sodium caseinate (Cas) is an attractive candidate for food emulsion formulation due to its surface-active properties as well as the ability to prevent the oxidation of encapsulation oils. However, the emulsions underwent destabilization near its isoelectric point (pI, around pH 4.8) due to the lack of enough electronic repulsion. To overcome the drawback, colloidal lignin particles (CLPs) fabricated from dietary fiber with superior negative repulsion and abundant surface active sites will be inspiring as the patch of Cas-based emulsion. This study systemically explored the modified effect of varied CLPs concentrations in the Cas-based emulsions prepared at pH 4.8. Due to hydrophobic attractions and hydrogen bonds between protein and CLPs, the CLPs significantly increased the negative charge and viscosity of composites while reduced surface hydrophobicity of Cas. Thus, in contrast to Cas, Cas/CLPs complex can fabricate a more elastic oil-water interfacial film, accompanying with a reduced droplet size (52–136 μm). Despite the inhibition of Cas adsorption at interfacial film, Cas/CLPs complex increase the stability of emulsion mainly by increasing electrostatic repulsion, enhancing film elasticity, and thickening continuous phase. Emulsions fabricated with Cas/CLPs complex effectively protected polyunsaturated fatty acids from deterioration, with the lowest levels of hydroperoxide and malondialdehyde observed in Cas/1.00 %CLPs emulsion. This study uncovered the facts behind the non-covalent interactions of Cas and lignin and proposed a novel strategy to stabilize Cas-based emulsions in acidic conditions.