Improvement of emulsification properties of sodium caseinate by conjugating to pectin through the Maillard reaction

Abstract

Sodium caseinate was covalently linked to apple pectin in a controlled dry state (60°C, 79% relative humidity) through the Maillard reaction. SDS-PAGE confirmed the covalent attachment between the protein and the polysaccharide. The emulsifying activity and stability of the resulting protein–polysaccharide conjugate were improved. The conjugate had better emulsification properties than those of sodium caseinate or pectin alone as well as those of the common commercial emulsifiers, gum arabic (GA) and glycerol monostearate (GMS), even when measured at elevated temperature, in high salt buffers or at low pH. The droplet size of the oil emulsions produced by the new conjugate was much smaller than the size of droplets in sodium caseinate or pectin emulsions. The ratio of free amino groups in the conjugate was less than that of the starting materials, due to the involvement of these groups in the Maillard reaction.