Formation of interfacial milk protein complexation to stabilize oil-in-water emulsions against calcium

Abstract

Oil-in-water emulsions (30% soya oil) stabilized by sodium caseinate or whey protein were destabilized in the presence of calcium, whereas lactoferrin-stabilized emulsion was stable under same conditions. At pH7, addition of lactoferrin to the caseinate or whey protein-stabilized emulsions led to association of lactoferrin with adsorbed proteins by electrostatic interactions, hence resulted in the formation of lactoferrin-caseins/whey protein interfacial complexes at the interface of the emulsion droplets. The stability of the interfacial complexes-coated emulsion droplets in the presence of Ca2+ was examined by determination of particle size, zeta-potential and microstructure as a function of Ca2+ concentration and added lactoferrin concentration. For emulsions made with 1% w/w caseinate or WPI, the stability of emulsions in the presence of 20mM CaCl2 has been improved markedly after addition of 0.2% w/w lactoferrin, suggesting the small amount of lactoferrin on the interface can largely enhance the calcium stability of milk proteins-coated emulsion droplets. Steric repulsion between the interfaces of droplets produced by the large lactoferrin molecules on the interface was considered to contribute the preventing the flocculation caused by Ca2+ binding and reduction in the electrostatic repulsion between the emulsion droplets.