Influence of NaCl addition on the properties of emulsions formed with commercial calcium caseinate

Oil-in-water emulsions containing 30% soya oil, calcium caseinate and various NaCl concentrations were prepared in a two-stage homogeniser. The average volume-surface diameter (d32) of emulsion droplets decreased with increasing NaCl from 0 to 20 mM, but remained constant beyond 20 mM. The surface protein concentration (mg/m2) decreased with NaCl addition up to 50 mM, but increased with increasing NaCl concentration above 50 mM. αs-(αs1-+αs2-)Casein adsorbed at the droplet surface in preference to β-casein in emulsions made both with and without NaCl. In emulsions made with <2% calcium caseinate, the droplet size distributions were broad and bimodal, but they became narrow when 50 or 150 mM NaCl was added prior to emulsion formation. The changes in creaming stability were consistent with the droplet sizes in emulsions. It appears that the aggregated protein in calcium caseinate dispersion was dissociated by NaCl, which consequently improved its emulsifying properties.