Sodium caseinate-stabilized emulsions: Factors affecting coverage and composition of surface proteins

As the concentration of caseinate in sodium caseinate-stabilized emulsions increased, the protein surface concentration increased. It plateaued at 1.36 +/- 0.05 mg/m(2) at a caseinate concentration between 2 and 4% (w/w), but the surface protein concentration markedly increased as caseinate concentration rose from 5 to 7.5%. At caseinate concentration below 2%, beta-casein adsorbed at the surface of oil droplets in preference to other caseins. Increasing the oil concentration from 10 to 30% (w/w) decreased the surface protein concentration from 3.7 +/- 0.3 to 1.4 +/- 0.04 mg/m(2), but further increases in oil concentration had much less effect. A decrease in surface protein concentration was observed as the homogenization pressure increased from 34 to 136 bar, but higher pressures had no further effect. beta-Casein was adsorbed preferentially at the droplet surface in emulsions homogenized at pressures above 204 bar. Addition of calcium chloride to sodium caseinate solutions above 0.08% w/w resulted in formation of large casein particles/aggregates which adsorbed on to the droplet surface causing higher surface protein concentration.