Surface activities at the air‐water interface and the emulsifying and foaming properties of sodium caseinate, conventional casein‐whey protein co‐precipitate prepared from milk heated at 90°C × 15 min at pH 6.6 and milk protein isolates prepared from milks heated at 90°C × 15 min at pH 7.5 or at 60°C × 3 min at pH 10.0 were determined. The surface activities of the four proteins at the air‐water interface were similar, while the emulsifying capacity and emulsion stabilizing ability of casein was less than that of the milk protein isolates or the conventional co‐precipitate. Fat surface areas formed on emulsification with the four proteins were similar and increased with increasing power input. Total protein adsorbed at the interface and protein load (mg protein/m2fat) for the emulsions stabilized by sodium caseinate and the milk protein isolate prepared from the milk heated at 90°C × 15 min at pH 7.5 were similar and lower than those for emulsions stabilized by the other two proteins. Foam overruns followed the order: sodium caseinate>milk protein isolate prepared from milk heatedat90°C × 15min, pH 7.5>milk protein isolate prepared from milk heated at 60°C × 3 min, pH 10.0>conventional co‐precipitate, while foam stabilities fol