Surface tension and foam stability of commercial calcium and sodium caseinates

The static and dynamic surface tension of sodium and calcium caseinates was compared with their foam behavior. The surface tension behavior of sodium and calcium caseinates was similar but the foaming properties differed. Caseinates presented moderate surface activity lowering the surface tension of water to 40 mN/m. The surface pressure vs. composition data were analyzed using a new surface equation of state and obtained 0.1% (w/v) critical concentration and the molecular surface area; in the case of calcium caseinate was larger compared to sodium caseinate. Caseinates were evaluated at the critical concentration by means of dynamic surface tension to compare their behavior; calcium caseinate took longer time to reach equilibrium conditions. Their foam behavior was transient type with maximum foamability around the critical concentration; sodium caseinate presented better foaming properties than calcium caseinate.