Foaming properties of skim milk powder fortified with milk proteins

The effect of different concentrations of added sodium caseinate (Na-Cas) and whey protein concentrate (WPC) on the foaming properties of reconstituted skim milk powder (SMP) was studied, to quantify practical applications as additives in aerated foods. Density and viscosity of the samples increased with increasing concentration of SMP or protein. The pH of the fortified products were close to those of the reconstituted SMP at 10%. The surface tension of both reconstituted SMP alone, and that fortified with WPC was higher than that of reconstituted SMP fortified with Na-Cas; these samples also took more time to reach equilibrium. Foaming capacity increased with increased SMP or protein. Despite the low surface tension attained at equilibrium of reconstituted SMP with increasing Na-Cas concentration, foam stability decreased. The kinetics of drainage, Ostwald ripening, and the collapse of bubbles were calculated. The most stable foams were those from reconstituted SMP fortified with WPC.