Foaming properties of different forms of caseins in aqueous systems

Foaming properties of sodium caseinate (NaCas) particle dispersions, native NaCas solutions, and casein micelle dispersions were investigated by visual observations and by considering viscosity and structural differences. The effect of NaCl on the foaming properties of systems was also discussed. The presence of NaCl (50 mM, 100 mM, and 200 mM) changed the foam stability of NaCas particle dispersions and native NaCas solutions, whereas foam stability of casein micelle dispersions was not affected by the presence of salt. When there was no NaCl addition to the systems, NaCas particle dispersions showed the highest foam stability (~ 3 h), whereas when there was NaCl in the medium, native NaCas solutions showed the highest foam stability (~ 2 h). The presence of salt ions changed the repulsive forces between proteins, which could result in a partial disintegration of particles and aggregation of native proteins. The presence of both particles and their dissociated aggregates in NaCas particle dispersions was found to increase the foaming properties. The behavior of NaCas particles at the interface was similar to the colloidal particles, which was different from the behavior of native proteins. Therefore, the NaCas particles have the potential to be used as a food-grade Pickering stabilizer in aerated food products.