Bulk, Foam, and Interfacial Properties of Tannic Acid/Sodium Caseinate Nanocomplexes

For this work, the aim was to investigate the adsorption of the tannic acid (TA)/sodium caseinate (SC) nanocomplexes at the air/water interface and then to research its relationship with foam properties. First, nanocomplexes were prepared in a different mass ratio of TA and SC. The bulk behavior of nanocomplexes was evaluated by dynamic light scattering (DLS), signal-intensifying fluorescence probe (ANS), etc. As the concentration of TA increased, the z-average siameter (D-z) of TA/SC nanocomplexes decreased gradually and the negative charge increased. Meanwhile, the surface hydrophobicity (S-o) of the SC also decreased after the addition of TA. The interfacial properties were determined by dynamic surface tension and dilational rheology. The presence of polyphenols decreased the surface pressure (pi) that resulted in poor foamability. However, the elastic (E-d) component of the dilational modulus of films also increased as polyphenols concentration increased, which gave rise to admirable foam stability. The contribution of polyphenols to stabilize foam columns may be caused by interfacial interaction between proteins and polyphenols.