Effect of different salts on the foaming properties of model protein systems for infant formula

This multiscale study aimed to evaluate the effect of different salts (NaCl, KCl, MgCl2, and CaCl2) on foaming capacity (FC) and foam stability (FS) of model protein system (MPS) for infant formula via the changes of surface and structural properties. Results showed that the FC and FS of MPS were increased at NaCl, KCl, and MgCl2 condition, whereas CaCl2 significantly (P < 0.05) decreased FC (79.5 ± 10.6%) and increased FS (93.2 ± 2.2%). The H0 was increased, while the net charge and surface tension was reduced after addition of salts. Structural analysis revealed the reduction of intensity of intrinsic fluorescence spectroscopy and UV (UV) absorption, and the conversion of α-helix into β-strand, which was attributed to protein agglomeration. Additionally, MgCl2 and CaCl2 exhibited larger size and lower net charge compared with NaCl and KCl, indicating a greater ability to bind to charged amino acids and formed larger aggregates. Correlation analysis indicated that FC was positively related to adsorbed protein and β-turn, while negatively correlated with particle size. FS showed a positive correlation with β-strand, apparent viscosity, and zeta potential. However, it exhibited a negative correlation with β-turn, α-helix, and SH content. These results provide a theoretical reference for further understanding of the effect of salts on the foaming properties of MPS.