Influence of Energy Density on Foamability: Comparison of Three Foaming Methods

The aim of the following study was to compare three different foaming methods and investigate the influence of the applied energy density (E_vol) on the following foam properties: foam capacity (FC), sauter-diameter (d_3,2) and interfacial area (IA). Foams were prepared with sodium caseinate, porcine gelatin, and egg albumen (c = 1-10 wt%) by whipping, spraying, and sparging employing up to 5 different E_vol (3.3 × 10⁴ J m^-3-4.0 × 10⁸ J m^-3). First, whipping resulted in a FC that depended on the protein concentration and the type of protein with gelatin having the highest FC (837.2% ± 89.5%) at 1 wt% among used the proteins. There was no linear trend between FC and concentration of gelatin whipped foams. In contrary, egg albumen whipped foams revealed a linear relationship between FC and concentration, with the highest foam capacity at c = 10 wt% (675.7% ± 83.0%). An increase in E_vol led to an increase in FC and in IA, but in a decrease in d_3,2 for all whipped foams. Second, spraying showed for all proteins an increase in FC with increasing concentration up to a plateau at >5 wt% (caseinate), >2 wt% (gelatin), >2 wt% (egg albumen). No clear correlation between foam properties and E_vol was observed for spraying. Third, sparging yielded a FC that was less affected by concentrations used in this study. Increasing the E_vol during sparging led to a higher FC and IA, while the d_3,2 slightly increased. Overall, no correlation between the methods, proteins, and energy density was obtained because the protein structure and foaming method influenced the foamability. However, E_vol in combination with IA as output parameter was shown to be most suitable to compare the foamability of the proteins and the methods.