Effects of soy peptides and pH on foaming and physicochemical properties of egg white powder

The effects of pH on the foaming properties of egg white powder (EWP) improved by soy peptides (SP) were investigated. After adding various amounts of SP (3%, 6%, 9%, 12%) and adjusting the pH (4, 5.5, 7, 8.5), SP + EWP solutions were characterized according to their physicochemical properties, rheological behaviors, foaming performance, and microstructure. The results showed that 9% and 12% SP could improve the foaming properties of EWP. A more uniform size, greater foam elasticity, higher surface hydrophobicity and more flexible secondary structure were obtained when up to 9% SP was added. This facilitated interface adsorption, thereby significantly improving the foaming ability and foam stability. The SP + EWP solution had the largest expansion degree, most flexible structure, fastest interface adsorption rate, and highest elasticity of the foam film at pH 7, leading to the optimal foaming ability and foam stability. It was concluded that the optimal foaming performance was obtained by adding 9% SP to EWP under neutral pH conditions.