Mechanism of sodium alginate synergistically improving foaming properties of pea protein isolate: Air/water interface microstructure and rheological properties

The synergistic effect of polysaccharides plays a crucial role in regulating the foaming properties of protein based aerated foods. In this study, the synergistic improvement mechanism of pea protein isolate (PPI)-sodium alginate (SA) composite on the foaming performance was determined through multi-component interaction, air/water interface adsorption behavior and foam properties. The results of interactions between PPI and SA indicated that SA and PPI could form smaller and more stable soluble composite through hydrogen bonding, hydrophobic interactions, and electrostatic interactions. The alpha-helix content of PPI significantly decreased, and PPI exhibited a more flexible secondary structure. In depth research on the air/water interfacial behavior and interfacial microstructure through adsorption kinetics, surface dilatational rheology and Lissajous plots indicated that the PPI-SA composite could accelerate the adsorption process, constructing a highly viscoelastic interface mainly based on elasticity. The results of foam properties showed soluble PPI-SA composite could prepare smaller and more dense foam with thicker and smoother interface film, which was beneficial to the foam stability. The results of small amplitude oscillatory shear and large amplitude oscillatory shear suggested that foam prepared by soluble PPI-SA composite showed stronger ability to resist deformation whether in linear or nonlinear viscoelastic region, revealing the good mechanical properties of these foam under extreme processing conditions and feasibility to improve the quality of aerated food. When the mass ratio of PPI/SA was 1:0.3, the foam properties was strongest. When the mass ratio of PPI/SA exceeded 1:0.3, insoluble substances appeared in the composite system, which was disadvantageous to foam properties and deformation resistance. Therefore, the complexation of PPI and SA was an effective way to improve the air/water interface and foaming properties of PPI, providing theoretical guidance for targeted regulation of the foaming properties of protein based aerated foods.