Air-water interfacial properties and quantitative description of pea protein isolate-Tween 20

The air-water interfacial properties of pea protein isolate (PPI) and Tween 20 (T20) were investigated in this study. The result of dynamic foam analyzer showed that the foam prepared by 0.5%PPI-0.1%T20 exhibited higher foam stability at 30 min and uniform bubble size distribution. The protein displacement by Tween 20 at the air-water interface was observed by atomic force microscopy (AFM) through the imaging of Langmuir-Blodgett (LB) films. During the displacement of pea protein isolate by the nonionic surfactant Tween 20, the surface pressure was increased while the complex surface dilatational modulus was decreased. Based on the AFM observations of the LB films, the quantitative analysis indicated the increased protein quantity in the foam network. To be emphasized, the formation of protein network at the plateau border of foams contributed to the increased foam stability. The AFM results showed that the protein at the air-water interface could be replaced by T20, but comparing with the PPI-stabilized foam, the addition of 0.1% T20 could increase the relative quantity of vicilin, thus leading to the increase of interconnected protein network at foam film to improve the foam stability. The research could promote the understanding of protein displacement by Tween 20 at the air-water interface, which could improve the quality of protein-surfactant stabilized foam-based foods.