Thin liquid films stabilized by plant proteins: Implications for foam stability

HYPOTHESIS: Plant-based proteins offer a sustainable solution for stabilizing multiphase food materials like edible foams and emulsions. However, challenges in understanding and engineering plant protein-stabilized interfaces persist, mostly because of the commonly poorer functionality and complex composition of the respective protein isolates. We hypothesize that part of the limited understanding is related to the lack of experimental data on the length-scale of the thin liquid film that separates two neighboring bubbles. By conducting such experiments, we aim to better understand the mechanisms by which plant proteins stabilize foams, a critical material in food applications. EXPERIMENTS: In this study, we employ the dynamic thin film balance method to study the equilibrium properties and dynamic drainage behavior of foam thin liquid films stabilized by proteins derived from two main plant protein sources, yellow peas and rapeseeds, to investigate potential differences in film stabilization. FINDINGS: Our thin film results provide new insights into the general foam stabilization mechanism of the two plant proteins. Most studies in this field focus on the impact of surface rheological parameters on stability of plant protein-based foam. We show that for such foams the half-life scales linearly with film thickness, the latter being closely related to the steric and electrostatic interactions developed across the respective films in equilibrium. Our study demonstrates the value of thin film studies in complementing traditional methods for studying protein-stabilized interfaces and facilitates an understanding of foam stabilization mechanisms that are universal among various surface-active species.