What determines the foam stability of dilute protein solutions in sparging systems?

The growing demand for sustainable and functional ingredients in the food, pharmaceutical, and cosmetic industries has heightened interest in plant proteins as foaming agents. However, a knowledge gap persists regarding how transient material properties, influenced by foaming conditions, impact foam stability. This study investigates foam formation and stability of dilute pea protein solutions (0.1-1 wt%) using a gas sparging method. We examine the impact of protein properties, including bulk viscosity, adsorption kinetics, and foaming conditions like sparging flow rate, initial liquid volume, and sparging time. By correlating foam half-life (t(1/2)) with surface pressure at various time scales, we observed that transient surface pressure at residence time (pi(r)) strongly correlated with t(1/2) (R-2 = 0.94) over a wide range of foaming processing parameters (flow rate of 0.2-0.4 L/min, liquid volume of 30-150 mL, and sparging time of 5-10 s) and protein concentrations, unlike equilibrium surface pressure or surface pressure at sparging time. This highlights the significance of pi(r), as it directly relates to initial bubble size, in controlling foam stability for dilute protein solutions. Our results reveal key insights into how transient surface properties, influenced by foaming processing parameters, govern foam stability. These findings contribute to the broader understanding of plant protein functionality and offer potential strategies for enhancing their use in both food and non-food applications.