Formulation engineering of food model foams containing diglycerol esters and β-lactoglobulin

The foaming characteristics of low- molecular- weight emulsifiers ( LMWEs) and proteins are important attributes during the production, storage, transport, and consumer perception of quality ( appearance) of food dispersions ( emulsions and foams). In this article, we consider the analysis of interfacial ( adsorption isotherm and rate of adsorption) and foaming ( foaming power and foam stability) properties of a typical milk protein (beta-lactoglobulin) and diglycerol esters ( diglycerol monostearate and diglycerol monolaurate) as LMWEs, as a function of the foaming agent concentration in aqueous solution. We observed that the adsorption and foaming power ( foam capacity, gas and liquid retention in the foam, and foam density) increase with the foaming agent concentration in the aqueous phase. The adsorption kinetics at short adsorption times is diffusioncontrolled. However, the mechanism that controls the long- term adsorption is the penetration of the foaming agent at the interface. At surface pressures lower than that of monolayer saturation, the foaming is zero. A close relationship was observed between foaming and the rate of diffusion of the foaming agent to the airwater interface. The foam stability, quantified by the relaxation times due to drainage (t(d)) and disproportionation/ coalescence (t(d)), correlates with the equilibrium surface pressure (pi e) of the film adsorbed from aqueous solutions of the foaming agent.