Study on sodium caseinate foam stability by multiple light scattering

摘要

Foams stability is a critical property for food applications. The main destabilisation processes of liquid foams are drainage, disproportionation and collapse. In the present work, destabilisation of foams prepared with sodium caseinate dispersions (2-10% w/w) were studied by multiple light scattering (Quick Scan). Results were corroborated by optical microscopy and a traditional volumetric method. Kinetics of drainage and collapse were fitted by the empirical equation alpha(t): alpha(max).t(n)/(t(n) + t(n) 1/2) where alpha(t) refers to the volume of drainage liquid (alpha(t)=V(t)) at time t or the normalised area of collapse (alpha(t) = A(c)(t)) at time t, while alpha(max) refers to the maximum volume of drained liquid (alpha(max) = V-max) or the maximum collapse area (alpha(max) = A(max)), n describes the sigmoidal character of the curve and t(1/2) is the half-life of drainage or collapse, respectively. Disproportionation kinetics was fitted by the exponential decay model BS(t) = a +b exp(-t/k), where BS(t) is the backscattering as a function of time, b refers to the maximum BS and k is inversely related to BS fall rate. From the results obtained it was possible to obtain parameters for destabilisation kinetics and determine the global stability of foams, which increase with the protein concentration.