Effect of liquid fraction and bubble size distribution on the polarised light scattering characteristics of Casein foam

Abstract

A polarised light scattering experimental set-up was designed to conduct experiments using Casein foams with monodispersed and bidispersed bubble size distributions. Foams were initially generated under forced drainage conditions to maintain a uniform axial liquid fraction profile. Subsequently, the foams entered a free drainage period. During this period, the liquid fraction, the bubble size distribution and the polarisation parameters of scattered light due to the foam were measured individually. It was found that both the liquid fraction and the bubble size distribution of Casein foams varied simultaneously with drainage time. Therefore, multiple regression analysis was performed to investigate the individual effect of these two foam factors on the polarisation state. Four of the polarisation parameters (degree of polarisation, degree of linear polarisation, degree of circular polarisation, ellipticity angle) were shown to be associated with the liquid fraction and/or the bubble size distribution to different extents. However, the remaining parameter, orientation angle, was completely independent of the liquid fraction and the bubble size distribution. These results can be used for the development of the polarised light scattering method in the study of protein foams.