The Effects of Caseinate Submicelles and Lecithin on the Thin Film Drainage and Behavior of Commercial Caseinate.

The drainage behaviour (stratification, thickness, and mobility) of thin foam films stabilized by commercial caseinate was studied in 10 mM phosphate buffer at pH 7.0. Thin films of commercial caseinate drained in a stepwise manner, with steps of similar thickness. The drainage was rapid, temperature sensitive, and chaotic, and the surface mobility of caseinate thin films also showed temperature sensitivity. The stepwise drainage is thought to be due to the layering of lecithin-caseinate submicelle complexes. Lecithin-stabilized thin films showed similar drainage behavior and temperature sensitivity. However, the films were approximately 66% thinner than caseinate films, and surface diffusion was very rapid. Removal of lipid from caseinate dramatically affects the thin film drainage properties and reduces temperature sensitivity. Reconstituted caseinate (i.e., extracted caseinate reconstituted with lipid), showed thin film properties similar to the commercial caseinate. Caseinate supplemented with lipid showed thin film drainage characteristics similar to caseinate, and surface mobility similar to lecithin. The presence of lecithin in caseinate thin films causes an increase in mobility, drainage, and stratification, along with a decrease in thin film thickness. This demonstrates that lecithin, possibly partially bound to the caseinate, is present at the interface disrupting protein-protein interactions. Copyright 1998 Academic Press.