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 th in 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 w as rapid, temperature sensitive, and chaotic, and the surface mobility of caseinate thin films also showed temperature sensitivity. The step wise drainage is thought to be due to the layering of lecithin-caseina te submicelle complexes. Lecithin-stabilized thin films showed similar drainage behavior and temperature sensitivity. However, the films wer e approximately 66% thinner than caseinate films, and surface diffusio n 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 wit h lipid), showed thin film properties similar to the commercial casein ate. Caseinate supplemented with lipid showed thin film drainage chara cteristics similar to caseinate, and surface mobility similar to lecit hin. The presence of lecithin in caseinate thin films causes an increa se in mobility, drainage, and stratification, along with a decrease in thin film thickness. This demonstrates that lecithin, possibly partia lly bound to the caseinate, is present at the interface disrupting pro tein-protein interactions. (C) 1998 Academic Press.