Dephosphorylation-induced structural changes in β-casein and its amphiphilic fragment in relation to emulsion properties

To promote the understanding of the relationship between emulsifying and molecular properties of proteins/peptides, intact beta-casein (beta CN) and its amphipathic fragment, i.e., beta CN (1-105/107) were dephosphorylated. Dephosphorylation was found not to change significantly their emulsifying properties. Since it is known that the structure of proteins can change upon adsorption onto an interface, the secondary structure of intact beta-casein, its amphipathic fragment, and their dephosphorylated forms, both in solution and after adsorption onto a hydrophobic teflon/water interface, were studied by far-UV circular dichroism spectroscopy. An increased content of secondary structure, especially alpha-helix, was found for all samples after adsorption onto teflon. Dephosphorylation increased the helix-forming propensity, especially for amphipathic fragment of beta-casein. No influence of the secondary structure properties on the emulsion-forming and -stabilizing properties was observed, but a relationship between the maximum surface load and the emulsion-stabilizing properties was found. (C) 2000 Societe francaise de biochimie et biologie moleculaire / Editions scientifiques et medicales Elsevier SAS.