Studies on the Mineral Composition of the Casein Micelle of Cow's Milk by Gel Filtration

Abstract

Casein micelle was separated with distilled water through a column of Sephadex G-150 and identified by polyacrylamide gel electrophoresis. The amount of mineral ions removed from the micelle was approximately 100%, 100%, 91% and 50% in potassium, citrate, sodium and magnesium respectively, which were bound to carboxyl groups. Ester phosphate ions were not removed at all. Calcium and inorganic ions were hardly removed, and were only 37% as colloidal calcium phosphate. It appears that the phosphate com-ponent consists of two parts: a layer of ionic bonds (about 63%), and an absorption-layer (about 37%), bound weakly by Van der Waals' forces. The reversibility was compared between G-150, and colloidal phosphate-free micelles dialyzed in the original milk. The reversibility of both micelles was about 74 to 153% in all ions, except calcium and inorganic phosphate ions. The reversibility of calcium ions was about 28 to 29% in both micelles; that of the inorganic phosphate ions was higher, about 74%, in G-150 micelle, and lower, about 16%, in CPF micelle. It is presumed that the carboxyl groups of CPF micelle are combined with other groups as ionic or hydrogen combination.