Effect of Alkaline Earth Metals on the Crosslinking of Casein by Micellar Calcium Phosphate

¹ Department of Biochemical Science and Technology, Faculty of Agriculture, Kagoshima University, Kagoshima 890, Japan

Artificial casein micelles were prepared by adding 20 to 30 mM calcium, 17 to 22 mM phosphate, and 10 mM citrate to whole casein solutions. To casein micelles, 2.5 to 10 mM magnesium, strontium, or barium was also added. The content of the casein aggregates that were crosslinked by micellar calcium phosphate was determined by HPLC in the presence of 6 M urea, Magnesium phosphate alone had no crosslinking ability, but magnesium increased the amount of calcium phosphate and promoted the formation of crosslinking of casein by micellar calcium phosphate. The amounts of calcium and magnesium, which were bound to casein in casein aggregates crosslinked by micellar calcium phosphate, increased as magnesium concentration increased. When strontium and inorganic phosphate were added to whole casein solutions, casein aggregates that were crosslinked by strontium phosphate were formed even in the absence of calcium. Barium phosphate alone had no crosslinking ability. Barium restrained the formation of casein aggregates that were crosslinked by micellar calcium phosphate. We concluded that alkaline earth metals in addition to calcium affected crosslinking of casein by micellar calcium phosphate.

Key Words: casein micelle • calcium phosphate • crosslinking

Submitted on August 8, 1994
Accepted on April 10, 1995