Response surface analyses of the effects of calcium and phosphate on the formation and properties of casein micelles in artificial micelle systems

Artificial casein micelles were prepared ata casein concentration of 2.5% by adding calcium, phosphate, and citrate to sodium caseinate solution. The final calcium, phosphate, and citrate concentrations in micelle systems were 15-40, 0-30, and 10 mM, respectively. The number of prepared artificial micelle samples was 42. The predicted equations for micellar casein, micellar calcium, micellar phosphate, casein aggregates cross-linked by micellar calcium phosphate, and serum casein released on cooling were formulated using a second-order model by multiple regression techniques. Perspective views and cross-sectional views of response surfaces were constructed from the equations. Although micelle formation depended strongly on calcium concentration, the effect of phosphate was obvious, especially at low calcium concentrations. Perspective views of response surfaces for micellar calcium, micellar phosphate, and casein aggregates cross-linked by micellar calcium phosphate were very similar, and they increased with increases in calcium and phosphate concentrations. Serum casein released from micelles on cooling decreased with increases in calcium and phosphate concentrations. The combined effects of calcium and phosphate on the formation and properties of casein micelles were clearly demonstrated by multiple regression and surface response analyses.