Casein micelles core-coat

Waugh and Noble (181) have proposed a coat-core model whereby the core of the micelle is comprised of calcium ag-caseinate covered by a coat of calcium s- and x-caseinates. However, the x-casein in the coat is oriented toward the outer surface of the micelle so that the hydrophilic macropeptide portion of the kappa casein would interact with the aqueous environment of the milk serum to stabilize the integrity of the individual micelles so that the micelles normally do not interact. 

At the same time, the hydrophobic portion of the K-casein interacts with the calcium as- and /3-caseinates to form coat subunits which interact strongly with the calcium 8-caseinate in the core. The micelles are pictured as solid, crenated spheres (Figure 7) whereby the available K-casein for the formation of coat subunits determines the average size of the micelles. 

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