Casein micelles hairy micelle model

Historically, ideas of casein micelle structure and stability have evolved in tandem. In the earlier literature, discussions of micellar stability drew on the classical ideas of the stability of hydrophobic colloids. More recently, the hairy micelle model has focused attention more on the hydrophilic nature of the micelle and steric stabilization mechanisms. According to the hairy micelle model, the C-terminal macropeptides of some of the K-casein project from the surface of the micelle to form a hydrophilic and negatively charged diffuse outer layer, which causes the micelles to repel one another on close approach. Aggregation of micelles can only occur when the hairs are removed enzymatically, e.g., by chymosin (EC 3.4.23.4) in the renneting of milk, or when the micelle structure is so disrupted that the hairy layer is destroyed, e.g., by heating or acidification, or when the dispersion medium becomes a poor solvent for the hairs, e.g., by addition of ethanol. 

FIGURE 7.2 Calcium phosphate nanocluster model of a casein micelle. Substructure arises from the calcium phosphate nanocluster-like particles in the micelles (dark spheres). There is a smooth transition from the core to the diffuse outer hairy layer that confers steric stability on the micelle. (Courtesy of Holt and Roginski, 2001.)... 

Gel-like structure is another model that states casein molecules are located in micelle in a tangle manner and comphcated situation, forming a sphere. In addition, /c-caseins stretch out of the micelle and form a hairy layer. In this model, which was proposed by Holt [35], calcium phosphate nanoclusters act as linkers of thread-like casein monomers by cross-linking [2, 29, 36, 37]. In this model the calcium phosphate nanoclusters are responsible for linking the caseins molecules to each other whereas in previous proposed model nanoclusters are the joiners for submicelles. 

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