Casein k
Among the most studied casein is casein k (k-CN), probably
because of its importance in the stability of the micelle and
its role in dairy processing. The k-CN is also the only casein
having carbohydrate residues in its constitution (Fox and
Mulvihill, 1992). Caseins (α, β and κ) in the presence of
calcium phosphate, form stable casein micelles (colloidal
phase), which are balanced with the soluble phase of milk
(St. Gelais et al., 1992). It is possible to adjust the balance in
terms of temperature, pH and the addition of salts. So long
as the lactic acid bacteria converts lactose into lactic acid, it
lowers the pH of the milk thereby decalcifying the casein
micelles. There is another way to destabilize casein micelles
and it is by using an enzyme such as chymosine.