The caseins: Structure, stability, and functionality

In bovine milk, and the milk from most other species, the caseins represent family of 4 gene products (αs1-, αs2-, β-, and κ-casein) and exhibit significant microheterogeneity due to genetic variation and posttranslational glycosylation and phosphorylation. In milk, the caseins are found predominantly in association colloids called casein micelles, which include micellar calcium phosphate that contributes to the integrity and stability of the micelles. Enzymatic destabilization of casein micelles or adjustment to their isoelectric point (pH 4.6) can result in coagulation or gelation; this is the principle by which cheese or yogurt are produced. In addition, the size of micelles allows their ready recovery from milk using membrane filtration, and caseins, collectively or individually purified, are widely used as ingredients in a wide range of food applications. In this chapter, the properties of the individual caseins, the casein micelles, and properties and applications thereof are reviewed.