gammacaseins

Gamma-caseins are a class of milk proteins that originate as proteolytic fragments of beta-casein rather than as separate gene products. In native milk, the major casein types are alpha-s1-, alpha-s2-, beta-, and kappa-caseins; gamma-caseins arise when specific enzymes cleave beta-casein, producing a family of gamma-related fragments that vary in length and terminal composition.

The formation of gamma-caseins is driven by proteolytic enzymes present in milk or introduced during processing and digestion. Plasmin, an intrinsic milk protease, along with microbial or rennet-derived proteases, can cleave beta-casein to yield gamma1-, gamma2-, gamma3-casein fragments. These fragments are commonly more abundant in aged milk, ripened cheeses, and fermented dairy products where proteolysis has progressed.

Physicochemical properties of gamma-caseins differ from intact beta-casein; as fragments they are typically less tightly associated with the casein micelle, which can influence the stability of the protein network. Their presence can affect milk coagulation and cheese texture by altering proteolysis patterns and micellar behavior during processing and aging.

Nutrition and health aspects are linked to peptides released from caseins during digestion. Some beta-casein-derived fragments, including gamma-casein-derived peptides, can yield opioid-like peptides known as casomorphins under certain conditions. The clinical significance of these peptides remains a subject of debate, and evidence is not conclusive. Gamma-caseins themselves are not considered essential nutrients.

See also: casein, beta-casein, plasmin, dairy protein digestion