Cow Milk Proteins: Twenty-Five Years of Progress

TABLE 1. Nomenclature and selected characterizing properties of the important milk proteins as recognized in 1956. a Approximate percentage Mobility of milk Molecular at Component proteins weight PI c pH 8.6 d Distinguishing characteristics Po t7 t*. Caseins 78--85 z-Casein 45-63 ? 4.1 -6.7 fl-Casein 19-28 24,100 4.5 -3.1 7-Casein 3 -7 ? 5.8-6.0 --2.0 Whey proteins 15-25 ~3-Lactoglobulin e 7-12 35,500 5.18 --5.1 a-Lactalbumin 2--5 15,100 4.1-4.8 -4.2 "Blood serum albumin" .7-1.3 65,000 4.7 -6.7 Immune globulins: Euglobulin .8-1.7 180,000 6.0 --1.8 Pseudoglobulin .6-1.4 180,000 5.6 -2.0 to -2.2 Proteose-peptone fraction 2-4 ? Fat globule "membrane" protein .05-.10 Enzymes traces Acid precipitated whole casein (pH 4.6) 1.0% phosphorus .6% phosphorus .11% phosphorus 1.1% cysteine 7.0% tryptophan Identical to albumin of bovine serum Carry antibodies. Present in high concentrations in colostrum. Contain hexose and hexosamine. Contain hexose and hexosamine. Soluble in skim milk heated to 95C for 20 min.