EXTRINSIC LABELING OF CASEINOPHOSPHOPEPTIDES WITH CA-45 AND RECOVERY FOLLOWING THERMAL-TREATMENT

The determination and degree of extrinsic labelling of tryptic derived caseinophosphopeptide with Ca-45 was performed in native and heat treated whole casein and skim milk protein powders. Two principal phosphopeptides, alpha(2)2 (1-21) and beta-casein (1-25) were identified by peptide sequencing following isolation by HPLC. These particular peptides accounted for similar Ca-45 binding activities in the crude CPP fraction. The application of a thermal process to casein and skim milk protein powder resulted in substantial dephosphorylation, but had little effect on both the yield and degree of extrinsic labelling of caseinophosphopeptides by Ca-45.