Phosphopeptides derived from digests of milk casein possess bioactive properties with gastrointestinal, immunological, vasoregulatory and nutritional activities (Clare & Swaisgood, 2000; Kitts & Weiler, 2003). Products of tryptic digestion of casein, yielding caseinphosphopeptides (CPP), bind to divalent minerals such as iron and calcium by ionic interactions that involve phosphoseryl residues (Kitts & Yuan, 1992; Aìt-Oukhartar, 2000). Distribution of phosphoserine moieties varies with the individual native caseinates, and the extent of phosphorylation directly influences CPP mineral binding affinity (e.g. αs2>, αs1>β-caseins). The anionic pentapeptide (SerP-SerP-SerP-Glu-Glu) is the distinctive feature for the major fractions of casein phosphopeptides (CPP) characterized both in vitro and in vivo. Common CPP derived from tryptic digests of whole bovine casein in vitro include, β-casein-4P (1–25), αs1-casein-5P (59–79), αs2-casein-4P (1–21) and αs2-casein-4P (46–70) (Kitts & Kwong, 2004).
