Heat-induced changes in casein-derived phosphopeptides.

Phosphopeptides derived from casein may function as carriers for calcium and trace elements. In regard to such specific nutritive effects, the heat-induced changes in tryptic phosphopeptides liberated from bovine sodium caseinate as a model system were investigated. Both microwave and oven heating resulted in a marked loss of peptide-bound phosphorous (dephosphorylation) and a decrease of casein-phosphopeptides in the soluble part of the tryptic hydrolysate. It is concluded that hydrolysis of phosphoseryl to seryl residues was the prevailing degradation step to soluble proteolytic products, whereas lysinoalanyl-casein is claimed to be present almost exclusively in the pH 4.6-insoluble part of the tryptic digest.