Immunochemical evaluation of bovine beta-casein and its 1-28 phosphopeptide in cheese during ripening.

Polyclonal antibodies raised against the plasmin-released 1-28 phosphopeptide from bovine beta-casein [i.e., beta-CN(f1-28)4P] specifically recognized the tryptic beta-casein 1-25 and 2-25 peptides, whatever the degree of phosphorylation, but were unresponsive to the shortened beta-casein 16-22 phosphopeptide. These antibodies were able to recognize the parent bovine beta-casein as well as the homologous water buffalo protein, but they could not detect the homologous counterparts from ovine and caprine milks. Such antibodies were used in competitive enzyme-linked immunosorbent assays to monitor the plasmin-mediated release of the 1-28 phosphopeptide from beta-casein and to evaluate the residual native beta-casein in bovine cheese sampled during ripening. Applications of these polyclonal antibodies are suggested mainly for estimating the age of hard cheeses and, possibly, for tracing the presence of bovine casein in fresh ovine and caprine cheeses.