COMPARATIVE-STUDY OF CASEIN CONTENT IN HUMAN COLOSTRUM AND MILK

Analysis of casein content was carried out in human colostrum samples (1st to 3rd day of lactation) and in mature milk (1 month after partur ition). Casein pellets were obtained by ultracentrifugation of skimmed milk, and each component was identified by direct N-terminal sequenci ng after denaturing polyacrylamide gel electrophoresis and Western Blo tting on ProBlott membrane. Unlike mature milk, colostrum pellets do n ot contain any protein belonging to the casein group or subunits, but only some precipitated typical whey proteins. The absence or the prese nce of casein micelles in mammary secretions is proposed as discrimina ting element for unequivocal definition of colostrum and milk, respect ively.