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Re‐evaluation of the whey protein/casein ratio of human milk
Author(s) -
Kunz Clemens,
Lönnerdal Bo
Publication year - 1992
Publication title -
acta pædiatrica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 115
eISSN - 1651-2227
pISSN - 0803-5253
DOI - 10.1111/j.1651-2227.1992.tb12184.x
Subject(s) - lactation , casein , whey protein , kjeldahl method , polyacrylamide gel electrophoresis , chromatography , food science , zoology , chemistry , biochemistry , biology , nitrogen , enzyme , pregnancy , genetics , organic chemistry
Total casein subunits as well as whey proteins were quantitated in human milk samples during lactation. Two independent methods were used: precipitation at pH 4.3 in the presence of Ca 2+ followed by Kjeldahl analysis and polyacrylamide gradient gel electrophoresis (PAGGE) followed by densitometric scanning. Both methods yielded similar results: casein synthesis is low or absent in early lactation, then increases rapidly and subsequently decreases. The concentration of whey proteins decreases from early lactation and continues to fall. These changes result in a whey protein/casein ratio of about 90: 10 in early lactation, 60: 40 in mature milk and 50: 50 in late lactation. These observations indicate that the synthesis and/or secretion of caseins and whey proteins is regulated by different mechanisms. In addition, the relative proportion of the different β‐ and k ‐casein subunits was found to vary throughout lactation.