Absolute quantification of human milk caseins and the whey/casein ratio during the first year of lactation

ABSTRACT: Whey proteins and caseins in breast milk provide bioactivities and also have different amino acid composition. Accurate determination of these two major protein classes will therefore provide a better understanding of human milk composition and function and also aid in developing improved infant formulas based on bovine whey proteins and caseins. In this study, we implemented a LC-MS/MS quantitative analysis based on iBAQ label free quantitation to estimate absolute concentrations of alpha-casein, beta-casein and kappa-casein in human milk samples (n=88) collected between day 1 and day 360 post partum. Total protein concentration measured by ninhydrin-based amino acid analysis ranged from 2.03 to 17.52 with a mean of 9.37�3.65 g/L. Casein subunits ranged from 0.04 to 1.68 g/L (alpha-), 0.04 to 4.42 g/L (beta-), and 0.10 to 1.72 g/L (kappa-), with beta-casein having the highest average concentration among the three subunits. Calculated whey/casein ratio ranged from 45:55 to 97:3. Linear regression analyses show significant decreases in total protein, beta-casein, kappa-casein, total casein, and whey/casein ratio during the course of lactation. Our study presents a novel and accurate analysis of human milk casein content, demonstrating a lower casein content than earlier believed, which has implications for improved infants formulas.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (ncbitaxon:9606)

SUBMITTER: Bo L�nnerdal  

PROVIDER: MSV000081195 | MassIVE | Fri Jun 23 16:06:00 BST 2017

SECONDARY ACCESSION(S): PXD006796

REPOSITORIES: MassIVE