Analysis of Free Amino Acids and Protein Contents of Mature Human Milk from Turkish Mothers

Abstract

This study was designed to evaluate free amino acid (FAA) composition and total protein in mature human milk from Turkish mothers. Free amino acid concentrations in mature human milk were determined in all subjects using a high‐performance liquid chromatography (HPLC) with postcolumn derivatization system, with a fluorescence detector. Total protein content was determined by the classical biuret method. Total protein concentration was found to be 1.3±0.4 mg/dl. Glutamic asid plus glutamine is the most abundant amino acid (1275 µmol/L), followed by taurine (353 µmol/L) and alanine (261 µmol/L). Glutamic acid plus glutamine accounts for the most free amino acids in mature human milk and their sum represents 40% of total FAA. On the other hand, some amino acid derivatives such as citrulline, ethanolamine, ammonium, ornithine, ortophosphoserine, and phosphoethanolamine, not usually a part of protein, are determined and this fraction represented ∼21% of the total FAA in mature human milk in the present study.

Keywords:

• Human milk
• protein
• amino acids
• free amino acids
• essential amino acids
• HPLC
• postcolumn derivatization