New insights into the alterations of full spectrum amino acids in human colostrum and mature milk between different domains based on metabolomics

Amino acids (AAs) in milk constitute proteins, not only that, they also play a significant part in the body. However, in-depth analysis of AAs in human milk between different lactation periods and different domains is relatively scarce. Herein, free AAs in human colostrum (FHC) and mature milk (FHM), and insoluble-proteome AAs in human colostrum (IPHC) and mature milk (IPHM) were characterized, using metabolomics method based on iTRAQ combined with HPLC–MS/MS. A total of 35, 35, 30, and 30 AAs were characterized in FHC, FHM, IPHC, and IPHM, respectively. Moreover, 20 and 13 significantly differential amino acids (SDAAs) were identified in FHC vs. FHM group and IPHC vs. IPHM group, respectively. The interaction network of these SDAAs was further analyzed, and the SDAAs of these two groups were found to participate in 31 and 24 differential metabolic pathways, respectively. The profiles of free and insoluble-proteome AAs between human colostrum and mature milk were quite different, and the combination of these AAs could offer a better understanding of the changes in biochemical process in human milk, and could also furnish directions for the research into development of babies nutrition and milk powder.