Digging into Human Milk Oligosaccharides by Milk Pasteurization and Freeze-Dry

Human breast milk is frequently heated or frozen to restrain microbial growth. Nutrient compounds consisting of carbohydrates, proteins, and lipids are often affected by heating and freezing steps. In this study, we have monitored the change of human milk oligosaccharides (HMOs) after pasteurization and freeze-drying steps. HMOs are a family of structurally diverse unconjugated glycans that are highly abundant in human milk. It is well known that various structures of HMOs are associated with absorption, catabolism and biological functions such that contribute to immune maturation, organ development, and health microbial colonization. However, there is no previous study regarding chemical stability of HMOs during high temperature pasteurization and freeze-dried. Briefly, human milk samples from 3 mothers were pasteurized at 63℃ for 30minutes and freeze-dried at-83℃ for 5days, respectively. HMOs were enriched and profiled by mass spectrometry. Initially the composition and structure of HMOs was assigned by MALDI-TOF/TOF MS. Further, native HMOs were relatively quantified by PGC column-based LC/MS providing an enhanced separation of isomeric structure. More than 30 HMOs have been identified and quantified. We could confirm that pasteurization and freeze-drying of human milk does not influence chemical property of HMOs at all.