The freeze-drying does not influence the proteomic profiles of human milk

Purpose: Human milk (HM) proteins are known as important factors in growing and development of neonates. For longer and easier storage of HM, freeze-drying is suggested as one of the promising methods for HM banks. However, the effects of freeze-drying on HM proteins were not evaluated yet. The purpose of this study is to analyze and compare proteomic data before and after the freeze-drying.Material and methods: Totally nine fresh HM samples were collected from three healthy mothers at 15 and 60 days of lactation period. The samples were freeze-dried and the proteomic analysis was performed by shotgun proteomic method with mass spectrometry. The results were compared between samples of different lactation periods, and before and after the freeze-drying using Wilcoxon signed-rank test for paired comparisons. Moreover, the functional grouping and analysis were performed for the detected proteins by bioinformatics analysis.Results: Totally, 245 proteins were detected in the HM samples. The expression of proteins was not affected by both of the different lactation periods and the freeze-drying status (P>.050). Moreover, the functional analysis of proteomic data revealed no significant difference between both groups as well.Conclusion: HM proteins were found not to be significantly affected by the lactation periods (15 and 60 days) and freeze-drying status. As significant changes of HM proteins were not found after the freeze-drying, we hope that the present study would support introducing freeze-drying in the HM banks. However, the number of samples was quite small to provide strong evidence. Moreover, the evaluation of the safe storage length in the view of infectious agents and the composition changes after freeze-drying is warranted in the further study.