Microbiota composition of human milk based on storage and processing methods in Korea

BACKGROUND/OBJECTIVES: The microbiota present in human milk (HM) plays a crucial role in infant health and development. Maintaining it during storage and thawing is vital for preserving its beneficial properties; however, the effects of storage period, temperature, and thawing conditions on HM are not well understood. SUBJECTS/METHODS: HM samples from lactating mothers were collected and stored under different temperature conditions (room temperature [RT], refrigeration, and -20°C) for different durations (1 week and 4 weeks), and thawed using different methods (RT, bottle warmer, and microwave), followed by analysis of their microbiota. RESULTS: Storing HM samples at RT for a week and at -20°C for four weeks resulted in a significant reduction in microbiota diversity, whereas the other treatments did not lead to a significant change in beta diversity. In the microbiota distance analysis, HM samples stored at -20°C for a week showed the highest similarity to the initial microbiota compared to those after one week of storage at RT or in a refrigerator. Microwave thawing after 1 week of freezing resulted in the greatest alteration in the initial microbiota composition, whereas thawing at RT or with a bottle warmer showed comparable microbial profiles. CONCLUSION: The most suitable method for storing and thawing HM while preserving the microbiota is to store it at -20°C for up to one week and thaw it using a bottle warmer.