The Effects of Refrigerated Storage of Donor Human Milk with Limited Bacterial Presence After Holder Pasteurization on Nutrient Concentration and Bacterial Growth.

Background: The Human Milk Banking Association of North America (HMBANA) sets the purity and quality standards for donor human milk (DHM) in the United States, which includes zero bacterial presence after Holder pasteurization. This study aimed to determine if nutrient and bacterial composition of DHM with limited bacterial presence after pasteurization change over 4 days of refrigerated storage. Methods: Twenty-five unique samples of DHM with limited bacterial growth postpasteurization were collected from two HMBANA milk banks. Infant formula was used as a comparison. Samples were stored in the refrigerator and a portion of milk was removed at 24-hour intervals beginning at hour 0 to 96 for analysis. Aerobic bacteria, protein, lactose, and immunoglobulin A (IgA) content were measured. Longitudinal changes between 0 and 96 hours were analyzed using repeated measures analysis of variance and mixed models test. p  < 0.05 was deemed significant. Results: There was no significant difference in lactose, protein, bacteria, or IgA content over storage duration ( p  = 0.649, p  = 0.690, and p  = 0.385, p  = 0.805, respectively). Total aerobic bacteria were less than 10 2 colony-forming units (CFUs) in 81% of the time points tested for DHM samples. Total aerobic bacteria were too many to count (>300 CFUs) in the infant formula sample at all time points. Conclusion: In periods of high demand for DHM, DHM with low bacteria growth postpasteurization may be an option as a supplemental food for the growing number of healthy infants who receive DHM. Future studies should investigate the bacterial strains in this milk.