Milk Bank Pooling Practices Impact Concentrations and Variability of Bioactive Components of Donor Human Milk

Background: Donor human milk (DHM) bank practices, such as pasteurization and pooling according to postpartum age of milk donations and number of donors included in a pool may impact the resulting concentration of bioactive components of DHM. Aims: We determined the impact of Holder pasteurization, postpartum milk age, and pool donor number (number of donors included in a pool) on resulting concentrations of total immunoglobulin A (IgA; which provides immune protection to the recipient infant) and insulin (an important hormone for gut maturation).We also documented inter-relationships between these bioactive components and macronutrients in DHM pools. Methods: Pre and post-pasteurization aliquots of 128 DHM samples were obtained from the Rocky Mountain Children's Foundation Mother's Milk Bank (a member of the Human Milk Banking Association of North America, HMBANA). Macronutrients were measured via mid-infrared spectroscopy. Total IgA was measured via customized immunoassay in skim milk and insulin was measured via chemiluminescent immunoassay. Results: Mean post-pasteurization total IgA concentration was 0.23 ± 0.10 (range: 0.04-0.65) mg/mL a 17.9% decrease due to pasteurization (n = 126). Mean post-pasteurization DHM insulin concentration was 7.0 ± 4.6 (range: 3-40) μU/mL, a decrease of 13.6% due to pasteurization (n = 128). The average DHM pool postpartum milk age was not associated with total IgA or insulin concentrations, but pool donor number was associated with bioactive components. Pools with only one donor had lower total IgA and lower insulin concentrations than pools with at least 2 donors (p < 0.05). Increasing the number of donors in a pool decreased the variability in total IgA and insulin concentrations (p < 0.04). Conclusion: Increasing the number of donors included in DHM pools may help optimize bioactive components in DHM received by premature infants. These results help inform milk banking practices to decrease compositional variability in produced DHM pools.

Effect of Pooling Practices and Time Postpartum of Milk Donations on the Energy, Macronutrient, and Zinc Concentrations of Resultant Donor Human Milk Pools

OBJECTIVE

To characterize the macronutrient, energy, and zinc composition of pasteurized donor human milk pools and evaluate how composition varies based on pooling practices and "time postpartum" (ie, elapsed time from parturition to expression date) of individual milk donations.

STUDY DESIGN

The Mothers' Milk Bank (Arvada, Colorado) donated 128 donor human milk pools. Caloric density was assessed via mid-infrared spectroscopy, and zinc concentration was measured by atomic absorption spectroscopy. Pool time postpartum was calculated as the unweighted average of the time postpartum of all milk donations included in any given pool.

RESULTS

Time postpartum of donor human milk pools ranged from 3 days to 9.8 months. The majority (91%) of donor human milk pools included milk from either 1 donor or 2 donors. Pool energy density ranged from 14.7 to 23.1 kcal/oz, and protein ranged from 0.52 to 1.43 g/dL. Milk zinc concentrations were higher in preterm pools and were negatively correlated with pool time postpartum. We present an equation that estimates donor human milk pool zinc content based on time postpartum and explains 49% of the variability in zinc concentrations (P < .0001). Including more donors in donor human milk pools decreased the variability in protein, but not zinc, concentrations.

CONCLUSIONS

Donor human milk pools were lower in calories than is normally assumed in standard human milk fortification practices. Zinc concentrations were related to donor human milk time postpartum and were on average insufficient to meet preterm and term infants' needs without fortification or supplementation.