367 - Temporal Changes in pH and Osmolality of Fortified Human Milk

Preparations of human milk at increased fortification densities above 24 kcal/oz are used to optimize growth and generally clinically tolerated. Fortified human milk may be fed up to 24 hours after preparation. It is unknown how these non-standard higher caloric recipes and newer human milk fortifiers (HMF) affect the osmolality and pH of human milk or how these properties are altered temporally.

Objective:

To evaluate the pH and osmolality of fortified human milk over a 24-hour period after preparation using standard and increased fortification recipes.

Design/Methods:

Frozen unpasteurized human milk was used as the base. HMF agents utilized were Similac (SHMF; extensively hydrolyzed bovine milk casein), Enfamil (EHMF; partially hydrolyzed bovine milk whey; high protein (HP) and standard protein), Prolacta (human milk-based). Recipes were prepared in 2 kcal/oz increments, up to 26 kcal/oz for SHMF and up to 30 kcal/oz for the others (Table 1). SHMF was also prepared with the addition of liquid protein (LP). For each recipe, pH and osmolality were tested at 0, 12, and 24 hours after preparation and refrigeration at 4 degrees Celsius. Group differences were analyzed using t-test (between HMFs) and paired t-test (temporal comparisons).

Results:

9 of 21 preparations have been tested to date. pH decreased and osmolality increased with higher caloric densities with both SHMF and EHMF-HP. At time 0, mean pH lower with EHMF-HP than SHMF (5.97 ± 0.26 vs. 6.38 ± 0.16, p=0.038), but this difference did not persist to 12 and 24 hours (Table 2). Osmolality was higher for SHMF than EHMF-HP at all time points (Table 3). Compared to 0 hours, SHMF recipes had observable changes in pH (p< 0.01) and osmolality (p=0.01) by both 12 and 24 hours, but the percentage change in pH and osmolality at 12 vs. 24 hours did not reach statistical significance.

Conclusion(s):

Commercially available HMF products decrease the pH and increase the osmolality of human milk but to varying degrees. Temporal changes differ by manufacturer, likely secondary to ingredient source, distribution of nutrients, and breakdown by bioactive components within human milk. Additional testing will include EHMF-SP and Prolacta, as well as fresh human milk and pasteurized donor milk.