Does thawing and warming affect the integrity of human milk?

Abstract

ObjectiveAs most neonates in the NICU are fed defrosted human milk (HM), we evaluated the integrity of the HM after freezer storage, thawing, warming, and waiting to be fed.MethodsNICU mothers (n=41) donated 100 ml of milk. Baseline aliquot was stored at −80°C, and the remaining milk was stored 7 days at −20°C. Subsequently, milk was thawed and warmed using tepid water or waterless warmer. A separate sample of thawed milk was maintained in refrigerator for 24 h and warmed. Warmed milk was maintained at room temperature (RT) for 4 h. Milk integrity was described as the effect on pH, protein, sIgA, lactoferrin, and bacterial colony counts (total, TBCC; Gram positive, GPCC; Gram negative, GNCC). Data analyzed by ANOVA and paired t test.ResultsThere were no differences in milk integrity between the two warming methods. There were no changes in protein, sIgA, and lactoferrin with processing. There was a significant change in pH between baseline, thawing, and warming, p < 0.001. When thawed milk was warmed after refrigeration, there was a further decline in pH. TBCC, GPCC, GNCC did not change significantly with processing but when warmed milk was maintained at RT all counts increased, p < 0.01.ConclusionThawing and warming do not change the integrity of previously frozen human milk adversely. The integrity of the milk is affected similarly by the two methods. Concerns about maintaining warmed milk at RT need to be explored.