Method for Removing Thawed Human Milk From a Plastic Storage Bag Impacts Fat Retention.

Objectives: Determine how thaw stage and bag manipulation (folding and squeezing) influence the retention of fat and number of aerobic bacteria colony-forming units when decanting human milk (HM) from plastic storage bags.

Methods: Lactating women (n = 40) in the Greensboro, North Carolina area were recruited to provide fresh HM. Samples were equally divided and frozen in storage bags for 2 months. Two thaw stages (ice/liquid) and the use of bag manipulation (yes/no) were assessed. Fat was measured using ether extraction and bacteria were measured using plate enumeration. Paired t tests were used to compare the effects of thaw stage and bag manipulation on post-thaw fat content. Repeated measures analysis of variance was used to compare the effect of bag manipulation on pre- and post-thaw bacteria.

Results: Fat retention was not significantly different when thawing to liquid versus ice (mean difference = 0.10 g/dL; n = 17 paired samples; P = 0.07). Decanting with bag manipulation retained more fat than decanting without manipulation, but only when HM was thawed to liquid (mean difference = 0.13 g/dL; n = 11 paired samples; P = 0.005), not when HM was thawed to ice (P = 0.47). Bag manipulation did not increase total aerobic bacteria for either thaw stage (P = 0.49).

Conclusions: Fat retention is influenced by the method of removing previously frozen HM from plastic storage bags. Folding and squeezing the storage bag when decanting HM thawed to a liquid state increases fat recovery without increasing bacterial contamination.