Effect of storage on the creamatocrit and total energy content of human milk.

Human milk samples were collected from mothers on the third post-partum day with a manual breast-pump and pooled. They were divided into aliquots and stored at room temperature (24-25 degrees C), and at 4 degrees, 37 degrees and -20 degrees C. The creamatocrit (CR) values decreased significantly after storage at room temperature (P less than 0.03), or at 37 degrees C (P less than 0.001) for 45 min and 30 min, respectively. Creamatocrit remained stable for 14 d at 4 degrees C, and for up to 28 d at -20 degrees C. However, freezing and thawing samples twice significantly decreased creamatocrit values (P less than 0.001). The total energy concentration of the samples stored at -20 degrees C was stable for 28 d. These results indicate that strict precautions must be taken when handling and storing human milk samples for analysis of lipid content.