Storage of Unfed and Leftover Pasteurized Human Milk

Objective: To determine the impact of storage on bacterial growth and immunological activity of pasteurized human milk and leftover pasteurized human milk that has been exposed to the microflora in an infant's mouth. Materials and Methods: Eighteen mother-infant dyads participated in two separate studies. Mother's milk was pasteurized, and each baby was fed 1 to 2 ounces. Pasteurized and leftover pasteurized milk were stored at room (24 degrees C) and refrigerated temperatures (4 degrees C). After storage, milk was analyzed for bacteria, total protein, lysozyme activity, and secretory immunoglobulin A (SIgA) activity. Results: In pasteurized and leftover pasteurized milk stored in the refrigerator for 7 days, total aerobic bacteria do not increase significantly and total protein and bioactive proteins are stable. At room temperature, there is a significant increase in total aerobic bacteria in leftover pasteurized milk during 12 hours of storage (p<0.01) and a significant decrease in total protein and SIgA activity in pasteurized milk during 12 hours of storage (p=0.02 and p=0.03, respectively). Conclusions: When stored in the refrigerator, pasteurized and leftover pasteurized milk may be stored for at least 7 days when considering the variables studied. Caution should be used when storing pasteurized and leftover pasteurized milk at room temperature to prevent an increase in bacterial growth and a decrease in total protein and SIgA activity.