Bacterial Content of Raw and Processed Human Milk ¹

Mature human milk samples were manually expressed into sterile containers and examined for their bacterial content. No other special precautions were taken to ensure asepsis. The total counts of seven individual samples ranged from 1.5 × 10³ to 1.9 × 10⁷ CFU/ml; the counts of pooled samples used for further processing ranged from 4.2 × 10⁶ to 5.7 × 10⁷ CFU/ml. Freezing had no significant effect on the counts. Although freeze-drying reduced the mean count by one log cycle, the decrease was not significant and the level of contamination was above the level considered safe for human consumption. Pasteurization at 62.5°C for 30 min reduced the load 4-5 log cycles and the reduction continued during subsequent storage at -25°C. Although heating at 75°C for 15 min reduced the load 6-7 log cycles, the microbial counts tended to increase during subsequent storage at 4°C.