Alterations in the host defense properties of human milk following prolonged storage or pasteurization.

Objectives:Preterminfantsareoftenfedpasteurizeddonormilkormother’s milk that has been stored frozen for up to 4 weeks. Our objectives were to assess the impact of pasteurization or prolonged storage at � 208C on the immunologic components of human milk and the capability of the different forms of human milk to support bacterial proliferation. Materials and Methods: The concentrations and activities of major host defense proteins in the whey fractions of mother’s milk stored for 4 weeks at � 208C or pasteurized human donor milk were compared with freshly expressed human milk. Proliferation of bacteria incubated in the 3 forms of human milk was assessed. Results: Relative to freshly expressed human milk, the concentrations of lysozyme, lactoferrin, lactoperoxidase, and secretory immunoglobulin A were reduced 50% to 82% in pasteurized donor milk and the activities of lysozyme and lactoperoxidase were 74% to 88% lower (P <0.01). Proliferation of bacterial pathogens in pasteurized donor milk was enhanced 1.8- to 4.6-fold compared with fresh or frozen human milk (P <0.01). Conclusions: The immunomodulatory proteins in human milk are reduced by pasteurization and, to a lesser extent, by frozen storage, resulting in decreased antibacterial capability. Stringent procedureto minimize bacterial contamination is essential during handling of pasteurized milk.