The immunoprotective constituents of human milk are stable when stored at room temperature for 8 hours, when stored at 0 degree-4 degrees C for three days, or when frozen at -20 degrees C for 12 months. They are also stable during pasteurization at 56 degrees C for 30 minutes. Sonification may reduce levels of sIgA and lysozyme and the ability of milk to inhibit growth of E coli. The number of cells in human milk is reduced by storage, freezing, pasteurizing, microwaving and sonification, and the functional capacity of surviving cells is also reduced.