Some babies reject refrigerated or frozen milk because of high lipase activity, which can cause a metallic taste or smell. If your baby refuses the milk, try offering it at room temperature rather than warmed, or try mixing fresh milk with stored milk in an 80:20 ratio, gradually increasing the stored portion. To minimize the development of lipase, store milk in the fridge for no more than 48 hours and avoid long-term freezer storage if possible.