Dr. Lawrence has answered many of your questions on pumping and storing breastmilk. She was one of eight doctors who helped the American Academy of Pediatrics draft its 1997 policy statement supporting breastfeeding. The answer is modified. We recommend that you chill the milk for an hour or two before putting it into the freezer. I suggest limiting the amount of time that the milk is in the refrigerator before putting it in the freezer to about six hours maximum.
Refrigeration slows down the enzyme activity, but it doesn t halt it.
Milk also tends to separate in the fridge, so you have a fat layer and a milk layer. Therefore, when you put milk in the freezer earlier, it is of better quality. When it is in the refrigerator too long, bacteria can grow. Freezing the milk halts the growth of bacteria, but it doesn t kill them. If plastic is used, you want something that you can fill without difficulty, and that you can store upright and open easily without spilling and risking bacteria getting in the milk.