According to National Health and Medical Research Council expressed breast milk can be stored:
Always use the oldest milk first when it’s time to feed baby.
Milk can be fed at room temperature, but your baby may prefer it heated (after all, it comes from the source at body temperature).
You can thaw frozen milk by setting it in a bowl of hot tap water (not boiling) or by holding it under running warm water.
Never use a microwave to heat baby milk (it can not only cause hot spots that could burn your baby, but will destroy some of the beneficial components of breastmilk).
Milk that has been previously frozen cannot be frozen again and must be discarded.
Once breast milk is thawed it can be refrigerated for a maximum of 24 hours or left at room temperature for a maximum of 4 hours.
There are a number of options when it comes to storing breast milk. They include:
It is important to label the date when you freeze your milk so you don't let it go off. Also labelling the time you expressed is handy as if you need to top your baby up with milk, you can use milk from a similar time of day.
It's best to try and split the milk up into smaller portions so you can easily vary the quantity to what your baby needs. Also smaller portion sizes will defrost quicker and easier than a bigger portion sizes.