How to freeze breast milk?

The French Food Safety Agency (AFSSA) recommends not keeping frozen milk for more than 4 months in the freezer. You can keep it for up to a maximum of 12 months in a chest freezer, provided it was expressed with great care, the baby is in good health, and it is not a newborn.

The storage duration will then be between 2 and 3 months.

The freezing period will then be a maximum of two weeks

Milk expressed by some mums can take on a different taste and smell after collection. This smell can be even more pronounced after freezing. Enzymes in breast milk pre-digest its main sugar, lactose, giving it this rancid smell. The nutritional benefits of the milk remain unchanged, but some babies may refuse it due to the change in taste.

To avoid the heartbreak of having to throw away your hard-earned milk reserves, it is advisable to test a sample before freezing a larger quantity.

Are you planning to build up a stock of frozen milk? Do a first test before storing more:

– First freeze a small amount and wait a few days. If the smell remains unchanged, you can freeze more.
– If the smell is different (such as soapy), offer the milk to your baby after warming it. If they accept it without any problem, you can continue to freeze it.

If your baby no longer accepts the milk, it is recommended to heat your freshly expressed milk to 50–60 degrees for 5 minutes (wait for a gentle shimmer around the edges of the saucepan), then place it in the fridge to cool quickly before freezing. Heating destroys the lipases responsible for the change in smell.  

Another explanation for the rancid smell could indeed be the occurrence of chemical oxidation. Oxidation is a chemical reaction involving an exchange of electrons between substances. This could be due to something present in your drinking water, such as free copper or iron ions (positively or negatively charged atoms or molecules), or to certain polyunsaturated fats in your diet.

It is preferable to store your milk in small quantities (less than 120 ml, or the equivalent of one bottle), so as to limit waste and to be able to defrost exactly the amount you need. Once defrosted, milk cannot be refrozen and must be used within a maximum of 24 hours. You can also freeze different volumes (60, 100, 120 ml for example).

 If you are using a breast pump to build up a supply ahead of your return to work and plan to express your milk, freeze the quantity needed for the first day's bottles. On the second day, your baby's bottles will be prepared with the milk you expressed the day before.

 It is however always useful to have a little extra in reserve, in case of an unplanned absence or outing, or if you notice a dip in your milk supply. The equivalent of 2 or 3 days' worth of bottles makes an excellent reserve.

It seems that glass (ideally tinted) or a breast milk storage bag BPA-free (Bisphenol A) option are a good choice. The latter are easy to use and take up little space in the freezer if you freeze them flat. 

White blood cells may be better preserved when milk is stored in plastic. If you choose plastic containers, make sure they are also BPA-free. Remember to remove the air before sealing the bag, for better preservation.

In all cases, the chosen container must be washed beforehand and must be able to be sealed hermetically!