It’s true that even after you’ve properly stored your milk (and sometimes even before you store it) your breast milk can go sour. It may taste and/or smell sour, metallic or simply rancid. It is not a typical problem but it does happen occasionally: too much lipase.
Lipase is an enzyme that breaks down fat. Fat however, it what makes breast milk taste good. Fat actually makes lots of foods taste good for that matter, but I’m getting off topic here. Essentially the lipase is “eating up” all the fat in mom’s breast milk and the result is sour tasting milk. While it is more common when a mom tries to store breast milk, it can happen before milk ever leaves the breast–especially if your baby is particular with his tastes.
If you have too much lipase in your breast milk, you can still breastfeed! Here is what you should do:
Once the milk becomes sour there is no way to salvage it. If your stored milk is sour you should toss it out. However, newly expressed milk can be stored by first scalding the milk. Scalding the milk inactivates the enzyme so it stops the process of fat digestion.
To scald milk:
*Heat expressed milk to about 180 degrees F, or until you see little bubbles around the edge of the pan. Do NOT heat it to a full rolling boil.
*Quickly cool and store milk.
Scalding the milk will in fact destroy some of the beneficial properties of your breast milk but not all of them and it still retains enough properties to be more beneficial than formula.
How do you know if you have too much lipase? If your milk seems to spoil quickly, or tastes and smells sour. . .too much lipase is probably the culprit. However, breast milk can also seem sour to your baby if you breastfeed right after you’ve exercised. A good test for too much lipase is to go ahead and scald some expressed milk. After it has cooled, you can see if it still has the sourness. If not, you’ve probably solved the problem!
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