Lipases are a helpful, natural part of breastmilk — they help babies digest the fats in their mothers’ milk (see my last post). When babies are drinking milk at the breast this is always a good thing. Sometimes, though, when mothers are pumping milk for their babies to drink later, lipases can be too much help. Some mothers with high lipase activity in their milk find that their milk tastes “soapy”, “rancid”, or “sour” after storing it for a while. This happens even when the milk is cooled and stored according to current safe storage guidelines. It can be pretty frustrating for the baby (who doesn’t like icky milk) and the mother (who is trying to feed her baby well while they’re separated) and the caregiver (who has to take care of a sad baby).
Fortunately lipase can be inactivated by heating milk before storing it. Some mothers find that they don’t have to scald their milk if they don’t store it for very long before feeding it to baby. To read more about figuring out how long you can store your milk and ways to scald it, you can check out this thread on the LLLI mother-to-mother forums.
Thank goodness this is a rare problem — otherwise many more mothers would find it even more challenging to combine working and breastfeeding.