Breastfeeding 108 – Why does refrigerated breast milk smells sour

When you thaw or warm your frozen and refrigerated milk, you might find t he milk smelling sour. If you followed the rules and guidelines to safely store breast milk, then this information might help you to feel a little bit at ease.

I faced this problem during the breastfeeding of both of my babies. Apparently, this common issue is cause by an enzyme in the milk called lipase, which aids in the digestion of fats. Lipase begins to break down the fat in stored breast milk during warming cause this smell. It doesn’t pose any hazard except for your baby rejecting the stored milk due to its sour smell.

There are 2 ways for prevent this smell:

1. After expressing the milk, bring it to a quick scald and quickly cool it down before storing. This prevents the smell when reheating the milk.
2. When you take the frozen milk out of the freezer, thaw it out in the refrigerator for a day instead of heating right ahead. Warming the milk in a double boiler might help prevent the smell.

Other sources:
Storage and Handling of Breastmilk
My expressed breastmilk doesn’t smell fresh. What can I do?
Breastfeeding Series:
Breastfeeding 101 – Amazing Mother’s Milk
Breastfeeding 102 – First experience after birth
Breastfeeding 103 – Tips for correct breastfeeding techniques
Breastfeeding 104 – Comfortable and healthy nursing positions
Breastfeeding 105 – Increasing mother’s milk supply
Breastfeeding 106 – Troubleshooting for nursing problem
Breastfeeding 107 – Storing breast milk
Breastfeeding 108 – Why does refrigerated breast milk smells sour
Breastfeeding – Other questions