Why does My Breast Milk Smell Sour?

Queue the “yuck” factor! There are instances where a pumping mom follows all breast milk storage guidelines only to find that their milk smells soured and has a metallic or soapy taste.

It can be very disheartening to think of having to toss that milk out. If this is you, don’t pour that milk down the drain just yet!

In most cases, this is a simple matter of excess lipase.

What is Lipase?

Lipase is an enzyme responsible for the breakdown of fats to fatty acids. It is an important component in breast milk that helps break down the milk fats so it is more easily digested by a baby. It is thought that high levels of lipase in a mother’s milk might contribute to the sour smell of refrigerated or frozen milk.introducing-bottle-to-breastfed-baby

An easy test to ensure the issue is not storage related (failed freezer, etc), place a few ounces of breast milk in two storage containers and store in one in the refrigerator and the other in the freezer for a few days.

If the milk still smells off, then you likely have a high lipase issue on your hands.

Despite the change in smell or even taste, if proper storage guidelines were followed, the milk is safe to use. Most babies don’t mind the change and will still drink it without complaint.

What if Baby Refuses Milk?

There are instances where a baby may not prefer the taste of the milk but don’t fret, there is a way to prevent the soured smell and taste of the breast milk.

  1. scalding-breast-milkPump freshly expressed milk
  2. Immediately heat fresh milk in a small pot over low heat on the stove
  3. Scald the milk- that means to heat until tiny bubbles form around the edges (approx 180 degrees)
  4. Remove the milk from the stove and quickly chill it
  5. After milk is chilled, freeze the milk if desired

Note, that scalding breast milk does reduce some of the “good things” in the milk so its best to serve fresh milk whenever possible.

Learn More About Excess Lipase and Get Tips on Scalding Breastmilk including How to Use a Bottle Warmer to Scald Breastmilk -HERE!

Are you facing this issue? Reach out with any questions or comments by leaving your remarks on this page. We would love to hear from you!

Also See –


Read: Sore Nipples and Breastfeeding – 6 Must-Have Products to Soothe Sore Nipples


Read: Find Avent Bottles and Accessories here!


Read: Introducing Bottle to a Breastfed Baby

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