Frozen Breastmilk Turning Sour


My baby refuses to eat my frozen breastmilk. I store my expressed milk in the fridge immediately and I freeze it within 48 hours. I use a chest freezer. I store it in the lansinoh storage bags. I've thawed the frozen milk in the fridge and in warm water. As soon as its completely liquid, I warm it up in a bowl of warm water and try feeding it as soon as my baby is hungry. However, I notice right away that it smells horrible and my baby won't eat it. What am I doing wrong? By the way, I've tried thawing milk that's been frozen anywhere from a week to 3 months. If you could please give me an answer I would really appreciate it.


It could be that you have an excess of the enzyme lipase in your milk, which begins to break down the milk fat soon after the milk is expressed. Most babies do not mind a mild change in taste, and the milk is not harmful, but the stronger the taste the more likely that baby will reject it.
Lipase is an enzyme that is normally present in human milk and helps keep milk fat well-mixed whey portion of the milk, and also keeps fat globules small so that they are easily digestible.
Once the milk becomes sour or rancid smelling/tasting, there is no known way to salvage it. However, newly expressed milk can be stored by heating the milk to a scald to inactivate the lipase and stop the process of fat digestion. Scald the milk as soon after expression as possible.
To scald milk:
◾Heat milk to about 180 F (82 C), or until you see little bubbles around the edge of the pan (not to a full, rolling boil).
◾Quickly cool and store the milk.

Scalding the milk will destroy some of the anti-infective properties of the milk and may lower some nutrient levels, but this is not likely to be an issue unless all of the milk that baby is receiving has been heat-treated.

If your milk tastes/smells sour or rancid rather than soapy, the cause may be chemical oxidation rather than lipase. It could be related to any intake of polyunsaturated fats that you have ingested yourself or free copper or iron ions in your water. When this happens, here are a few suggestions to try:
◾avoid your usual drinking water (either drinking it or having milk come into contact with it)
◾avoid fish-oil and flaxseed supplements, and foods like anchovies that contain rancid fats
◾increase your antioxidant intake (including beta carotene and vitamin E).
Sources:;; Lawrence & Lawrence, Breastfeeding for the Medical Professional

Kindest Regards,

Gina Ciagne, CLC

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