What To Do If Your Fresh Frozen Milk Smells or Tastes Bad

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You just thawed a bag of frozen milk, and it smells! Even though you froze it when it was fresh! Is the milk spoiled? Probably not. This post explains what’s going on, and if it is safe to give this milk to baby.

You can usually tell if fresh breast milk has spoiled by smelling it, but with frozen breast milk, the sniff test isn’t always reliable. Sometimes fresh frozen milk smells bad!

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If your properly stored frozen milk has a funky taste or odor when you thaw it out, don’t freak out just yet. Your milk is probably not spoiled! But you might be dealing with one of two issues:

1) High Lipase Milk

The fat molecules in your milk are surrounded by a membrane. The purpose of this membrane is to keep out lipase, an enzyme in milk that helps baby break down (digest) milk fat molecules.

When you freeze breast milk, this protective membrane gets destroyed and lipase is free to break down all the fat molecules it can. If you have high lipase milk, this can cause your milk to have a soapy or sweaty taste.

Not everyone has high lipase milk. But if you do, have no fear! It’s 100% safe for baby to drink your thawed, frozen milk. In fact, most babies will be perfectly happy to drink it, so don’t be afraid to offer it.

Diagram that explains how the enzyme lipase can make frozen breastmilk smell bad.

2) Chemical Oxidation

If your milk has a fishy or metallic taste, you might be dealing with something called chemical oxidation. We don’t know a lot about this phenomenon, but we think that it happens when oxygen molecules interact with naturally occurring polyunsaturated fatty acids in your milk. Oxidation of fatty acids in milk can be influenced by milk storage time, thawing temperatures, and potentially even exposure to light.

This milk is also 100% safe for baby to drink—it is not spoiled. However, some babies may refuse to drink it. 

Frozen breastmilk in the freezer
Never throw away frozen milk that baby won’t drink! Consider offering it up for donation instead! If a milk bank won’t take it, consider privately donating.

What can be done?

If your milk has a soapy/sweaty taste and your baby refuses to drink it, you might consider scalding your milk BEFORE you freeze it. Scalding must be done beforehand: Scalding milk after it has already been frozen won’t help.

To scald milk, you want to heat it just until it starts bubbling around the edges. You don’t want to boil it. This gentle heating deactivates the lipase in the milk.

Scalding breastmilk on the stove before freezing it can help with high lipase milk that smells funny
Lightly heating the milk in this manner deactivates the lipase in the milk, which can help eliminate the soapy tastes frozen breastmilk sometimes has.

Scalding should ONLY be done if baby refuses to drink your frozen milk. This is because scalding destroys a small amount of the milk’s beneficial properties. If baby is happy to drink your frozen milk despite the taste/smell, you don’t need to (and shouldn’t) take the time to scald it. According to experts, scalded milk is still preferable to formula, so don’t be afraid to scald your milk if that’s what it takes to get baby to drink it.

If you scald your fresh milk, freeze it, and still find that it has a fishy or metallic taste when you thaw it out, then you’re probably dealing with chemical oxidation instead of high lipase milk.

To reduce tastes and odors caused by oxidation, experts recommend freezing your fresh milk immediately, trying to keep the milk away from light exposure, and reducing polyunsaturated fats in your diet (things like salmon, vegetable oils, and some nuts and seeds are high in polyunsaturated fats). Some suggest adding small amounts of non-alcoholic natural vanilla flavor to your milk, but this has not been tested and might not be a good idea.

Always thaw frozen breastmilk under running water, in a bowl of warm water, or in the fridge.
Always thaw frozen breastmilk by running it under warm water (putting it in a bowl of warm water works too) or by placing it in the fridge to thaw. Frozen milk thawed in the fridge is good in the fridge for 24 hours and for 4 hours at room temperature.

A few reminders:

Sometimes thawed frozen milk smells or tastes bad. A soapy, sweaty, fishy, or metallic taste can be normal, if a bit unappetizing. Rest assured that this milk isn’t spoiled, especially if you are confident that your milk has been handled and stored properly.

Always be sure to freeze your milk in clean/sterilized bags or containers that are designed to safely store human milk (Ziploc brand style baggies are not recommended—they are not sterilized and are too thin to protect nutrients in the milk from freezing temperatures). And when thawing frozen milk, remember to never microwave it. Instead, thaw it in the fridge or under warm running water.

And lastly, if your baby just isn’t having your frozen milk, don’t toss it just yet! Join a breastfeeding support group or milk share group in your area (Facebook probably has a few) and see if there is a breastfeeding parent in need of donor milk. You can also save the milk to put in baby’s bath—it’s good for the skin!

Boost Your Milk Supply & Keep It Up

Our FREE guide will give you 5 simple, proven tips to boost your milk supply and increase your pump output. Get results in as little as just a couple days!

If you enjoyed this post, be sure to check out our digital library of helpful resources that quickly teach how to avoid common breastfeeding problems and give you the peace of mind and confidence you need to meet your breastfeeding goals.

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