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Handling Milk: Top Tips for Freezing, Thawing, Re-Heating, and Using Milk

Hand reaching into freezer full of milk storage bags and containers of milk.

Freezing and reheating milk should be a no-brainer, right? Well, no, it’s a little more complicated. There are many questions and myths floating around about what to do and what not to do. Here I’ve summarized my top tips for handling milk.

Myths and leftovers

I can’t count how many times I’ve been asked these questions.

  • “How long can the milk stay out at room temperature?”
  • “Can the milk be re-frozen after it has been thawed?”

These and similar questions are motivated by the desire to conserve the leftover milk.

All those worries could be avoided by doing one simple thing: Avoid having any leftovers.

Thaw only the amount the baby will consume. Here’s how.

Freeze the milk in smaller portions

Freeze the milk in ice cube trays. Each cube contains about 1 ounce (about 30 ml) of milk. I call these “second helpings.”

Rather than opening a completely new bag or bottle when the baby is a little hungrier than usual, this is an easy way to give provide more milk without creating more waste.

Ignore the myths

  • “The ice cube trays need to be covered.” There’s no truth to that. However, you could slide it inside of a big plastic bag if you wish.
  • “The plastic is dangerous because of the BPA.” Nope. There are four basic types of plastic; only one main type has BPA. That type is not used to make ice cube trays.
  • “The AAP forbids this.” Nope, no truth to that, either.

Special techniques for storing and using

Here are some tips about the techniques for handling milk in terms of storage and using the milk.

Take advantage of the specially-made storage bags

These have two great advantages for freezing:

  • They take up less space in the freezer
  • The milk in the bags tends to thaw more quickly

That said, the soft bags do have a few disadvantages, as I explained in another post.

First in, first out rotation

Generally, use the oldest milk first. Sometimes, this is called “first in, first out.”

I do NOT recommend this strategy for babies who are premature or compromised.

Premature or compromised infants should have the fresh milk first. Why so? It best “matches” the baby’s needs, and it has not been exposed to the extreme or extended storage conditions.

Swirl the milk

Well, it does need to be “mixed”, and the usual wisdom is to swirl, not shake.

Truthfully, I’ve never seen a scrap of research to support this “swirl” mandate. But I could never bring myself to “shake” or make any vigorous motion when handling milk. Why so?

Mother’s milk is like blood. It contains live cells. We don’t shake blood. We don’t vigorously squeeze bags of blood. That’s because it, too, has live cells.

So, the moral of the story is, when handling milk, swirl it to mix.

Keep some regular bags or containers handy

Plastic bags that are specially made for milk are fine. Popular brands include Lansinoh Breastmilk Storage Bags and Medela Breast Milk Storage Bags. But as I mentioned in an earlier post, I would avoid these for premature or comprised babies.

Even the best of those bags can be easily punctured while handling milk in the freezer. (Hello! Do you have any teenagers who rummage through your freezer?) An easy way to avoid that is to put the bags into a hard container. Or, store the bags in a storage bin if you prefer to.  

Admittedly, each of these options take up more space. You might want to use them for the regular freezer, but not for the deep freezer.

It can also be a good idea to put the milk in a regular zipped bag if you’re thawing it in a bowl of water. That way, if you do lose a little milk, you can retrieve it.

Don’t overfill the container

Oddly, we all know about “head space” when using a jar or a bottle, right? We know the liquid expands in the freezer.

Why then, do parents fill the bags to the brim?

Maybe it will be just fine. But maybe it won’t.

As you are thawing an overfull bag, you may see that some milk oozes out. Just remember, that’s the creamiest part of the milk you’re losing.

Time and safety issues

Here are four easy tips to address the issues of time and safety when handling milk.

Anticipate the length of time for thawing:

There’s no real evidence for this, just a lot of experience:

  • in the refrigerator: about 12 hours
  • in a bowl of warm water: about 20 minutes
  • under warm running water: about 5-10 minutes

Hence, the fastest way to thaw the milk is the one that is often overlooked: Just putting it under warm running water. If you don’t want to stand there and hold it, prop it up in a colander.

Beware of how to keep or use the thawed milk  

Use the milk within 24 hours of when it has completely thawed.

After milk has been brought to room temperature, it’s more likely to grow harmful bacteria. That’s especially the case if the milk is kept more than 24 hours after it has been thawed.

Furthermore, if previously frozen human milk has been thawed for 24 hours, it should not be left out at room temperature for more than 2 hours.

Label the milk

Even if you don’t anticipate taking the milk outside of your home, you just never know the day when you need to do so. (See my post on natural disasters.) At a minimum, write the name, date, and phone number.

Worry less about the funny smell

Sure, it’s possible that the milk has gone sour. But that’s usually not the case.

Sometimes, milk can have “funny colors” or funny smells or funny tastes. It’s usually not a big deal.

How to “serve” the milk

There’s no one right way for how to “serve” the milk. Here are some off-beat ideas. 

What about “milksickles”?

Consider making a homemade “milksickle” or “momsickle.” But don’t improvise; check out these instructions.

Don’t bother to warm it

I had been a maternal-child nurse for decades before I came to an interesting realization.

Nowhere is it written that a baby or child “must” have their milk served warm. Many will cheerfully guzzle milk that is cool or at room temperature. Yet, some do prefer to have it warm.

However, compromised infants or those who are having difficulty gaining weight should be offered warm milk. Why so?

Likely as not, they are already struggling to maintain their body temperature, and they should not burn any extra calories to warm the milk — which is what you’re asking them to do if you give them the chilled milk.

Refreezing is pretty much verboten

We don’t have any evidence to support refreezing.

However, that doesn’t necessarily mean you need to toss it.

Truly, if you’re paying attention, you’ll realize that the baby is not going to take all the refrigerated milk within that 24-hour window.

Use it for “older baby” situations. I’ve seen parents mix it with oatmeal, or work into a pudding for an older infant. And I distinctly remember the father who mistakenly put it in his coffee when he assumed it was “creamer”!

Keep safety in mind when deciding how to handle milk, whether freezing, thawing, or storing. After that, much depends on personal preference.

What are your favorite tips for handling milk? What containers do you find useful or what other tips can you share? Tell us in the comments below.

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