The lipase mini-saga…

Breastfeeding is great…but being connected to a wee creature by the boob is not so great.  I knew that if I wanted any freedom at all in the first year, I was going to have to pump and store my milk.  And so I did.  And the little bottles and bags of boob milk populated our freezer…and all was well.

Until, I defrosted some milk that was 6 weeks old and tried to feed it to my son.  He gave me a look and screamed and refused to take it.  I don’t blame him…that milk smelled funky.  I would have refused to drink it too.  I thought that maybe my storage system was flawed.  I checked the temperature of the freezer with a snow thermometer (-20 deg C)…I expermented with freezing in different types of containers…and in different areas of the freezer.  I thought maybe it was freezer burn so I started putting containers into ziplocs…I mean, all the resources I had said frozen breastmilk was good for 4-6 months.

Then, in desperation, I did a google search for “funny smelling breastmilk” which led me to some great resources here and here.  I started to wonder, do I make excess lipase?

For those that are new to this (as I was), all human milk contains some enzymes.  Lipase chews apart fats.  If your breatmilk contains a lot of lipase, it will start to digest itself and over time that leads to a “soapy” smell.  The milk is still safe for consumption, but some babies don’t like the way it tastes or smells.  Lipase is obviously not a problem if you and your babe are going to be joined at the nip, breastfeeding on demand.  But if you are looking to store milk for any reason, it can wreck havoc on your frozen stash.  I read stories about women having to toss or donate hundreds of ounces!  Hundreds!  I felt bad enough about tossing 20 ounces.

Enzymatic reactions are temperature sensitive…lipase will chew apart human milk more quickly at room temperature than it will milk that is in the fridge or the freezer…but eventually chew it apart it will.  Lipase can be deactivated through heat…in the chem lab they call this “denaturing” a protein.  If you heat it up enough, it will unfold and loose its function but it won’t refold properly to regain function on cooling…much like cooking an egg white denatures albumin.

I could have just started scalding all of my milk, but scalding milk is time consuming and will destroy some of the good stuff in breastmilk along with the lipase…stuff like antibodies and vitamin C.  Plus, I’m a science nerd so I felt the need to do an experiment.

I pumped 4 ounces of milk and split it into two containers.  One I left alone (my control) and the other I tried to “scald.”

Scalding means to heat to just below boiling and I read that for breastmilk, 180 degrees F was the desired temperature.  I was afraid of scorching or burning the milk so I decided to use a double-boiler set up…and I used my meat thermometer which was the only kitchen thermometer I had.  And then I proceded to stand there and stir and watch….for an hour.

The milk only got to 150 degrees.  At that point, I said, screw it, and dumped it into a sauce pan and put it back on the heat.  I couldn’t use a thermometer anymore because the level of liquid was too shallow but it bubbled around the edges without coming to a full boil.  So I dumped it in a bottle and set it in an ice bath to cool rapidly.

Here are the two samples (sorry about the crappy photo):

Notice how the “scalded” sample has about half the volume?  Turns out my slow double-boiler process made a breastmilk reduction.  Mmmm mmmm yummy.

I put the two samples in the fridge on day zero and smelled them every day.  By day 3 the non-scalded sample was starting to smell a little off…but today (day 4) it was clearly skunky.

So there I had it…I had some kind of an excess enzyme problem (probably lipase) leading to accelerated breakdown of my boob milk.  Now I’m going to scald everything before I store it…and I’m really ramping up my stash as I prepare to go back to work.

Through my internet “research”, I found anecdotal evidence that breast milk could be heated to 180 degrees F to destroy the lipase or to 145 deg F for 1 minute.  Now I put my milk in a sauce pan and once it hits 145 degrees keep heating it for a minute..the process takes about 3 minutes total.  I have read some interesting things about scalding using a bottle warmer but since I don’t have a bottle warmer, I’m probably going to stick with my saucepan method for now.

I also read some anecdotal evidence (okay one posting on the LLL forum) that increasing your dietary intake of omega-3’s will decrease lipase production in boob milk…ah omegas…is there any health “problem” you haven’t been touted to fix?  Now, I don’t believe this for a minute…I need way more than one anecdote to buy into something but it did remind me that I have a bag of flax meal languishing in the fridge.  At one point I thought flax meal was good for me but for one reason or another (all of them probably related to 18 lbs of tiny human), I stopped eating it.  Now I’m adding it to all kinds of stuff.  I don’t expect this to help my lipase problem at all but it was a nice reminder to eat my flax.


  1. Welcome to the club of ladies who can’t freeze their milk! I figured it out after “only” 40 ounces. My response was to keep enough of a stash to always be a day or so ahead on milk, since I was too lazy to go through the process of scalding it. When I got too far ahead, which happened once or twice a week, I gave it away to some lady I found on the internet (no, I’m not joking). The system was a lot of work but was okay for us.
    As far as pumping enough for when you return to work, keep in mind that you’re working for just one day’s worth of milk. “Worst case” is you give your child some formula for one day, then exclusive breastmilk thereafter. It’s definitely not the end of the world!

    1. Thanks for the Welcome! Is there a club house? 🙂

      Because OR time is expensive, my work day doesn’t include things like lunch breaks. I do what I can between cases and that often includes deciding if I am going to pee or eat since I usually don’t have time for both!

      This means no time for pumping at work. I am anticipating that my supply will decrease because of this and I suspect that after a few weeks we’ll be supplementing with formula regardless…I was hoping that having a stash would help delay the inevitable.

      We’ll see how much I can milk myself over the next few weeks…at least I didn’t figure this out after going back to work!

      1. Just a quick word on the potential formula feeding situation – you might find it helpful to get your infant used to formula before hand otherwise it is possible to get the same rejection of formula that you found with frozen breast milk. If you do find it neccessary to formula feed – I found it handy (initially) to cut the formula with breast milk gradually increasing the proportion of formula used in the bottle. DD was by 10-11 months mostly on formula with just morning and bedtime feedings being breast… At the end of the day finding what works for you and your infant is all that matters, and if you find yourself knocking yourself out trying to keep the share of breastmilk high, ask yourself if it is truly really worth it, there’s more to life than being a food source after all.

        I will also note that the Fearless Formula Feeder blog has a wealth of information on the subject that is quite helpful.

        1. All good advice, thx Mrs W…

          We should join together to make a pragmatic parenting network…sort of like the holistic mom’s network but for normal people…

          1. Love, love, love this idea.

        2. Snorkel · · Reply

          Also, shop around for different formulas. I got a bunch of samples from the chemists and tried them on my baby when we had to switch to FF.

      2. Of course there’s a club house!!

        It’s funny how many people have never heard of this issue, but yet when I asked around there were several women I know who had it.

        And it’s great you figured this out now. I know of a lady who had frozen 500 ounces and had to toss out all of it. It stinks but is understandable that your job can’t allow for frequent pump breaks. I was fortunate to have a flexible office and forgiving bosses. They actually checked in with me on pumping before I even gave birth! Gotta love that.

  2. I should note that the above commentor is Mrs. W from

  3. Rebecca · · Reply

    This makes me wonder whether it’s possible to make dulce de leche from breastmilk. It would make a great topping for breastmilk ice cream, after all.

  4. miriam · · Reply

    Mega bummer. I was able to pump for 6 mo after I went back to work– even if I was “hands on” and just getting breaks from CRNAs/ fellows/ residents, I still needed a little bit of extra time just to make sure I could eat, drink, and wash my pump parts. If I was supervising, it was not unusual to have to ask someone to cover my room while I was attached to the machine. Fortunately I’m part time, so if I only got 2 sessions in over the course of the day (not counting the one when I woke up, the before bed feeding, and the late evening pump) it wasn’t a big issue.
    Breastfeeding is work.

    1. 500 ounces! OUCH.

      If I had more unscalded stored milk I would look into donating it. But it’s not that much and if I start using a bottle warmer for scalding I think I’ll use my “skunky” milk to perfect the method.

      I don’t want anyone to misunderstand, I’m not complaining about not being able to pump at work. I know what I signed up for both when I entered medicine and when I chose anesthesia. It’s great, however, that you were able to pump for so long Miriam! I may be able to find time or colleagues willing to offer me pumping breaks…we’ll see how it plays out.

      Luckily I don’t have so much lipase that I have to scald right away like some women…my milk is good refrigerated for at least 48 hours.

  5. miriam · · Reply

    I’d recommend getting some glass bottles– easier to wash and transfers heat better (I don’t know if I’d put them straight in the ice bath though). You could heat in the bottle so you could cut down on reduction– I like the bottle warmer idea for that reason too.
    I don’t suppose you have a NICU that wants breast milk?

  6. I had this problem, but I did not realize it for a very long time. My first would still drink some, would refuse some. I threw a lot away. My youngest would not touch the milk that was more than just a few hours old. And I agree, the smell is gross! I would not drink it either if I was in their position.

  7. Heather Chaney · · Reply

    Just read that flax may increase lipase problem. You may want to look into it…

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