If your milk smells or tastes soapy or metallic after time in the fridge or freezer, you may have high lipase. 

A Deeper Look:

The Issue: breast milk is naturally sweet tasting, but your milk smells and/or tastes metallic or soapy within a few hours or days of being pumped.

What To Do: the first thing you should consider is whether you are pumping under very clean conditions.  If you are confident that you are practicing good hygiene before pumping, are pumping with clean pump parts, and storing in clean containers, then it’s possible that the change is attributable to higher levels of lipase activity in your milk.  Very little research has been done on excess lipase activity, so the information below is based on what is currently believed to be true but is subject to change as—hopefully—more research is done.

For more information on cleaning your pump parts, click here.

The change in smell and taste of your milk can occur within hours of pumping or it may not be apparent until after you have thawed milk from the freezer.  The good news is that IF the change in smell or taste is attributable to excess lipase activity, the milk is still safe for your baby to consume.

Why This Change Occurs

Let’s look at why this change occurs.  Lipase is naturally found in breast milk in all mamas.  Lipase breaks down the fats in the milk and is important to helping your baby digest milk fat.  Some mamas have higher levels of lipase activity thus the fat in the milk breaks down before the baby consumes the milk.  It appears that lipase activity levels can vary from mama to mama; thus, the point that your milk may take on a different smell or taste will also vary.  Some mamas notice a change within a few hours, other do not detect a change for a few days.

Inspecting Your Milk

An easy way to prevent excess lipase activity from becoming an issue is to smell and taste your breast milk every so often after it has been expressed.  Keep track of when you inspect your milk.  If you smell or taste a change, check the last time your milk smelled fine and repeat the process, this time inspecting your milk every hour following the day and time your milk was last known to be fine.  Once you have determined when your milk changes, you know the time frame in which you should either feed freshly expressed milk to your baby or deactivate the lipase enzymes as described below.  If you do not notice a change within a week, freeze some of your milk for a week or two before thawing it and inspecting for changes, if that goes well, perhaps inspect your milk after it is frozen for a month, just to be sure (freezing can slow the breakdown of the fat but it does not stop it entirely). 

What to Do to Prevent the Change in Taste

If you do determine you have high lipase levels and you want to prevent the change in smell or taste, you can deactivate the lipase after pumping before the fats are broken down.  This is not always necessary because many babies do not care about the taste, especially if it is something they became used to early on.  To deactivate the lipase, you should scald the freshly pumped milk.  This means you should see bubbling around the edges of your pot of milk, but you should not let the milk get to a boil.  Once you see bubbling around the edges, quickly cool the milk by placing the pot into a larger bowl of ice water and then freeze the milk if you do not intend to use within a day or two.  This process is thought to destroy some of the nutrients and immunologic properties that exist in human milk; however, scalded breast milk is still believed to be a better choice over formula.  If stovetop scalding is not convenient for you, some mamas have used their bottle warmer and a thermometer to achieve the same result by heating the milk until it reaches between 160˚F and 180˚F for 30 to 60 seconds before chilling.  You may consider using a glass bottle if the idea of heating in plastic at that temperature concerns you.

If you are looking for more information on different methods to scald your milk—and a look at one mama’s journey to overcoming excess lipase activity—I highly recommend investing in Rebekah Hoffer’s book: Why Does My Breast Milk Taste Bad? It’s available as a PDF and for Kindle, and I found it to be highly informative.

Chemical Oxidation

There is also something called chemical oxidation.  Even less appears to be known on this topic.  But it is thought that a sour or rancid smell to milk, when it otherwise should not be spoiled, is due to dietary issues.  Specifically, it is thought that a mama whose diet contains polyunsaturated fats or rancid fats, or whose water has free copper or iron ions may produce milk that chemically oxidizes.  The La Leche League believes that once chemical oxidation has occurred, the milk is spoiled and should be discarded (other sources are silent on the issue or suggest the milk is fine for a baby to consume).  If you scald your milk and the milk continues to taste fine, likely you have excess lipase activity.  If you scald your milk and the milk tastes worse, you may have a chemical oxidation issue.

The EP&Me Take:

I suspect I had higher levels of lipase activity in my breast milk.  I never determined the exact point in time that my milk took on a different taste but certainly after thawing milk from the freezer, the change in smell and taste was noticeable.  I suspect that the taste of the milk began to change before I froze it, because my Little didn’t lose a beat when consuming thawed milk that definitely smelled and tasted terrible to me.  After the first month or so of pumping, my Little was consuming milk I had pumped 1-2 days prior and from the second month on, she mostly drank milk pumped 2-3 days before, so I suspect she became used to the different taste early on.

Most of the articles or research I’ve read describe the smell or taste or milk with excess lipase activity as “soapy” or “metallic”; however, a few articles described the taste with the word “vomit,” and this is the word I would use to describe how my milk tasted—it had a vomit-like aftertaste.  Now, you may be thinking, “Mama, are you SURE your milk wasn’t spoiled?” Yes, I’m positive.  I inspected the tubing on a daily basis.  I cleaned and sterilized my pump parts daily.  And I stored my milk in brand new bags designed for storing and feeding.  I also made sure that my milk was frozen or consumed by the third day after it was pumped, but more often milk was frozen or consumed a day earlier than that.  I then thought, maybe I have this other thing, this “chemical oxidation” issue.  And I suppose it’s possible that chemical oxidation was the true cause of the foul tasting milk—I have seen the word “vomit” used to describe how chemical oxidation should make milk smell or taste.  But after considering the information I could find on the topic and determining I was not consuming a single food believed to contribute to chemical oxidation or drinking water that contained free copper or iron ions, I decided chemical oxidation was unlikely.  The truth is that I don’t know.  I never scalded my milk to find out because my Little did not seemed fazed by the taste of it.  Honestly, milk was her most prized possession for the first 15 months of her life.  Even now, months later after weaning to cow milk and transitioning to sippy cups, the sight of stray a Kiinde twist bag will make her eyes light up!

If your baby does not want to consume the milk, try mixing it with a bit of fresh milk.  If your baby still refuses to consume the milk and you already have stored milk in the freezer, don’t throw it away—repurpose it!  Many mamas recommend breast milk baths for diaper rash (just cut a bag or two open and let the brick of milk melt in the bath) and other skin conditions or issues like eczema, dry skin, or bug bites.  I personally used this to treat particularly bad diaper rashes, and I think it helped.  I ran my Little’s bath as usual, added enough milk to make the water cloudy, and let her play for 15 minutes.  You can also incorporate it into foods you prepare for your baby—use it as the base or partial base to baby cereal or purees.  Some mamas have also made breast milk lotion or made breast milk soap!  Another wonderful use for your breast milk is donation to a milk bank.

Sometimes it felt to me that EPing was just one issue after another. Learning about high lipase activity was one of those times. Even though my Little still drank my milk, I constantly worried she would change her mind—I mean would you drink something tasting so bad after eating a fresh strawberry? The issues that can accompany the decision to EP are many. Hang in there mama, it will get better. May your milk be—and stay!—sweet.