Stored breast milk is like liquid gold. You want every ounce to benefit your baby. But if you don’t know how to tell if breast milk is bad, you may end up tossing perfectly good milk, or worse, feeding your baby compromised milk.
Though there are some similarities, human milk isn’t identical to cow’s milk. Its appearance, smell, and even taste can be vastly different.
We’ve consulted the experts to bring you the following facts about breast milk storage. We’ll outline three factors you can use to identify expired breast milk so you don’t have to worry about wasting good milk or making your baby sick.
Guidelines for Storing Breast Milk
There are two phases of breast milk: “fresh” and “usable.”
Fresh milk is exactly what it sounds like — recently pumped milk at its peak of freshness, full of the nutrients and antibodies typical of breast milk.
Usable milk is past its ideal period (immediately after pumping) but still fine for your baby. It has been stored properly in the refrigerator or freezer, does not harbor bacteria, and will not threaten the health of your baby. You can guarantee nourishment to your little one, but some of the benefits may be diminished as it is no longer “fresh.”
La Leche League league gives the following guidelines for milk storage (1):
- Room temperature: 4 hours (ideal) to 6 hours (acceptable).
- Refrigerator: 72 hours (ideal) to 8 days (acceptable).
- Freezer: 3–6 months.
- Deep Freeze: 6–12 months.
The Rule Of Six
When I first visited a lactation nurse, she advised me to remember “the rule of 6.”
The rule of 6 means that breast milk can last:
- 6 hours on the counter.
- 6 days in the refrigerator.
- 6 months in the freezer.
While it’s possible that under certain circumstances my milk would last beyond those periods, the rule of 6 was an easy way to remember safe storage timelines. It helps to track guidelines and “freshness windows” when you’re caring for a newborn and mental energy might be low.
If your milk had already been nearing spoilage in the refrigerator, freezing it will buy you additional time, but it will still spoil in the freezer faster than if you had frozen it immediately after pumping.
Factors Affecting Storage Time
Two main factors impact the length of time you can effectively preserve milk: temperature and storage containers.
Milk should be stored near the back of the refrigerator, where the temperature is coldest and most stable and less affected by the opening and closing of the doors.
Milk stored in a refrigerator freezer is said to last up to six months. If you have a standalone freezer (also known as a “deep freezer” or “chest freezer”), milk can be kept for up to 12 months without spoiling because of the colder and more stable temperature.
Store your milk in commercially-made milk storage bags made specifically for freezing or in hard plastic bottles or glass baby bottles. Both should be clean and completely sealed before storing to prevent contamination, which can lead to milk spoilage.
Understanding The Smell Of Breast Milk
With regular dairy milk, the “sniff test” is often the most accurate measure of whether or not the milk has spoiled. However, with breast milk, it’s not so easy.
The scent of breast milk is easily affected, so an unfamiliar smell doesn’t automatically mean it’s gone bad. It can also vary widely from woman to woman and even change from day to day in the same person (2).
Things that affect the smell of breast milk are:
- Foods the mother has eaten.
- Medications the mother was taking.
- Freezing process.
- Storage containers.
The Taste of Breast Milk
Because smell and taste are so closely linked, the same factors that affect your milk’s smell can also affect its taste. A mother’s diet is an especially significant factor. Strong flavors, especially a “spicy” taste or pungent spices can flavor a woman’s breast milk.
Understanding The Way Breast Milk Looks
- Slightly orange.
Breast milk color can even vary within the same pumping session. Much of the variance is due to the specific ratio of foremilk to hindmilk which tends to change from morning to night. Foremilk is much thinner and more watery, whereas hindmilk is thicker and fattier.
Still, other factors like diet, medication, herbs, and hydration play a role, too. The important thing to remember is that there is a wide range of “normal,” and a shift in color of your breast milk does not automatically mean it’s bad.
What if your breast milk looks pink? It’s possible that small cracks in your nipple that may be bleeding can make your milk look very red or pink, but this milk is still safe for your baby to drink. Working with a lactation consultant can help you determine the cause for the pink milk as well as how to avoid it happening again.
Editor's Note:Michelle Roth, BA, IBCLC
Identifying Breast Milk Gone Bad
1. Look Closely
Breast milk naturally separates after pumping, with the fat rising to the top and the watery portion falling to the bottom. When milk is still good, it easily mixes with a gentle swirl of the baby bottle.
If your breast milk remains separated or chunks float in it after attempting to re-mix, it has likely gone bad and it’s a good idea to toss it.
2. Smell Your Breast Milk
If you’ve stored it in the refrigerator or at room temperature, the “sniff test” could be a reliable way to determine if your breast milk has gone bad.
This method may not be reliable, though, if you’ve frozen your breast milk. Breast milk contains lipase which breaks down fats for your baby. In mamas with high lipase breast milk, the enzyme can cause thawed breast milk to smell sour or soapy, even though it is still perfectly safe (4).
To test whether your milk tends to take on this scent, freeze a small amount of breastmilk for five days, then thaw it and smell it. Because of the short timeframe, you can be confident your milk has not soured. If it smells sour, you can know your breast milk tends to take on this smell after freezing but is still safe for your baby.
However, it’s worth noting that some babies will reject this milk. So, before freezing large batches of milk, it may be a good idea to feed some thawed milk to your baby to see whether or not they will accept it. If they won’t, you can eliminate this issue by scalding your milk before freezing.
To scald your breast milk:
- Heat your milk in a small pan.
- Wait until small bubbles form around the outside (approx. 180 degrees F).
- Remove from heat.
- Allow to cool.
- Pour into containers and freeze.
3. Taste Your Breast Milk
Similar to the previous sniff test, taste your breast milk. It will taste different than cow’s milk, but any flavor other than rancid/sour is acceptable.
If you store your milk in the refrigerator and it tastes rancid or sour, it has likely gone bad and should not be fed to your baby.
In the case of frozen milk, see the above steps to determine whether your milk tends to take on a sour (but safe) flavor upon freezing due to high lipase. If this isn’t the case, but your milk tastes sour in one particular instance, throw away the milk as it has likely gone bad.
Has Your Milk Gone Bad?
You work so hard to pump your milk, you don’t want a drop to go to waste. Following proper storage recommendations and understanding the variances in the appearance, smell, and taste of breast milk can prevent you from unnecessarily throwing out otherwise good milk.
You need to be sure that the milk you’re feeding your babe won’t make them sick, and knowing how to test it for spoilage will do just that.