My Breast Milk Won’t Freeze!

You’re happily pumping to your usual routine. You throw that bag of liquid gold in the freezer, proud of what your body can make to feed your baby. But when you come back the next day the bag is still liquid. Puzzled, you hit up google only to find a few dozen other moms asking the same thing with nothing more than some Reddit and mommy group anecdotes and no actual answers.

I had a mom reach out to me with this same question. So I went back to the lactation forums only to learn has puzzled even the most experienced IBCLC lactation consultant. There is only one research study done in Spanish that has attempted to research this phenomenon. Here’s what we know:

🍷It’s not because you’ve had too much alcohol. Yes, alcohol has a lower freezing temperature, but the amount of alcohol you’d have to consume to get that level in your milk would land you in the hospital

🧊Check to make sure your freezer is at the correct temperature.

🥶The quick fix is to take the bag out of the freezer, shake it vigorously and put it back in the freezer in a single layer without it touching other bags

🍦 There are a few theories about this. One PhD chemist says it has to do with the high osmolarity of that particular milk. Basically it has extra nutrients than other milk, extra vitamins and most likely a higher fat content  it’s why it doesn’t happen all the time

🔬Dr. João Aprigio Guerra de Almeida is Coordinator of the Network of Milk Banks of Brazil and of the Ibero-American Network of milk banks. He stated:

“The fact that human milk does not freeze is associated with a phenomenon called gelation, which is autocatalytic, begins even inside the mammillary ducts, continues after extraction, and is accentuated by temperature fluctuations (heating to thaw, pasteurization and cooling) and does not disqualify the milk for consumption. 

How and why does gelation occur?

Aprigio explains:

“The milk accumulated inside the ducts, as in cases of breast engorgement, promotes pressure on the internal walls of the ducts.

On the other hand, by virtue of Isaac Newton's law of action and reaction, the ducts also promote a force on the milk – a pressure on the milk inside the ducts.

Since milk has proteins in its structure, this pressure exerted by the ducts alters the quaternary structure of the proteins, which begin to be “uncoiled or uncoiled”, assuming a more linear structure that is chemically unstable.

In search of a new stability, these proteins establish chemical bonds with the water in the milk through hydrogen bonds.

Thus, the water in human milk becomes progressively linked to the proteins, becoming imprisoned by them and, consequently, even when the temperature of the product is below the freezing point, the product does not freeze, since the water is chemically bound to the protein and for this reason fails to reorient itself to form ice crystals.

Once started, because it is an autocatalytic process, it continues. For this reason, even if the milk is kept at -18ºC in the freezer, it does not freeze, because the proteins form a network that ignites the water molecules, preventing them from coming together to form ice crystals.”

João Aprigio suggests in this situation not to think badly about milk, since it is suitable for consumption. You just have to take it out of the freezer and shake vigorously to undo the protein network that keeps the water trapped.

This may seem strange and a bit confusing, because what we usually say when the milk has been thawed for use and is ready to be fed is to shake gently. Now, when you shake the container or bag of milk it would freeze almost instantly in your hands.”

Have you ever experienced this with your milk?

The discussion by Dr. João Aprigio Guerra de Almeida is translated from Spanish from an original blog post  Click here for the original Spanish version from:

SOS, mi leche materna no se congela.