It could be due to extra lipase in your breastmilk!
Lipase is an enzyme found in breastmilk that helps to break down fats so that they are easier for baby to digest.
Some mothers breastmilk has excess lipase, so when it is expressed, the lipase quickly starts to break down the fats in the milk causing the soapy smell/ taste. Some babies don’t mind the taste, while others will refuse to drink the defrosted breastmilk (like mine)!
I didn’t realize that I had excess lipase in my breastmilk until I went back to work and my husband had to feed our son the breastmilk I worked so hard to store in the freezer! He would ONLY drink fresh expressed breastmilk or breastmilk from the refrigerator. 😩
If your baby is rejecting your soapy smelling breastmilk, you can try scalding it right before freezing it. This helps to decrease the lipase in the breastmilk stopping it from breaking down the fats. After expressing you scald the milk. To do this, heat your breastmilk in a pan on the stove until you see tiny bubbles around the edges of the pan. Then let it cool and freeze like normal!
It does effect some of the nutrients and antibodies. But this shouldn’t be an issue if your baby is still eating from your breast or consuming fresh expressed breastmilk!