Dear Helen, When breast milk is frozen it does separate and the cream changes. I wouldn't exactly call it curdling, but it does have a rough consistancy as if the cream had separated into little tiny bits. When you shake it up, it does goes back into solution, but the graininess remains - it does not look the same as milk which had only been refrigerated and then shaken up to redistribute the cream. There is nothing wrong with it - it just looks a little funny. I always warn moms about this in class, as I did have a mom throw away all of her frozen milk once because of this. Sharon Knorr Lactation Consultant Services Rochester, New York mailto:[log in to unmask]