I know this was just recently asked, but I somehow forgot to save the
answer, which I remember being "glass is best."  What is the very best
material for containers to store milk for (1) refrigerated storage,
and/or (2) frozen storage and why.  This question has come up several
times recently on Parent-L and alt.support.breastfeeding.

Rachael Hamlet
Visit the Breastfeeding Advocacy Page
  http://www.clark.net/pub/activist/bfpage/bfpage.html