Thanks to all of you who gave suggestions to my queary.
Catherine, your suggestion that the fat "saponifies" gives me a good clue as to
the change that may affect a baby who is especially sensitive.  I imagine it
changes the taste...
Now to add to the suggestions:  my husband is a package engineer and suggested
another change that may be occurring in these polyethylene bags - the milk near
the bag surface may be dehydrating as polyethylene is not a good moisture
barrier.  This would cause a change in the flavor and even in the water content
of the milk.  (Remember how rubbery ice cream can get in the freezer.)
So your suggestion to keep these bags in airtight freezer containers and in a
bowl of ice if the freezer is "frost free" are very good.
Thanks again.
Jeanette Panchula, BSW, LLLL, RN, IBCLC - Puerto Rico - our "low" was 77.  Time
to go to the beach!