I've never used egg white for pouch sealing, but I would not be afraid
of insect damage.  This is because of how stable the dried white is.

"Egg tempera" (egg white mixed with pigment) has been used as a paint
medium by artists for centuries and has proven itself extremely stable
and not attractive to insects.  I know it is also (and was, I believe,
in the past) used to seal the tiny bellows in bird boxes.

Philip Jamison
West Chester, Pennsylvania