Both the rice and the silica gel should be dried out (rejuvenated; redessicated) periodically and, if not new, dried out before first usage. Bake it in the oven (without the iPod inside and without the plastic bag) for a few hours at very low heat say 150-200 degrees.
Then take the rice (or silica) out, let it cool down, pour it back into the bag, and throw the iPod back in.
The rice can still be eaten although we suggest another drying out at the very end if not to be cooked immediately.