Cranberries contain a massive amount of natural pectins. They will gel all on their own, which is why you can basically make cranberry sauce out of filling.
Alton BrownBasting is evil. Basting does nothing for the meat. Why? Skin. Skin is designed to keep stuff out of the bird, so basting just lets heat out of the oven. That means the turkey will take longer to cook... so don't touch that door!
Alton Brown