Why does my bread harden faster in the fridge than in the cabinet?

I put hamburger bread in the fridge and it became hard very fast. When I leave it on the counter in a bag it stays fresh longer. I just did a experiment where i took a hog dog, put it in a plastic container, put it outside for a few days in 80 degree heat. The hot dog is starting to turn color. I think its tainted. It doesnt smell bad at all even though its rotten. Is it still edible.