Oh goodness... Bleach is really powerful stuff. To remove mold, I personally use a teaspoon of bleach and fill up the rest of the bag with warm water. Let it soak for two hours. Again, rinse thoroughly. I'm glad you asked.

I haven't tried storing in the freezer, but sounds like a great idea if you're riding often. If you're not going to use it for a while, make sure you dry it using the methods described above.