Creating food-safe silicone beads
You can use food grade silicon for casting as well as for making molds. What you need to look for is chocolate casting silicon. They are pretty expensive and there are plenty of manufacturers, but you need to follow the directions very carefully.

In Europe I have had good experience with a product called schokomold 

If you do cast silicon in a silicon mold, you can use a cooking spray as a release.

A word of caution though, the silicon is robust but it will break down over time through stretching and (chewing). You can make it more robust by adding more of the binding component, however your working time will also be reduced. Experimentation is called for.