Changing toothpaste to a more stable structure

I am using charcoal toothpaste for an actor to spit bile on stage during a show. The paste is not the correct state for our needs. 
I know that you can freeze toothpaste and it becomes "more" solid and stable at room temperature but still not stable enough.
What organic edible compound(s) could I add to the toothpaste to make it more solid?


My previous comment that I want the toothpaste to be more solid is perhaps misleading. When I freeze the toothpaste, as one would expect, it becomes more solid due to the water content. Once removed from the freezer, the toothpaste retains a more solid form than it was in the toothpaste tube, but it does not remain as solid as I want. I was considering adding more xanthan gum powder, a stabilizer found in toothpaste. 


