There will be no additives, if they simply make a crystalline form of it which rehydrates. That's the most logical way to do it.

If for some reason they think they need to have an anti-caking substance in it (which i doubt), they can use something from the GRAS (generally recognized as safe) list. No further testing involved when those are used.

But again, I think you do not understand the process. They don't need to add anything to make it a "powder" form.