Is it possible to restrict the Google Speech API to only recognize from a given set of words? Alternatively, is it possible to "ban" certain words? If not, is it possible with any other speech API that supports German?

I do know that I can set hint phrases via a speech context. Still it rather recognizes a different word. 

As an example, I use the API mostly for the German language. I want to recognize the word "stärker" (which is also listed as a speech context hint), though, the API mostly transcribes it to "Stärke" unless I pronounce the "r" at the end unnaturally strong. So, is it possible to prevent the speech API from transcribing that word, for instance?

Thanks in advance!