I'm writing a scientific paper for my final year, on taste perception of particular compounds that come in contact with cells in the mouth. I'm looking for a word or short phrase to add to the word 'compounds' or 'substances' to indicate they are in the mouth, and have been put there/do not originate or naturally occur there. Words like 'masticated' that indicate the substance has been chewed are too specific (we don't have to chew to taste something), while to just say the substance 'in the mouth' with no further explanation is too vague. It's important to keep my writing concise and my word count is limited, which is why I'm trying so hard to find something appropriate.
I'm not very good at descriptive writing, grammar and vocabulary so any suggestions would be appreciated. I'm not sure if there's a more efficient way to look for words like this but I've tried several searches and the results are mostly unrelated, dirty or Nickleback.