In my experience as a newspaper reporter, the best quotes came outside the boundaries of the “formal” interview. On the record whether they realized it or not, my interviewees were more relaxed and able to provide good material while waiting for the PR assistant to show up, or walking to the elevator when the interview was over.
This is a time-tested media technique we now call the “awkward silence.” You’ve answered a question, the reporter looks down at his or her notepad, but the next question doesn’t appear to be coming. Seconds feel like days, so you decide to break the silence. That’s when you’ll likely go off track and make a statement that doesn’t quite fit your plans for the story.
If you answered the question, you answered the question. No need to dilute it just to fill space, so part of your media training should include recognizing and knowing how to deal with this tactic. Better to stumble in your conference room during a private media training session vs. when the cameras are rolling.