Welcome, sabalex, to DC and the ongoing Food Game---in order to play this game you take Uncle Bob's last answer of "ketchup" in response to medallions of pork and look at the last letter in ketchup. It's a "p" and then you start your answer with the letter "p".
So I will say in response to Uncle Bob's ketchup "pork tenderloin", then the next person (maybe you) will start the next word with an "N" because that's the last letter.