Admiral Slaughter: When I look at you, I no longer see students. I see seamen. From the moment you came onboard, I saw seamen inside of you. More importantly you've stopped laughing at the word "seamen" which is the mark of a true seaman.
Jeff Winger: It's the ultimate blow-off class. This class is like a redhead who likes to drink and watch Die Hard. I suggest you get her number.
Answer: It was part of the plot that when the boiled yam was dropped it looked like it was stepped on (which it never was). So there was no way to tell the difference between the flesh being soft because it was boiled or because it was stepped on (in the show that is, I don't know if one could tell the difference in real life). Plus, the rest of the yam wasn't boiled, so there was no evidence the yam was sitting in boiling water.
Bishop73