Conventions of Space and Time - S4-E3
Continuity mistake: Annie splashes Jeff in the face with a drink and she asks for two more, with Jeff still having water dripping on his face. He shouts "enough!" and suddenly his face is much drier in the next shot.
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