When we first started to give my daughter her solid food, we always made yum-yum noises ("mmmmm, yum yum") as a way to encourage her to eat. I guess in her mind though, that was apparently just something you did when you eat food.
One day, I was feeding her some puréed spinach. It looked pretty nasty and I'm sure it didn't taste very good either.
Despite this, she managed to take a few bites, grimacing as she did so. I tried to make the best of the situation and try to convince her it was good, but she wasn't having it.
As I gave her the second bite, she takes the spoonful, grimaces again and, as sad as a little baby can, she said "yum yum yum". Needless to say, we haven't tortured her with pure spinach again.