Why do cooked plums taste so bitter?

We couldn't answer this on the show last time, so we asked you to help. This answer came from Colleen in Michigan...

Colleen suspects it's to do with the breakdown of sugars that give that bitter taste. When you're cooking the sugars at high heat you get non-enzymatic browning, which occurs either through caramelisation or something called the Maillard reaction. That is an interaction of proteins and sugars. A free amino group of a protein reacts with a carbon-R group of a sugar, producing something called N-glycosylamine. This is unstable and is basically a downstream product. It breaks down into something called the melanoidins, which can be bitter to taste. The reactions are pretty complex, she says, and not well understood. So there could be lots of different reasons. That might be why cooking, she says, is so much of an art!