Expert: Walter Hintz - 7/13/2007

Question
Why do onions turn clearish when you cook them.  Do they have really thin cell walls or is there some kind of interesting chemical reaction taking place?

Answer
Hi Katie
Interesting question that I have never thought of before.  Yes the cell walls in an onion are very thin.  That is why we use onion to study plant cells in beginning biology.  As to why they clear when cooked I am not sure but I suspect that the stored food in the onion cells is degraded.