What fruit and vegetable turns brown and why does it turn brown?

The foods that are brown in color are: chocolate, peanut butter (they sort of have a light-brownish "tinge" but NOT exactly brown:) several types of bread, (again with the "peanut-butter reason") possibly if beans that are brown (hope they exist), brown rice, chocolate ice-cream, Chocolate Chips, (Note: I don't mean it when they are added into Chocolate Chip Cookies), and basically that's all I can think of. If any of you WikiAnswer users have more foods that are brown in color, then just add them to my list. You are welcome to do that whenever you desire!! :-)