I've been listening to the Brewing Network a LOT recently. A topic that has come up a few times in some of the podcasts is caramelization vs melanoidins. I've noticed that a lot of people are misusing the term caramelization in regards to boiling wort. I wanted to clear things up.
Caramelization is a reaction between two sugars. It occurs at temperatures above 300F in the presence of oxygen. Therefore, in a normal boil, you will NOT caramelize sugars. This also tends to happen in a dryer environment.
The browning of wort is a Maillard Reaction. This reaction is between an amino acid and sugar. It happens at lower temperatures and in a "wetter" environment. Melaniodins are produced in this reaction.
Therefore, you are not caramelizing unless you put a very small amount of wort in the kettle and reduce it down (like you would do to make caramel on the stovetop).