The following article was written in 2002 by the late Michael Sivetz, inventor of the fluid bed coffee roaster. The opinions expressed in this article are not those of coffeechemistry.com, as such we don't endorse nor deny any of its claims. This article is only meant for educational purposes.
Unlike products other food products which require minimal amounts of thermal processing, coffee undergoes a dramatic chemical changes before it even exhibits any hint of its aromatic complexity. For this to occur, we must pass the coffee over the fire, so to speak, and transform this relatively boring bean into a bean with a myriad of complexity.
The transformation from raw bean to finished product is perhaps one of the more complex stages in coffee production.
If you take a lot of green beans and smell it, it hardly has any of the characteristics that we would typically associate with roasted coffee. Yet once roasted, the raw materials within the raw bean undergo a significant transformation to give rise to hundreds of new compounds that we can appreciate.