Sunday, November 26, 2006

Unlocking the sun.

As part of my regular research into the art and science of coffee roasting, I stumbled onto a transcript of a presentation by Dr. Stanley Segall, professor of bioscience and biotechnology at Drexel University, called Physics and Chemistry of Roasting. The entire presentation was very interesting but there was one portion that really caught my attention.

"In order for a process to continue without having to put heat in, you always have to have more energy in the reactants, the bonds and the molecules that make up that seed, than you have in the products. A typical chemical reaction in which the energy of the products at that level is actually higher than the energy of the reactants is a non-spontaneous reaction. That is the kind of reaction you get when you have to put energy into a process and the process captures and retains part of that energy. In effect, the early part of the roasting process operates that way, but once you hit the point where it goes from endothermic to exothermic, then all of a sudden you have free energy. You are using the energy that the plant laid down when the plant was generating it."

I know that this is basic biophysics but I guess it never really dawned on me in such a way. When the beans enter their exothermic stage around 390F (begin producing their own heat) you are unlocking the energy stored inside the bean that was put there by the sun during the growing process! Damn! That's awesome!

The coffee plant stores a lot of energy while it's growing and the application of heat reaches a point where this energy is released.

"The amount of energy tied up in a single carbon bond can range from 80 kilocalories to 146 kilocalories per molecular bond. If you want to use up eighty kilocalories in terms of exercise, you're going to ride your bicycle for an hour. Millions of these bonds exist in the chemicals of coffee. You can begin to get some idea of how much energy is actually locked up in these bonds. So, we have a tremendously energy ladened product to begin with."

This is another example of how connected coffee is to the environment. The plant's ability to access and store energy (from the sun and nutrients) has a direct affect on our ability as roasters to access that energy and the chemical reactions (producing various flavors) produced by that energy's interaction with our energy (our roaster's heat).

Damn, I love coffee.


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