The Roast Cycle

Last month, we looked at the inception of coffee and how coffee plants evolve into green beans.
We’ll now look at what happens to the beans after they’re purchased and have arrived at our shop. The beans usually arrive in burlap bags. Larger quantities (50 lbs. or more) will come in burlap bags but will be marked on the outside with the various descriptions of the origin (countries, farm location, etc.) of the coffee.
The roast cycle, in its’ simplest form, is the heating of the green coffee bean, taking the bean and creating/altering, or balancing it in such a way to bring out the flavor, body, after taste, and acidity as desired by the roaster. Also, the acidic nature of green coffee becomes balanced by the intense heat. The heat tames the harsh acids, and intensifies the more flavorful acids.
There is a virtual symphony of activity once the beans reach a temperature of approx. 375º. The beans start turning a light brown. It is also interesting to note that if the bean structure wasn’t pliable, then the bean would explode. What’s happening is that because we’re bringing up the temperature and reworking the molecular structure of the coffee, it starts to caramelize the sugars and start a process called pyrolysis.
It’s where the sugar and the moisture split from the coffee bean and it makes a cracking noise, similar to popcorn popping.

The dark color of the coffee bean is directly related to the carmelization of sucrose in coffee. In order to maximize the the sweetness it is necessary to minimize the caramelization of sucrose. The key is to continue the roast into the City or City+ level or the bitter tasting compounds will not sufficiently degrade and the coffee will not have realized its’ full taste potential. It is suggested that unless you are intentionally roasting towards a true espresso roast that you don’t roast past the full city coloring on the chart to the left.

The key thing to remember is to stop the roast half-way between the first and second crack.