The Roast Profile

The roast profile of a coffee is a term given to the time-temperature relationship of the heating of coffee bean during the roasting process. If this bean temperature is plotted on paper against time the graph like the one below results. The blue line in this graph represents the air temperature inside the roaster during the roasting process. The green line represents the temperature of the bean from the time it is loaded into the roaster to the time it is dumped into the cooling bin. This is a visual representation of the coffee roast profile.

When the coffee is first loaded into the roaster the drum and air temperature will fall sharply in the beginning as the coffee and the roaster naturally try to approach equilibrium. To roast the coffee the temperature of the air and drum must be hotter than the coffee. After about two minutes the heating of the bean and cooling of the roaster have settled. Now both the temperature of the roaster and bean increase until finished.

The shape of the curve is somewhat controlled using the amount of heat applied at different points during the roast, the amount of air flow, the amount of coffee in the roaster, the preheat temperature, etc. At the end of the roast the resulting plot represents the roast profile the coffee has followed for that particular roast.

Every roasted coffee will exhibit its most pleasing flavor and aroma in the cup when the profile follows the optimum roast profile. The roasting process can be adjusted and controlled to bring out the best in a given coffee or can fail to do so and produce a less than optimum roast. The roast profile development process will identify this optimum profile through repeated roasting and cupping of a specific coffee until the most pleasing roast profile is identified. Once determined this roast profile can be repeated for each consecutive load of coffee.

The importance of the roast profile can best be explained this way. A coffee that was roasted to a given degree of roast in 10 minutes will have a different cup profile than the same coffee roasted to the same degree of roast in 15 minutes. Also the same degree of roast for a coffee performed in the same time following a different curve will have a different cup profile as well. An enormous number of chemical reactions take place during the roasting process. When they occur and how they all interact with each other will determine the end result. By adjusting the curve the roast follows will change the point in the roast these chemical reactions occur which will effect subsequent reactions that are dependant on previous reactions. Once the optimum profile is identified it becomes the blueprint to follow to guarantee consistent results and consistent quality.

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