The Art of Roasting

Posted on: January 30th, 2013 by admin No Comments

Roasting unleashes a coffee’s potential; it is  part science part art and lots of good judgment. Roasting requires experience, concentration and precision. The art of roasting is akin to an artist’s signature on a painting, as roasting imprint the roaster’s signature on the coffee.

How bright or muted will a particular coffee be at different roast colors? How much chiaroscuro should the roaster impart to the coffee core flavor? These questions and many more are part of a roasters daily life.

Roasting with too much heat makes the beans too dark with too much caffeol (a fragrant oil produced by roasting when burnt); not enough and the caffeol is not precipitated.

Green coffee beans feel like rounded pebbles and are very hard but after roasting they become much softer and can be easily cracked by a light squeeze. They grow much larger as well, anywhere between 50-80% depending on the beans size, density and the roast color after roasting.

There are many different kinds of coffee roasters.  A classic type of roaster is the Drum Roaster which has a rotating metal drum operated by hot surfaces with heated air passing through the rotating and tumbling beans. Achieving the right balance between the conduction and convention during the roasting process is no small task but is one which is very rewarding.

The second most common roaster is the Thermal Roaster.  This type operates strictly by convection where the beans typically float on a bed of hot air and avoid touching hot surfaces. This type of roaster permits a very clean expression of the coffee flavor profile though it lacks the dimensionality that is produced in drum roasters–which impart a slight roast variation between surface and interior–achieving more depth and highlighting acidity.

During the roasting process the green coffee beans are roasted at temperatures ranging from 350º F – 460º F for 8 to 18 minutes, depending on the degree of roast required and the beans’ size and density.

During the roasting process moisture is lost from the beans, you can hear this happening, the queue is the distinct audible pops the beans makes.

Pyrolysis during roasting is a process in which starches are converted into sugar, proteins are broken down and the entire cellular structure of the bean is altered.

The roasting process develops a fine coffee’s complexity of over 600 flavor components and precipitates the release of caffeol which is the essence of the coffee we enjoy in the cup. Since it is also volatile and water soluble, once the coffee beans have been roasted, the flavor can be damaged by moisture, light and especially oxygen.