Roasting 101: Development of a Profile
I was sipping my morning cup of coffee, savoring the smell and the complex flavors and wondering how they got there. How does a bag of unremarkable green beans end up tasting like this? And why are coffees so different? To answer these questions I turned to Night Owl’s Roastmaster Blake.
How does a coffee roaster figure out how to roast a particular coffee to bring out its full potential? Some beans do best at a darker roast while others lose unique origin characteristics if roasted beyond a light or medium state. Why? Let’s take a look at the roasting process to see.
Green coffee beans contain thousands of chemical compounds which when heated during roasting will react with each other to create the final flavor of the brew. There are several important temperature stages that the beans reach during the roasting process. These stages can be distinguished by color, appearance, and sound. The beans will shift from green to pale yellow to cinnamon to light brown as the roast continues. The heat expands the beans, causing cracks to appear, and more importantly, to make a distinctive popping sound. The first instance of this sound is called “first crack,” and it is a milestone in the roasting process. If the roast is stopped once first crack is complete it is called a City Roast. As roasting continues and the beans get darker and more caramelized they can reach “second crack.” Coffee taken to the second crack or slightly further can be described as a full city roast. Allowing a roast to proceed further into second crack will soon yield a much darker roast and can be described as a French roast. The speed at which these milestone temperature stages are reached and how long the beans stay there has a dramatic effect on the flavors and aromas present in the final brewed cup of coffee. Here is where the skill of the roastmaster comes into play.
Coffee is grown all over the world; each distinct region breeds unique chemical signatures requiring different roasting techniques to bring out the maximum potential. No textbook or guide is available to roasters to instruct them how to roast a particular lot of coffee. Each one is different and requires a unique roast profile. A roaster may have some starting ideas about how to handle a new type of coffee, but in reality it requires experimentation to get it really dialed in. This is the art of roasting.
How does a roastmaster create a new roast profile? You start by asking what is unique or special about the coffee. Where was it grown? How was it processed after being harvested? A dry processed Yirgacheffe and a wet processed Indonesian coffee are totally different animals and demand different roast profiles. What characteristics do we want to emphasize with each roast?
Take our Bali Blue Moon. To us, the defining aspects of this coffee are its sweetness and luxurious body. Coffee professionals refer to body as the texture or mouthfeel of the coffee. In different coffees in has been described as light, medium, heavy, silky, or tea-like. In the case of the Bali Blue Moon, is is best described as having significant weight and heavy mouthfeel. It also has a pronounced sweetness. These are the finest qualities of this coffee, and the ones we want to strengthen with the roast.
How do you bring about and maximize these qualities in this coffee? Time and temperature are the keys. A well-controlled stretching of the roast, particularly after first crack, will alter the chemical compounds in the coffee to result in the sweet and heavy-bodied cup we are after. Stretching the roast in this case means allowing somewhat more time in the roaster without allowing it to stall, or remain at too static a temperature for too long a time. A stalled roast can lead to baked, flat flavors in the final cup. Definitely not what we’re looking for.
Now you may be wondering what happens to the Blue Moon if we shorten the time up quite a bit and leave it at a lighter roast. In the grand spirit of scientific experimentation we have done this, with the following result: The sweetness and deep character of the body is greatly diminished. Instead, what results is a lemony cup with a strong herbal overtone, almost brushy. The acidity is also slightly greater. This can be quite desirable in many coffees, but in the Bali Blue Moon it doesn't match the other characteristics that develop and the resulting cup is unbalanced, uninteresting and frankly doesn't live up to the true potential of the coffee. Now you have another reason to hug your local roastmaster: they test and weed out the bad coffee so you don’t ever have to drink it.