Roasting: The Basics
It can be easy for people not steeped in specialty coffee culture to think that coffee roasting is a straight-forward art when in fact it is anything but. Variables in the roasting process can contribute to the creation of the countless flavor profiles from the same bean originating from the same farm, harvest, and lot.
There are three main roast types: light, medium and dark. Dark roast is generally roasted the longest at the highest temperature while light roast is roasted the shortest and the lowest temperature. What differentiates each roast are the time and temperature which leaves varying quantities of oil, sugar, and acidity.
If you're interested in getting to know more about the ins and outs of roasting come to one of our roasting seminars and learn from our roastmaster how it's done. Keep your eyes open for upcoming events here.
Dark roast implies most of the sugar in the bean is burned off, leaving no acidity and pulling all the oil to the surface, making for an intense and acrid tasting coffee.
Medium roast can be defined by a moderate amount of sugar and acidity remaining in the bean with no oil pulled to the surface making for a mild, smoother, and sweeter cup.
Light roast is bright, complex, with most of the sugars and acids remaining in the bean making for a vibrant cup that highlights subtle fruity and floral notes. Roasting lighter coffee requires higher quality beans and is not only harder to roast, it's harder to brew well. Roast time varies from bean to bean and roast to roast.
Next let’s get in the tools of the trade, but we must define keywords first:
Charge Temperature - Think preheat temp. in your oven. It’s start temperature of the roast when the beans are introduced to the heat source.
End of Roast Temperature - The temperature at the end of the batch.
Maillard Reaction - A complex chemical process. Can be best explained by the moment when amino acids break their bond with sugar and the sugar caramelizes. This browns the green beans and brings out the flavors and aromas you recognize as coffee.
First crack - The event at which the moisture in the bean is too hot and is released along with other gases (mainly CO2) by splitting out of the seam.
Now we’re going to walk you through a roast of our Ethiopia Guji to help you get a feel for what happens during a typical roast of one of our best coffees.
To begin we start with a higher charge temp. than a typical natural drying processed coffee because our goal is to make the total roast time shorter in order to leave more acidity in and highlight floral notes in the coffee. Once the roaster is at the charge temperature, the beans drop in. As the cool beans enter the roaster, the temperature will drop typically by 400% inside of the drum. From then, until the end of the roast, the focus is to control the rate of rise of heat in the bean to hit the End of Roast Temperature goal.
The two decisive events that occur that let you know if you’re on track, is the timing of the first crack and the Maillard reaction.
While heat begins to rise, the Maillard reaction occurs around 320 degrees. With Ethiopian coffee, we like to see this happen a little sooner to shorten the total roast time. After the Maillard reaction takes place you’re entering into the caramelization period. On this specific roast, our roaster shortens this caramelization process to produce more acidity in the bean and create a more complex final cup. This takes place up until the first crack which typically occurs around 400 degrees.
If you want a lighter roast the first crack should be sooner in the roast process depending on the batch size. From the time of the first crack to the end, the temperature is the development period. This is when the bean has lost most of its moisture, becomes sensitive to the heat, and expands in size. This development period is when the coffee develops most of its flavors. Cut this process short, the more acidity will come through in the cup. Prolong this period and you bake out the sugar and acid, creating a smoky flavored cup.
Because our Ethiopia possesses so much natural sweetness before the roast process begins, what we do is highlight the other characteristics of the bean by shortening the development period and arriving at the Maillard reaction and first crack sooner. With most coffees, you try to bring out the most sweetness that you can but with our Ethiopia, there’s no need. Finally, we end the roast at 403 degrees with the time-varying depending on batch size.
Final tasting notes of our Ethiopia Shakiso, Guji include honey, blueberry, and earl grey.
You can buy it by the pound here or come into the cafe for a pour over!