If you're reading this post, you're probably a bit of a coffee geek...no need to be ashamed at all, as I am a HUGE coffee geek myself. I mean, otherwise I wouldn't have become a coffee roaster and expert. ;) On today's blog, you are going to geek out with me as I explain in fairly good detail how coffee is roasted.
First, I'm going to explain how a coffee roasting machine works and how we roasters manipulate a coffee roast by utilizing the changes made available on our coffee roasting machines. A coffee roasting machine, simply called a coffee roaster, is a machine that, as you might have correctly guessed, roasts coffee. There are three common types of coffee roasters:
-Direct heat drum roasters, which use a combination of a direct fire heated drum and hot air.
-Fluid bed roasters, which use only hot air to roast.
-Indirect heat drum roasters, in which the drum is not heated, but hot air is used for roasting.
KLLR coffee has two coffee roasters, and both are direct heat drum roasters. Green coffee beans are charged into the roaster's drum or roasting chamber through a hopper, and once the coffee is done roasting it is dropped into a cooling tray with moving arms and a powerful fan that draws the heat away from the beans; once cooled, the beans are dropped into a container, usually a bucket or something similar. Modern drum roasters give us the ability to speed up or slow down a coffee roast by adjusting the heat and air flow; modern roasters also have the ability to adjust the drum speed, and while that will affect how the coffee roasts, we generally only adjust it based on coffee batch size. By having these adjustments available, we roasters can take notes and use certain parameters that we follow to help us decide how we want any coffee to be roasted, and that is what we are going to dive deep into next.
Throughout a roast, we roasters pay attention to three different phases that occur, and these are 1. the drying phase, 2. the Maillard or browning phase, 3. the development phase. By adjusting the heat and airflow, we are able to manipulate the time of each phase in order to achieve any flavor profiles we might want from any coffee. The photos shown before each of the following paragraphs show how the coffee looks at the beginning of each phase.
-Before roasting, coffee is always a green seed, very tough and very difficult to break. As it roasts, it browns, expands, and becomes more porous. During the drying phase, the coffee loses a lot of its water content, and once it loses enough water it then begins to yellow; once the coffee turns yellow and smells like bread or boiling pasta, the drying phase ends and the Maillard or browning phase begins. During the drying phase not enough chemical reactions occur that affect the flavor of the coffee, but we roasters use the drying phase to manipulate how fast or how slow we want a roast to go by either speeding up or slowing down the dry phase.
-During the Maillard or browning phase, complex chemical reactions take place, which include the development of sugars as well as chlorogenic and amino acids, all of which play important roles in the flavors that are found in coffee. By manipulating the length of this phase, roasters can bring out or mute certain flavors; a general rule, a shorter Maillard phase will retain much more fruity flavors and acidity, and the longer the phase is the more chocolate notes and the less fruit notes the coffee will present. However, if the Maillard phase is either too short or too long, then we start to get unwanted flavors in the coffee. If the phase goes too fast, the coffee might have flavors of green vegetables and the acidity will be very high; if the phase goes too slow, then the flavors in the coffee will be baked away, it will have cardboard and woodsy flavors, and the coffee will feel too heavy on the tongue. After about 3 - 4 minutes in the Maillard or browning phase, the coffee beans almost double in size and release a lot of water vapor, making a cracking sound, and it is here that the development phase of the roast begins.
-The development phase begins with the cracking of the coffee beans, what we call “first crack”; the cracking starts kind of soft, sounding like a kindling fire, and after about 20 seconds it cracks much more violently and loudly. A light roasted coffee will be ready anywhere between the very beginning of the phase until 2 - 2.5 minutes into the phase. After about 3 - 3.5 minutes, the “first crack” will end, and it is at this point that a coffee is considered a medium roast, and it will be ready between 3 - 4 minutes into the development phase. After just over 4 minutes, a “second crack” will occur, and this is caused by the release of carbon dioxide instead of water. If a coffee is allowed to reach this “second crack”, we called this a dark roast; here, roasty and smokey flavors start to develop, and the further into 2nd crack a coffee is allowed to go, the more the acidity and inherent bean flavors become muted.
During the development phase, the sugars caramelize, the acidity sweetens, and the flavors in the coffee truly emerge. Depending on the coffee and what flavors the roaster wants to achieve, the roaster decides how long the development will be. As a general rule, the shorter the development phase is the more inherent flavors and acidity are preserved, and the longer the phase is the more chocolate and caramelized sugar notes become more prevalent in the coffee. From left to right, here's how coffee looks when roasted light, medium, and dark.
Just for fun, here's what we roasters see on the computer on our end:
I hope this blog post was intriguing and informative! On part 2 of this blog, which will be released a week from this one, we are going to dive deep into how we decide how a coffee should be roasted, but for now you guys have a general idea of how we roast our coffees here at KLLR and how we make our coffees so delicious!