Coffee roasting is a process in which heat is carefully applied to the beans to reveal the more essential elements found in the coffee beans and turn them into flavors.
Coffee roasting is to create a balanced taste and optimum taste by blending the skills of the roaster master and the data records created by software with intuition and experience.
At the start of each batch, raw “green” coffee is loaded into the roaster. In order to start the roasting process, when the indoor temperature of the roasting machine reaches the set temperature, the beans are left in the drum of the machine. Angled blades in the rotating drum swing the coffee beans towards the drum center and minimize the contact of the coffee beans with the drum wall.
In the first stage of the roasting process, a large amount of heat is applied to bring the coffee to roasting temperature. This phase should be done fast enough to retain some internal moisture, but not fast enough that the outside of the cores is at risk of burning. The color of the coffee changes from green to yellow, and the scent changes from the smell of fresh cut grass to a straw-like scent.
The required flame size, temperature value and roasting time are different for each type of coffee. The techniques adopted by the roasting master also make a difference.
Within the last 5 minutes, the coffee undergoes changes at low roasting temperatures (between 150-180 degrees). It is developed to the flavors and aromas that will occur at higher temperatures and the internal humidity, pressure and temperature are meticulously controlled.
During the last 2 to 5 minutes (depending on the type of coffee and the degree of roasting) the full taste of the coffee develops. “The first crack” occurs around 200 degrees. An explosion sound occurs as each core expands under the pressure of carbon dioxide and water vapor within it. At this point, as these gases are allowed to escape, the internal pressure drops, creating an environment with an ideal internal temperature, pressure and humidity for flavor development.
Between 180 – 200 degrees, the sugars and amino acids in the coffee react quickly to create the ultimate flavor of the coffee. The taste of coffee roasted up to a “medium roasting” degree comes from the caramelization of sugars, the reaction of sugars and amino acids. During this time, the coffee turns darker brown and the aroma turns into a nutty, cocoa-like malty character.
Each coffee has a precise final temperature and roasting time, both enhanced by a blend of intuition and experience from the roasting team.
Coffees roasted at temperatures above 200 degrees are considered dark roasted. At these temperatures, the aromas and flavors formed in the early stages burn and new aromas of fried, smoky and spicy develop. Sweet and acidic flavors are replaced by bitter flavors. Most dark roasts will develop between 210 and 215 degrees to allow the full development of these properties.