During the roasting process, a green coffee bean turns from a tough untasteful bean into a tasteful aromatic coffee bean. Read here everything about the process.
The stages of coffee roasting
There are many factors that influence the roasting process of coffee beans. With careful monitoring, a coffee roaster can learn to tease out the flavors we love in coffee and avoid those we don’t. Coffee roasting is a true art. A lot can happen in twenty minutes.
Green coffee beans
Raw (green) coffee beans are small, hard and have no discernible coffee flavor. If we roast these beans, their color, structure, size, aromas and flavors will change. In a roasting machine, the coffee beans will be heated to 220°C. Variation in flavors is caused by temperature, the burning time and the air/coffee ratio in the roasting machine. A soft roasting leads to a soft, light colored coffee. A more intensive roasting leads to a strong tasteful coffee.
Drying (after 2 minutes)
After just a couple of minutes the beans will start to color as they lose moisture content. Acids are developing, but there is still no coffee aroma.
Yellowing (after 5 minutes)
The coffee beans turn from yellowish to light brown. Some toasty smells and steam will be coming off the beans as they continue to lose moisture. They will also start to swell with a build-up of gas.
First crack (after 8 minutes)
Around this time the coffee will start to pop or crack due to the pressure of gas building up inside. This is called ‘the first crack’. The beans are nearly double in size. Now the actual roasting starts at a temperature of about 200°C.
Light roast (after 10 minutes)
Just a couple minutes after the first crack a light roast is realized. The coffee roaster can choose to stop the roasting process. Brewed coffee will taste fruity or tangy with acidity.
Roast development (after 13 minutes)
Sugars will be caramelizing, and acids and other compounds are breaking down and developing flavor.
Medium roast (after 15 minutes)
After 15 minutes, the medium roast is reached. It is a well-balanced roast, lower in acidity but with a fuller body. The beans should also be dark brown with a smooth surface.
Second crack (after 18 minutes)
The bean will crack for a second time. Oils are forced to the surface and the beans will become very dark brown, glossy with oil and brittle. They will also emit a pungent smoke.
Dark roast (after 19 minutes)
After the second crack, you get an dark espresso roast. The flavor should be chocolatey and bitter. The roasting process stops at this point and the beans will be cooled and sealed.