How Coffee is Roasted
Whether you roast your own coffee beans or buy them from a trusted roaster, it helps to understand the basics of how coffee is roasted. Roasting transforms green coffee beans into the aromatic, flavorful beans we all know and love. Below are the main stages of the roasting process.
Slow Temperature Increase
Green coffee beans are added to a roaster and heated gradually. As the drum tumbles, the beans heat evenly. The temperature rises slowly to 460°F–530°F, allowing heat to penetrate to the bean's core without scorching the exterior.
First Color Change
As moisture is released, beans steam and begin changing color—from green to yellow to brown. This signals the start of chemical changes in the coffee’s flavor and aroma compounds.
First Crack
Once internal pressure builds, beans emit a loud cracking sound. This "first crack" marks the beginning of true roasting. The beans swell, sugars begin caramelizing, and the roast is considered complete at its lightest level.
Rapid Second Color Change
After first crack, oils rise to the surface and caramelization speeds up. Color deepens quickly. Roasters must carefully monitor time and temperature to achieve precise roast levels.
Second Crack
A second crack may occur—quieter and more subtle. Roasts beyond this point are considered dark. If roasting continues much past the second crack, bitterness increases and flavors burn off.
Stopping the Roast
Experienced roastmasters judge doneness by color, aroma, and timing. Once desired roast level is reached, the beans are cooled rapidly—usually with air or water—to halt the roast process instantly.
Degassing After Roasting
Freshly roasted coffee releases carbon dioxide (CO2) for up to 24 hours. This process, called degassing, must finish before grinding or brewing to ensure optimal flavor and aroma.
Knowing Your Coffee Roast Levels
Each roast level brings out different aspects of the coffee bean’s natural characteristics. From light and acidic to dark and full-bodied, understanding roast types helps you choose the perfect coffee for your palate.
Light Roasts
Examples: Cinnamon, Half City, New England
Light brown, dry beans with baked grain-like flavors. Higher in acidity and caffeine, lighter roasts preserve more of the coffee’s origin character.
Medium Roasts
Examples: American, City, Breakfast
Medium brown beans with balanced acidity and body. Common for professional cuppings and everyday drinking.
Medium-Dark to Dark Roasts
Examples: Full City, Viennese, Light French
Chocolate and caramel notes begin to emerge. Beans show light oil, and body becomes fuller.
Dark Roasts
Examples: French, Continental, Espresso
Dark brown, shiny beans with surface oils. Acidity decreases while bitterness and body increase. Common in espresso blends.
Very Dark Roasts
Examples: Dark French, Italian, Spanish
Nearly black beans with a smoky or charred taste. Distinct flavor of origin is mostly lost, replaced by dominant roast notes.
Conclusion: Roast with Intention
Roasting coffee is where art meets science. Every roast level brings out unique flavor nuances and aromas from the bean. Whether you’re aiming for a bright, citrusy light roast or a deep, smoky dark roast, mastering the timing, temperature, and cooling process is essential.
By understanding the crack stages, roast levels, and post-roast care like degassing, you’ll gain a greater appreciation for what goes into every cup. Whether you're roasting at home or choosing a roast profile from your favorite supplier, the knowledge of coffee roasting will elevate your entire coffee experience.
Frequently Asked Questions About Roasting Coffee
What is the first crack in coffee roasting?
The first crack is a popping sound made when coffee beans expand and moisture escapes. It marks the start of the roasting phase where beans become drinkable.
What temperature is coffee roasted at?
Coffee is typically roasted between 460°F and 530°F. The specific temperature depends on the roast profile and the desired flavor.
How long should coffee rest after roasting?
Roasted coffee should rest or “degas” for about 12–24 hours before brewing. This allows carbon dioxide to escape and improves flavor clarity.
Which roast has more caffeine—light or dark?
Light roast coffee actually contains slightly more caffeine than dark roast because roasting reduces caffeine content slightly as the beans lose density.